Impact of extreme high temperature on mortality and regional level definition of heat wave: a multi-city study in China

Combined effect of heatwaves and residential greenness on the risk of stroke among Chinese adults: A national cohort study

Heatwaves have been associated with an increased risk of stroke, while residential greenness may offer protective benefits. This prospective cohort study examined 22,702 participants aged 35 years or older, with no prior history of cardiovascular disease (CVD), from the China Hypertension Survey (CHS) conducted between 2012 and 2015. Participants were followed up between 2018 and 2019. Heatwaves were defined as daily maximum temperatures exceeding the 92.5th percentile of the warm season for at least three consecutive days. Residential greenness was quantified using the Normalized Difference Vegetation Index (NDVI) within buffers of 300, 500, and 1000 m from participants' residences. Multivariable Cox proportional hazards models evaluated the independent and combined effects of heatwaves and greenness on stroke risk, while restricted cubic spline analyses explored nonlinear relationships. Interaction effects were assessed using both multiplicative and additive Cox regression models. During follow-up, 597 stroke events occurred. Each additional 3-day increase in heatwave days was associated with an increased stroke risk (HR: 1.19, 95 % CI: 1.08-1.31). Interaction analyses demonstrated a synergistic effect between heatwaves and lower residential greenness (NDVI300 m, NDVI500 m and NDVI1000 m) on stroke risk, with significant additive(RERI > 0, P < 0.05) and multiplicative interactions (HR > 1, P < 0.05). The strongest protective effects of greenness were observed within a 500 m buffer zone, particularly for individuals under 60 years, rural residents, and those with higher educational attainment. This study highlights the potential benefits of enhancing greenness for cardiovascular health and provides valuable insights for environmental governance and public health policy in China.

A new approach to estimate the heat thresholds at the county level in China

BACKGROUND

High temperature beyond the comfort threshold is the main hazard to cause heat-related mortality. However, existing methods of defining the heat thresholds are usually based on case studies in data-rich regions and rarely considers the acclimatization.

METHODS

Based on the temperature-mortality relationship observed in 36 locations covering all six major climate zones in China, we found that the relative risk (RR) of heat-related mortality and the annual frequency of temperature (AFT) have a power function relationship (adjusted R2 = 0.74)), and the association is independent to the variation of the temperature across the territory. Furthermore, the association is slightly changed when the GDP/capita, proportion of elderly population and latitude are adjusted. According to this association, we proposed a new method to choose the heat threshold at finer resolution using only AFT. As the temperature frequency is easy to calculate, this method can be promoted to any geographical location without mortality data.

RESULTS

According to the relationship between AFT and RR, using the daily time series of temperature at 2405 observation stations in China, we estimated and mapped the distribution of heat thresholds at the county level across China. We find that when the AFT is just 1 day per year, the corresponding RR is approximately 1.4 (95% CI, 1.2-1.8). As the AFT increases to 5 days per year, the RR decreases to about 1.2 (95% CI, 1.1-1.3). When the AFT reached 10 days per year, the RR further decreased to about 1.05 (95% CI, 1.0-1.1).

CONCLUSIONS

This study advances the understanding on the driver of human beings' adaptation to high temperature. It also contributes significantly to the research on heat-related mortality in the context of global climate change.

Heat wave, fine particulate matter, and cardiovascular disease mortality: A time-stratified case-crossover study in Shenzhen, China

BACKGROUND

In the context of global warming, the frequency of heat wave and the concentration of fine particulate matter (PM2.5) have increased, and more people are co-exposed to air pollution and extreme heat. However, the interaction between heat wave and PM2.5 on cardiovascular disease (CVD) mortality remained largely unknown.

METHODS

We conducted a time-stratified case-crossover study of 40,169 CVD deaths in Shenzhen, China between 2013 and 2022. Meteorological data and air pollutants information were obtained based on the residential addresses from the validated grid datasets. A total of 21 heat wave definitions were constructed using various relative temperature thresholds and durations. Conditional logistic regression was used to evaluate the independent and interactive effects of exposure to heat wave and PM2.5 on CVD mortality.

RESULTS

The odds ratios (ORs) and 95 % confidence intervals (CIs) for CVD mortality associated with heat waves ranged from 1.17 (95 % CI: 1.001,1.36) to 1.91 (95 % CI: 1.42, 2.56). For every increase of 10 µg/m³ in PM2.5 exposure, the ORs (95 % CI) for CVD mortality ranged from 1.0283 (95 % CI: 1.0162, 1.0406) to 1.029 (95 % CI: 1.0169, 1.0413). There was a synergistic effect between heat wave and PM2.5 exposures on CVD mortality. It was estimated that up to 2.03 % of CVD deaths were attributable to heat wave and PM2.5 levels exceeding the interim target 4 in the World Health Organization air quality guidelines (≥ 25 μg/m3), resulting in 816 premature deaths. Females and individuals over 75 years old were vulnerable populations.

CONCLUSIONS

Heat wave and PM2.5 exposures individually and synergistically contributed to increased risks of CVD mortality. Our findings indicate that reducing exposure to both heat wave and PM2.5 may yield significant health benefits and prevent a significant portion of premature deaths from CVDs.

Heatwave and upper urinary tract stones morbidity: effect modification by heatwave definitions, disease subtypes, and vulnerable populations

As heatwave occurs with increased frequency and intensity, the disease burden for urolithiasis, a heat-specific disease, will increase. However, heatwave effect on urolithiasis subtypes morbidity and optimal heatwave definition for urolithiasis remain unclear. Distributed lagged linear models were used to assess the associations between 32 defined heatwave and upper urinary tract stones morbidity. Relative risk (RR) and attributable fraction (AF) of upper urinary tract stone morbidity associated with heatwave of different intensities (low, middle, and high) were pooled by meta-analysis. Optimal heatwave definition was selected based on the combined score of AF, RR, and quasi-Akaike Information Criterion (QAIC) value. Stratified analyses were conducted to investigate the modification effects of gender, age, and disease subtypes. Association between heatwave and upper urinary tract stones morbidity was mainly for ureteral calculus, and AF was highest for low-intensity heatwave. This study's optimal heatwave was defined as average temperature > 93rd percentile for ≥ 2 consecutive days, with AF of 7.40% (95% CI: 2.02%, 11.27%). Heatwave was associated with ureteral calculus morbidity in males and middle-aged adults. While heatwave effect was statistically insignificant in females and other age groups. Managers should develop appropriate definitions to address heatwave based on regional characteristics and focus on heatwave effects on urolithiasis.

Health risks from extreme heat in China: Evidence from health insurance

Global warming has accentuated the effects of extreme heat on health. Health insurance, functioning as a risk management tool, has the potential to alleviate these impacts. Consequently, this paper investigates the correlation between extreme heat events and the demand for health insurance in China. Using data from the China Health and Nutrition Survey, we have observed a substantial increase in the likelihood of residents purchasing health insurance during extreme heat events. To be specific, for every extra day of extreme heat events annually, there is a 0.3% increase in the probability of purchasing health insurance. This effect is not uniform across different demographic groups. It is particularly pronounced among middle-aged and elderly individuals, rural residents, those with lower educational levels, higher income brackets, and individuals residing in underprivileged areas with limited access to green spaces and healthcare facilities. Furthermore, our study indicates that the increased frequency of extreme heat events not only impacts individuals' physical health but also triggers negative emotions, which in turn drive risk-averse behavior related to health insurance purchases. These findings carry substantial policy implications for mitigating the economic consequences of climate change.

The influence of humid heat on morbidity of megacity Shanghai in China

BACKGROUND

Increased attention has been paid to humid-heat extremes as they are projected to increase in both frequency and intensity. However, it remains unclear how compound extremes of heat and humidity affects morbidity when the climate is projected to continue warming in the future, in particular for a megacity with a large population.

METHODS

We chose the Wet-Bulb Globe Temperature (WBGT) index as the metric to characterize the humid-heat exposure. The historical associations between daily outpatient visits and daily mean WBGT was established using a Distributed Lag Non-linear Model (DLNM) during the warm season (June to September) from 2013 to 2015 in Shanghai, a prominent megacity of China. Future morbidity burden related to the combined effect of high temperature and humidity were projected under four greenhouse gases (GHGs) emission scenarios (SSP126, SSP245, SSP370 and SSP585).

RESULTS

The humid-heat weather was significantly associated with a higher risk of outpatient visits in Shanghai than the high-temperature conditions. Relative to the baseline period (2010-2019), the morbidity burden due to humid-heat weather was projected to increase 4.4 % (95 % confidence interval (CI): 1.1 %-10.1 %) even under the strict emission control scenario (SSP126) by 2100. Under the high-GHGs emission scenario (SSP585), this burden was projected to be 25.4 % (95 % CI: 15.8 %-38.4 %), which is 10.1 % (95 % CI: 6.5 %-15.8 %) more than that due to high-temperature weather. Our results also indicate that humid-hot nights could cause large morbidity risks under high-GHGs emission scenarios particularly in heat-sensible diseases such as the respiratory and cardiovascular disease by the end of this century.

CONCLUSIONS

Humid heat exposures significantly increased the all-cause morbidity risk in the megacity Shanghai, especially in humid-hot nights. Our findings suggest that the combined effect of elevated temperature and humidity is projected to have more substantial impact on health compared to high temperature alone in a warming climate.

The association of heatwave with drowning mortality in five provinces of China

Drowning is a serious public health problem in the world. Several studies have found that ambient temperature is associated with drowning, but few have investigated the effect of heatwave on drowning. This study aimed to explore the associations between heatwave and drowning mortality, and further estimate the mortality burden of drowning attributed to heatwave in China. Drowning mortality data were collected in 71 prefectures in China during 2013-2018 from provincial vital register system. Meteorological data at the same period were collected from European Centre for Medium-Range Weather Forecasts (ECMWF). A distributed lag non-linear model (DLNM) was first to explore the association between heatwave and drowning mortality in each prefecture. Secondly, the prefecture-specific associations were pooled using meta-analysis. Finally, attributable fractions (AFs) of drowning deaths caused by heatwave were estimated. Compared to normal day, the mortality risk of drowning significantly increased during heatwave (RR = 1.20, 95%CI: 1.18-1.23). Higher risks were observed in males (RR = 1.23, 95%CI: 1.20-1.27) than females (RR = 1.18, 95%CI: 1.13-1.23), in children aged 5-14 years old (RR = 1.24, 95%CI: 1.15-1.33) than other age groups, in urban city (RR = 1.32, 95%CI: 1.28-1.36) than rural area (RR = 1.09, 95%CI: 1.07-1.12) and in Jilin province (RR = 2.85, 95%CI: 1.61-5.06) than other provinces. The AF of drowning deaths due to heatwave was 11.4 % (95%CI: 10.0 %-12.9 %) during heatwave and 1.0 % (95%CI: 0.9 %-1.1 %) during study period, respectively. Moreover, the AFs during study period were higher for male (1.2 %, 95%CI: 1.0 %-1.3 %), children 5-14 years (1.1 %, 95%CI: 0.7 %-1.6 %), urban city (1.6 %, 95%CI: 1.4 %-1.8 %) than their correspondents. These differences were also observed in AFs during heatwave. We found that heatwave may significantly increase the mortality risk of drowning mortality, and its mortality burden attributable to heatwave was noteworthy. Targeted intervention should be carried out to decrease drowning mortality during heatwave.

Temporal and spatial characteristics of high temperatures, heat waves, and population distribution risk in China from 1951 to 2019

Understanding the relationships between high temperatures (HT) and heat waves (HW) is vital for enhancing human health, especially in areas with dense population. This paper analyzes the temporal and spatial characteristics of different HT and HW intensities, their spatial influence, and the population distribution risk at different HW intensities for 844 meteorological stations between 1951 and 2019. The results indicate that (1) HT and extreme temperature (ET) days are symmetrically distributed along the Huhuanyong Line, from southeast to northwest China. The times, days, and accumulated temperatures of HW, the times, days, and accumulated temperature of strong heat waves (SHW), and the times, days, and accumulated temperature of extreme heat waves (EHW) were distributed similarly; (2) with the increase in high temperatures or heat waves from HT to ET or from HW to SHW, the proportion of stations with an upward trend was always greater in China, while stations with a downward trend were mainly located in the North China Plain and Huai River Basin. For HW, SHW, and EHW, the increasing range of times and days were less than the accumulated temperatures; (3) between 1990 and 2019, there was an expansion of the HW and SHW distribution area with an annual average of more than 10 days, and the EHW distribution area with an annual average of more than 3 days. Moreover, the number of people exposed to HW, SHW, and EHW also increased during this period; and (4) considering the population distribution characteristics and the regional HT and HW characteristics, society needs to form regional adaptation actions for different HT and HW intensities.

Exploration of the preterm birth risk-related heat event thresholds for pregnant women: a population-based cohort study in China

Background

Heat events increase the risk of preterm birth (PTB), and identifying the risk-related event thresholds contributes to developing early warning system for pregnant women and guiding their public health response. However, the event thresholds that cause the risk remain unclear. We aimed to investigate the effects of heat events defined with different intensities and durations on PTB throughout pregnancy, and to determine thresholds for the high-risk heat events.

Methods

Using a population-based birth cohort data, we included 210,798 singleton live births in eight provinces in China during 2014-2018. Daily meteorological variables and inverse distance weighted methods were used to estimate exposures at a resolution of 1 km × 1 km. A series of cut off temperature intensities (50th-97.5th percentiles, or 18 °C-35 °C) and durations (at least 1, 2, 3, 4 or 5 consecutive days) were used to define the heat events. Cox regression models were used to estimate the effects of heat events on PTB in various gestational weeks during the entire pregnancy, and event thresholds were determined by calculating population attributable fractions.

Findings

The hazard ratios of heat event exposure on PTB ranged from 1.07 (95% CI: 1.00, 1.13) to 1.43 (1.15, 1.77). Adverse effects of heat event exposure were prominently detected in gestational week 1-4, week 21-32 and the four weeks before delivery. The heat event thresholds were determined to be daily maximum temperature at the 90th percentile of the distribution or 30 °C lasting for at least one day. If pregnant women were able to avoid the heat exposures from the early warning systems triggered by these thresholds, approximately 15% or 17% of the number of total PTB cases could have been avoided.

Interpretation

Exposure to heat event can increase the risk of PTB when thermal event exceeds a specific intensity and duration threshold, particularly in the first four gestational weeks, and between week 21 and the last four weeks. This study provides compelling evidence for the development of heat-health early warning systems for pregnant women that could substantially mitigate the risk of PTB.

Funding

National Key R&D Program of China (No. 2018YFA0606200), National Natural Science Foundation of China (No. 42175183), Sanming Project of Medicine in Shenzhen (No. SZSM202111001).

Short-term exposure to temperature and mental health in North Carolina: a distributed lag nonlinear analysis

Adverse mental health outcomes have been associated with high temperatures in studies worldwide. Few studies explore a broad range of mental health outcomes, and to our knowledge, none are specific to NC, USA. This ecological study explored the relationship between ambient temperature and mental health outcomes (suicide, self-harm and suicide ideation, anxiety and stress, mood disorders, and depression) in six urban counties across the state of NC, USA. We applied a quasi-Poisson generalized linear model combined with a distributed lag nonlinear model (DLNM) to examine the short-term effects of daily ambient temperature on emergency admissions for mental health conditions (2016 to 2018) and violent deaths (2004 to 2018). The results were predominately insignificant, with some key exceptions. The county with the greatest temperature range (Wake) displays higher levels of significance, while counties with the lowest temperature ranges (New Hanover and Pitt) are almost entirely insignificant. Self-harm and suicidal ideation peak in the warm months (July) and generally exhibit a protective effect at lower temperatures and shorter lag intervals. Whereas anxiety, depression, and major depressive disorders peak in the cooler months (May and September). Suicide is the only outcome that favored a 20-day lag period in the sensitivity analysis, although the association with temperature was insignificant. Our findings suggest additional research is needed across a suite of mental health outcomes to fully understand the effects of temperatures on mental health.

Heatwave and urinary hospital admissions in China: Disease burden and associated economic loss, 2014 to 2019

BACKGROUND

Many studies have shown that heatwaves are associated with an increased prevalence of urinary diseases. However, few national studies have been undertaken in China, and none have considered the associated economic losses. Such information would be useful for health authorities and medical service providers to improve their policy-making and medical resource allocation decisions.

OBJECTIVES

To explore the association between heatwaves and hospital admissions for urinary diseases and assess the related medical costs and indirect economic losses in China from 2014 to 2019.

METHODS

Daily meteorological and hospital admission data from 2014 to 2019 were collected from 23 study sites with different climatic characteristics in China. We assessed the heatwave-hospitalization associations and evaluated the location-specific attributable fractions (AFs) of urinary-related hospital admissions due to heatwaves by using a time-stratified case-crossover method with a distributed lag nonlinear model. We then pooled the AFs in a meta-analysis and estimated the national excess disease burden and associated economic losses. We also performed stratified analyses by sex, age, climate zone, and urinary disease subtype.

RESULTS

A significant association between heatwaves and urinary-related hospital admissions was found with a relative risk of 1.090 (95 % confidence interval (CI): 1.050, 1.132). The pooled AF was 8.27 % (95%CI: 4.77 %, 11.63 %), indicating that heatwaves during the warm season (May to September) caused 248,364 urinary-related hospital admissions per year, with 2.42 (95%CI: 1.35, 3.45) billion CNY in economic losses, including 2.23 (95%CI: 1.29, 3.14) billion in direct losses and 0.19 (95%CI, 0.06, 0.31) billion in indirect losses, males, people aged 15-64 years, residents of temperate continental climate zones, and patients with urolithiasis were at higher risk.

CONCLUSION

Tailored community health campaigns should be developed and implemented to reduce the adverse health effects and economic losses of heatwave-related urinary diseases, especially in the context of climate change.

Analysis of time-dependent effects of ambient temperatures on health by vulnerable groups in Korea in 1999-2018

This study compared the relative risks of heat days on mortalities by vulnerable groups (elderly, single-person households, less-educated) in the past decade (1999-2008) and the recent decade (2009-2018) in four cities, Seoul, Incheon, Daegu, and Gwangju, in Korea. It has been known that the health impacts of heatwaves have gradually decreased over time due to socio-economic development, climate adaptation, and acclimatization. Contrary to general perception, we found that the recent relative risk of mortality caused by heat days has increased among vulnerable groups. It may associate with recent increasing trends of severe heat days due to climate change. The increasing relative risk was more significant in single-person households and less-educated groups than in the elderly. It implies that the impacts of climate change-induced severe heat days have been and will be concentrated on vulnerable groups. It suggests that social polarization and social isolation should be addressed to reduce heatwave impacts. Furthermore, this study shows the necessity of customized heatwave policies, which consider the characteristics of vulnerable groups.

Systematic identification of heat events associated with emergency admissions to enhance the heat-health action plan in a subtropical city: a data-driven approach

According to the United Nations Office for Disaster Risk Reduction (UNDRR), a heat-health action plan should address various impacts of hazards at different levels, including an early warning system to monitor risks and behaviour enhancement to increase disaster preparedness. It is necessary to comply with guidelines regarding heat duration/intensity. In this study, we developed a data-driven approach to rapidly and systematically estimate the impacts of various heat events on emergency admissions among the adult population (n = 7,086,966) in Hong Kong in order to enhance the heat-health action plan. Immediate, short-term, and long-term impacts determined by 1-day, 4-day, and 8-day windows were estimated to identify specific heat events suitable for early warnings. In addition, underestimated risk, determined by a continuous increase in heat risk after days without significant emergency admissions, was estimated to evaluate potential maladaptive behaviours among a specific subpopulation. Based on age- and gender-specific analyses, 1D, 1D1N, and 2D2N were observed to have a stronger immediate impact on emergency admissions. 1D1N and 2D2N also showed notable short-term and long-term impacts. Based on heat vulnerability factors (age and gender), 2D2N was a higher-priority extreme heat event for early warning measures than 1D1N. Furthermore, men aged 19 to 64 had the highest underestimated risk. Specifically, they had IRR values of 1.113 [1.087, 1.140], 1.061 [1.035, 1.087], and 1.069 [1.043, 1.095] during lag days 3-5 of 3D2N, respectively, possibly due to a lack of adaptive behaviour. By adopting our approach, the duration of heat events with significant health impacts can be identified in order to further enhance relevant heat stress information. This framework can be applied to other cities with a similar background for rapid assessment.

Photosystem II photochemical adjustment of tall fescue against heat stress after melatonin priming

High temperature is the key factor restricting the survival of tall fescue. Extreme summer hot events arise from global warming further increases this risk. As a candidate chemical priming agent previously reported, melatonin offers innovative solution to improve heat resistance of plants. However, the mechanistic insight remains ill-defined, especially in PSII photochemical reactions. In this study, we investigated the effect of melatonin priming on photosynthetic electron transport of PS II against heat stress in tall fescue. Results showed that melatonin weakened the electron transfer efficiency of PS II per light reaction center (RC) at donor-side and receptor-side, while increased the number of RC per unit cross-sectional area. The quenching analysis further revealed that the proportion of photochemical quenching, Y(II), increased by melatonin. Considering the enriched chl a and nonevent oxidative damage, we argued that inefficient but more abundant RC introduced by melatonin protected the PSII from oxidative damage under heat stress. Notably, these effects were dependent on melatonin concentration but not temperature, an optimal application concentration (50 μmol/L) was uncovered. Besides, melatonin decreased NPQ and encouraged reverse reaction of the xanthophyll cycle. We proposed that melatonin prevents the production of excessive excitation energy. In brief, melatonin plays a distinctive role in regulating photoelectric conversion of PSII of tall fescue under heat stress, increased its survival rate after heat shock.

Urban Air Pollution, Urban Heat Island and Human Health: A Review of the Literature

Many cities of the world suffer from air pollution because of poor planning and design and heavy traffic in rapidly expanding urban environments. These conditions are exacerbated due to the Urban Heat Island (UHI) effect. While there have been studies linking the built environment and air pollution with health, they have ignored the aggravating role of UHI. The past urban planning literature in this field has also ignored the science of materials, vehicles and air pollution, and technological solutions for reducing cumulative health impacts of air pollution and UHI. Air Pollution, built environment and human health are complex discussion factors that involve several different fields. The built environment is linked with human health through opportunities of physical activity and air quality. Recent planning literature focuses on creating compact and walkable urban areas dotted with green infrastructure to promote physical activity and to reduce vehicle emission-related air pollution. Reduced car use leading to reduced air pollution and UHI is implied in the literature. The literature from technology fields speaks to the issue of air pollution directly. Zero emission cars, green infrastructure and building materials that absorb air pollutants and reduce UHI fall within this category. This paper identifies main themes in the two streams of urban air pollution and UHI that impact human health and presents a systematic review of the academic papers, policy documents, reports and features in print media published in the last 10–20 years.

Population Exposure Changes to One Heat Wave and the Influencing Factors Using Mobile Phone Data—A Case Study of Zhuhai City, China

The frequent occurrence of extreme high temperature weather and heat waves has greatly affected human life. This paper analyzes population exposure and its influencing factors during a heat wave incident in Zhuhai from 6 to 12 September 2021 based on real-time mobile phone data and meteorological data. The results show that the most areas of Zhuhai are affected by high temperature during this heat wave incident. The hourly population exposure is directly proportional to hourly heat wave coverage. In terms of time dimension, the overall population exposure shows a trend of decreasing and then increasing. In terms of spatial dimensions, high population exposure is concentrated in areas such as primary and secondary schools, colleges and universities, office buildings, and residential areas. Low exposure is distributed in most of the mountainous areas along the southern coast. In addition, the leading factors that cause changes in population exposure in different periods of the heat wave cycle are different, which rely more on either climatic factors or population factors.

Extreme Weather Conditions and Cardiovascular Hospitalizations in Southern Brazil

This research concerns the identification of a pattern between the occurrence of extreme weather conditions, such as cold waves and heat waves, and hospitalization for cardiovascular diseases (CVDs), in the University Hospital of Santa Maria (HUSM) in southern Brazil between 2012 and 2017. The research employed the field experiment method to measure the biometeorological parameters associated with hospital admissions in different seasons, such as during extreme weather conditions such as a cold wave (CW) or a heat wave (HW), using five thermal comfort indices: physiologically equivalent temperature (PET), new standard effective temperature (SET), predicted mean vote (PMV), effective temperatures (ET), and effective temperature with wind (ETW). The hospitalizations were recorded as 0.775 and 0.726 admissions per day for the winter and entire study periods, respectively. The records for extreme events showed higher admission rates than those on average days. The results also suggest that emergency hospitalizations for heart diseases during extreme weather events occurred predominantly on days with thermal discomfort. Furthermore, there was a particularly high risk of hospitalization for up to seven days after the end of the CW. Further analyses showed that cardiovascular hospitalizations were higher in winter than in summer, suggesting that CWs are more life threatening in wintertime.

Using machine learning to examine street green space types at a high spatial resolution: Application in Los Angeles County on socioeconomic disparities in exposure

BACKGROUND

Compared to commonly-used green space indicators from downward-facing satellite imagery, street view-based green space may capture different types of green space and represent how environments are perceived and experienced by people on the ground, which is important to elucidate the underlying mechanisms linking green space and health.

OBJECTIVES

This study aimed to evaluate machine learning models that can classify the type of vegetation (i.e., tree, low-lying vegetation, grass) from street view images; and to investigate the associations between street green space and socioeconomic (SES) factors, in Los Angeles County, California.

METHODS

SES variables were obtained from the CalEnviroScreen3.0 dataset. Microsoft Bing Maps images in conjunction with deep learning were used to measure total and types of street view green space, which were compared to normalized difference vegetation index (NDVI) as commonly-used satellite-based green space measure. Generalized linear mixed model was used to examine associations between green space and census tract SES, adjusting for population density and rural/urban status.

RESULTS

The accuracy of the deep learning model was high with 92.5% mean intersection over union. NDVI were moderately correlated with total street view-based green space and tree, and weakly correlated with low-lying vegetation and grass. Total and three types of green space showed significant negative associations with neighborhood SES. The percentage of total green space decreased by 2.62 [95% confidence interval (CI): -3.02, -2.21, p < 0.001] with each interquartile range increase in CalEnviroScreen3.0 score. Disadvantaged communities contained approximately 5% less average street green space than other communities.

CONCLUSION

Street view imagery coupled with deep learning approach can accurately and efficiently measure eye-level street green space and distinguish vegetation types. In Los Angeles County, disadvantaged communities had substantively less street green space. Governments and urban planners need to consider the type and visibility of street green space from pedestrian's perspective.

The association between extreme temperature and pulmonary tuberculosis in Shandong Province, China, 2005-2016: a mixed method evaluation

BACKGROUND

The effects of extreme temperature on infectious diseases are complex and far-reaching. There are few studies to access the relationship of pulmonary tuberculosis (PTB) with extreme temperature. The study aimed to identify whether there was association between extreme temperature and the reported morbidity of PTB in Shandong Province, China, from 2005 to 2016.

METHODS

A generalized additive model (GAM) was firstly conducted to evaluate the relationship between daily reported incidence rate of PTB and extreme temperature events in the prefecture-level cities. Then, the effect estimates were pooled using meta-analysis at the provincial level. The fixed-effect model or random-effect model was selected based on the result of heterogeneity test.

RESULTS

Among the 446,016 PTB reported cases, the majority of reported cases occurred in spring. The higher reported incidence rate areas were located in Liaocheng, Taian, Linyi and Heze. Extreme low temperature had an impact on the reported incidence of PTB in only one prefecture-level city, i.e., Binzhou (RR = 0.903, 95% CI: 0.817-0.999). While, extreme high temperature was found to have a positive effect on reported morbidity of PTB in Binzhou (RR = 0.924, 95% CI: 0.856-0.997) and Weihai (RR = 0.910, 95% CI: 0.843-0.982). Meta-analysis showed that extreme high temperature was associated with a decreased risk of PTB (RR = 0.982, 95% CI: 0.966-0.998). However, extreme low temperature was no relationship with the reported incidence of PTB.

CONCLUSION

Our findings are suggested that extreme high temperature has significantly decreased the risk of PTB at the provincial levels. The findings have implications for developing strategies to response to climate change.

A Comparative Assessment of Cooling Center Preparedness across Twenty-Five U.S. Cities

Cooling centers have played a significant role in reducing the risks of adverse health impacts of extreme heat exposure. However, there have been no comparative studies investigating cooling center preparedness in terms of population coverage, location efficiency, and population coverage disparities among different subpopulation groups. Using a catchment area method with a 0.8 km walking distance, we compared three aspects of cooling center preparedness across twenty-five cities in the U.S. We first calculated the percentage of the population covered by a single cooling center for each city. Then, the extracted values were separately compared to the city's heat indexes, latitudes, and spatial patterns of cooling centers. Finally, we investigated population coverage disparities among multiple demographics (age, race/ethnicity) and socioeconomic (insurance, poverty) subpopulation groups by comparing the percentage of population coverage between selected subpopulation groups and reference subpopulation groups. Our results showed that cooler cities, higher latitude cities, and cities with dispersed cooling centers tend to be more prepared than warmer cities, lower latitude cities, and cities with clustered cooling centers across the U.S. Moreover, older people (≥65) had 9% lower population coverage than younger people (≤64). Our results suggest that the placement of future cooling centers should consider both the location of other nearby cooling centers and the spatial distribution of subpopulations to maximize population coverage and reduce access disparities among several subpopulations.

Urban Thermal Characteristics of Local Climate Zones and Their Mitigation Measures across Cities in Different Climate Zones of China

Understanding the urban thermal environment is vital for improving urban planning and strategy development when mitigating urban heat islands. However, urban thermal characteristics of local climate zones (LCZ) are different within cities and most studies lack regional perspective. This study explored surface thermal performances of cities in three urban agglomerations (Jing-Jin-Ji, Yangtze River Delta and Pearl River Delta) in China using MODIS land surface temperature (LST). Besides that, the diurnal and seasonal LST variations of LCZs are also studied. Moreover, the optimal LCZs for better urban cooling are also investigated in this study. Although the thermal distributions of LCZs are different in China, there are still some similar features. Our four key findings were as follows. (1) LCZs in China are well classified, with average overall accuracy of 82% being higher than that in some previous studies. (2) The LST of mid-rise (LCZ 2, 5) is higher than that of high- and low-rise buildings (LCZ 1, 3, 4, 6); and compact buildings are warmer than open buildings (LCZ 1–3 > LST 4–6) in summer of China. That shows both mid-rise and compact buildings are not beneficial to cool urban. In addition, LST variations at daytime and in summer are more significant than nighttime and other seasons. (3) LST differences within LCZs are significant at p < 0.05, and are most significant in Jing-Jin-Ji (JJJ). The LST difference within built types (LCZ 1–10) is more significant than within natural types (LCZ A–G), showing that built types alteration will be more effective for thermal environmental improvement. (4) Under the current population and urban area, increasing greenness and water area in compact high-rise buildings are the most effective strategies for urban cooling in all three urban agglomerations, with the largest reduction in LST of 4.11 K in JJJ. These findings will provide support for thermal environment mitigation, urban planning and sustainable urban development.

Impact of different heat wave definitions on daily mortality in Bandafassi, Senegal

Objective

The aim of this study is to find the most suitable heat wave definition among 15 different ones and to evaluate its impact on total, age-, and gender-specific mortality for Bandafassi, Senegal.

Methods

Daily weather station data were obtained from Kedougou situated at 17 km from Bandafassi from 1973 to 2012. Poisson generalized additive model (GAM) and distributed lag non-linear model (DLNM) are used to investigate the effect of heat wave on mortality and to evaluate the nonlinear association of heat wave definitions at different lag days, respectively.

Results

Heat wave definitions, based on three or more consecutive days with both daily minimum and maximum temperatures greater than the 90^th percentile, provided the best model fit. A statistically significant increase in the relative risk (RRs 1.4 (95% Confidence Interval (CI): 1.2–1.6), 1.7 (95% CI: 1.5–1.9), 1.21 (95% CI: 1.08–1.3), 1.2 (95% CI: 1.04–1.5), 1.5 (95% CI: 1.3–1.8), 1.4 (95% CI: 1.2–1.5), 1.5 (95% CI: 1.07–1.6), and 1.5 (95% CI: 1.3–1.8)) of total mortality was observed for eight definitions. By using the definition based on the 90^th percentile of minimum and maximum temperature with a 3-day duration, we also found that females and people aged ≥ 55 years old were at higher risks than males and other different age groups to heat wave related mortality.

Conclusion

The impact of heat waves was associated with total-, age-, gender-mortality. These results are expected to be useful for decision makers who conceive of public health policies in Senegal and elsewhere. Climate parameters, including temperatures and humidity, could be used to forecast heat wave risks as an early warning system in the area where we conduct this research. More broadly, our findings should be highly beneficial to climate services, researchers, clinicians, end-users and decision-makers.

Association between extreme heat and hospital admissions for cataract patients in Hefei, China

Cataract is the first cause of blindness and the major cause of visual impairment worldwide. Under conditions of global warming, researchers have begun to give attention to the influence of increasing temperature on cataract patients. Our paper aimed to investigate the association between extreme heat and hospital admissions for cataract in Hefei, China. Based on data from the New Rural Cooperative Medical System and National Meteorological Information Center, we used a generalized additive model and a distributed lag nonlinear model to examine the relationship between extreme heat and hospitalizations for cataract, with consideration of cumulative and lagged effects. When current mean temperature was above 28 °C, each 1 °C rise was associated with a 4% decrease in the number of cataract admissions (RR = 0.96, 95% CI = 0.94-0.98). The cumulative relative risk over 11 days of lag was the lowest, which indicated that every 1 °C increase in mean temperature above 28 °C was associated with a 19% decrease in the number of hospital admissions for cataract (RR = 0.81, 95% CI = 0.75-0.88). In subgroup analyses, the negative association between extreme heat and hospital admissions for cataract was stronger among patients who were not admitted to provincial-level hospitals. In conclusion, this paper found that extreme heat was negatively associated with cataract hospitalizations in Hefei, providing useful information for hospitals and policymakers.

Transcriptome Analysis of Ophraella communa Male Reproductive Tract in Indirect Response to Elevated CO2 and Heat Wave

Increase in atmospheric CO₂ directly affects the insect physiology and behavior, and indirectly affects the herbivorous insects by affecting their hosts. The increase in atmospheric CO₂ is accompanied by an increase in temperature and heat waves. Ophraella communa LeSage is a natural enemy of Ambrosia artemisiifolia (common ragweed). The development and reproduction of this beetle is weakened upon eating common ragweed grown under stress conditions. As female behavior and physiology alter after mating, the reproductive tract of males is likely to modulate reproduction and development in this species. Herein, the transcriptional profiles of testes and accessory glands from male O. communa individuals feeding on common ragweed under conditions of high CO₂ concentration and heat waves and that grown under ambient CO₂ concentration were compared. Differentially expressed genes (DEGs) were identified between the same tissues from beetles fed on common ragweed grown under different stress conditions. There were 3, 2, 3, 1and 5 genes related to decomposition and transport of macromolecular substances, host location, stress response, reproduction, and poisonous food-utilization. No expected response was observed in the male reproductive tract, but some of the identified DEGs might control the development of the population. The results presented here should be helpful in guiding future studies on deciphering the indirect response of other organs to high CO₂ concentration and heat waves, as well as the functions of seminal fluid proteins in O. communa.

At which temperature do the deleterious effects of ambient heat "kick-in" to affect all-cause mortality? An exploration of this threshold from an eastern Indian city

Despite experiencing hot weathers, limited studies from India explored relationships between ambient heat and health. We studied associations between heat and all-cause mortality to estimate heat threshold(s) affecting health, and examine other affecting dimensions. We conducted time-series analysis with daily maximum temperature and all-cause mortality data of Bhubaneswar city (March-July, 2007-2017), and explored their interactions. Mortality risks rose when daily maximum temperatures were >36.2°C (lower threshold), and even more when >40.5°C (upper threshold). Every degree above36.2°C increased the mortality risk by 2% (mortality rate ratio: 1.02; 95% CI 1.01, 1.03). The effects of maximum temperature increased on days when minimum temperatures were >25.6°C (median). The effect of heat was immediate and lasted for 0-1 day with no lagged effect. Two temperature thresholds with varying mortality risks provided an opportunity for a graded heat warning system. The accentuation of the deleterious effects of heat by the higher minimum temperature calls for its inclusion in the heat warning system in future.

Performance of Different Urban Design Parameters in Improving Outdoor Thermal Comfort and Health in a Pedestrianized Zone

Global climate change and urban heat islands have generated heat stress in summer, which does harm to people’s health. The outdoor public commercial pedestrianized zone has an important role in people’s daily lives, and the utilization of this space is evaluated by their outdoor thermal comfort and health. Using microclimatic monitoring and numerical simulation in a commercial pedestrianized zone in Tai Zhou, China, this study investigates people’s outdoor thermal comfort in extreme summer heat. The final results provide a comprehensive system for assessing how to improve outdoor human thermal health. Under the guidance of this system, local managers can select the most effective strategy to improve the outdoor thermal environment.

Heat wave intensity and daily mortality in four of the largest cities of Spain

In the current context of climate change, heat waves have become a significant problem for human health. This study assesses the effects of heat wave intensity on mortality (natural, respiratory and cardiovascular causes) in four of the largest cities of Spain (Barcelona, Bilbao, Madrid and Seville) during the period between 1990 and 2014. To model the heat wave severity the Excess Heat Factor (EHF) was used. The EHF is a two-component index. The first is the comparison of the three-day average daily mean temperature with the 95th percentile. The second component is a measure of the temperatures reached during the three-day period compared with the recent past (the previous 30 days). The city-specific exposure-response curves showed a non-linear J-shaped relationship between mortality and the EHF. Overall city-specific mortality risk estimates in natural causes for 1st vs. 99th percentile increases range from the highest mortality risk with 2.73 (95% CI: 2.34-3.18) in Seville to a risk of 1.78 (95% CI: 1.62-1.97) and 1.78 (95% CI: 1.45-2.19) in Barcelona and Bilbao, respectively. When we compare our results with risk estimates for the analyzed Spanish cities in other studies, the heat wave related mortality risks seem to be clearly higher. Furthermore, it has been demonstrated that different heat wave days of the same event do not present the same degree of severity/intensity. Thus, the intensity of a heat wave is an important mortality risk indicator during heat wave days. Due to the low number of studies on the EHF as a heat wave intensity indicator and heat-related mortality and morbidity, further research is required to validate its application in other geographic areas and focus populations.

Using web data to improve surveillance for heat sensitive health outcomes

BACKGROUND

Elevated and prolonged exposure to extreme heat is an important cause of excess summertime mortality and morbidity. To protect people from health threats, some governments are currently operating syndromic surveillance systems. However, A lack of resources to support time- and labor- intensive diagnostic and reporting processes make it difficult establishing region-specific surveillance systems. Big data created by social media and web search may improve upon the current syndromic surveillance systems by directly capturing people's individual and subjective thoughts and feelings during heat waves. This study aims to investigate the relationship between heat-related web searches, social media messages, and heat-related health outcomes.

METHODS

We collected Twitter messages that mentioned "air conditioning (AC)" and "heat" and Google search data that included weather, medical, recreational, and adaptation information from May 7 to November 3, 2014, focusing on the state of Florida, U.S. We separately associated web data against two different sources of health outcomes (emergency department (ED) and hospital admissions) and five disease categories (cardiovascular disease, dehydration, heat-related illness, renal disease, and respiratory disease). Seasonal and subseasonal temporal cycles were controlled using autoregressive moving average-generalized autoregressive conditional heteroscedasticity (ARMA-GARCH) and generalized linear model (GLM).

RESULTS

The results show that the number of heat-related illness and dehydration cases exhibited a significant positive relationship with web data. Specifically, heat-related illness cases showed positive associations with messages (heat, AC) and web searches (drink, heat stroke, park, swim, and tired). In addition, terms such as park, pool, swim, and water tended to show a consistent positive relationship with dehydration cases. However, we found inconsistent relationships between renal illness and web data. Web data also did not improve the models for cardiovascular and respiratory illness cases.

CONCLUSIONS

Our findings suggest web data created by social medias and search engines could improve the current syndromic surveillance systems. In particular, heat-related illness and dehydration cases were positively related with web data. This paper also shows that activity patterns for reducing heat stress are associated with several health outcomes. Based on the results, we believe web data could benefit both regions without the systems and persistently hot and humid climates where excess heat early warning systems may be less effective.

Potential effects of heat waves on the population dynamics of the dengue mosquito Aedes albopictus

Extreme weather events affect the development and survival of disease pathogens and vectors. Our aim was to investigate the potential effects of heat waves on the population dynamics of Asian tiger mosquito (Aedes albopictus), which is a major vector of dengue and Zika viruses. We modeled the population abundance of blood-fed mosquito adults based on a mechanistic population model of Ae. albopictus with the consideration of diapause. Using simulated heat wave events derived from a 35-year historical dataset, we assessed how the mosquito population responded to different heat wave characteristics, including the onset day, duration, and the average temperature. Two important observations are made: (1) a heat wave event facilitates the population growth in the early development phase but tends to have an overall inhibitive effect; and (2) two primary factors affecting the development are the unusual onset time of a heat wave and a relatively high temperature over an extended period. We also performed a sensitivity analysis using different heat wave definitions, justifying the robustness of the findings. The study suggests that particular attention should be paid to future heat wave events with an abnormal onset time or a lasting high temperature in order to develop effective strategies to prevent and control Ae. albopictus-borne diseases.

Understanding the population dynamics of Asian Tiger mosquito (Ae. albopictus)–the most prevalent vector of global epidemics including West Nile virus, dengue fever, Zika–could shed lights on improving the understanding of vector transmission as well as developing effective disease control strategies. It is widely acknowledged that the life cycle of Ae. albopictus is firmly regulated by meteorological factors in a non-linear way and is sensitive to climate change. Our study extends the understanding about how extreme heat events manipulate the mosquito population abundance. We adopted an existing mechanistic population model of Ae. albopictus, combined with a rich set of simulated heat wave events derived from a 35-year historical dataset, to quantify the mosquito’s responses to different heat wave characteristics. We found that an abnormal onset time and a lasting high temperature play the most important role in affecting the mosquito population dynamics. We also performed a sensitive analysis by changing the definition of the heat wave, justifying the rigor of the conclusion. This research provides implications for developing public health intervention strategies: to control dengue fever, Zika, as well as other far-reaching mosquito-borne epidemics, priority should be given to heat wave events with an abnormal onset time or a lasting high temperature.

Heatwaves and hospitalizations due to hyperthermia in defined climate regions in the conterminous USA

Heatwaves are one of the deadliest natural disasters that occur annually with thousands of people seeking medical attention. The spatio-temporal synchronization between peaks in disease manifestation and high temperature provides important insights into the seasonal timing of the heatwave and the response it may cause with respect to emergence, severity, and duration. The objectives of this study are to examine the association between hospitalizations due to heat stroke in older adults and heat in the United States (US) and explore synchronization with respect to heatwave sequence, time of arrival, and regional climate. Three large data sets were utilized: daily hospitalization records of the US elderly between 1991 and 2006, annual demographic summaries on Medicare beneficiaries maintained by the Centers for Medicare and Medicaid Services (CMS), and nationwide daily meteorological observations. We modeled seasonal fluctuations in health outcomes, such as the timing and intensity of the seasonal peak in hospitalizations using refined harmonic GLM for eight climatically similar regions. During the 16-year study period, there were 40,019 heat-related hospitalizations (HRH) in the conterminous  US. The rates of HRH varied substantially across eight climatic regions: with the highest rate of 7.05 cases per million residents observed in areas with temperate arid summers and winters (TaTa) and the lowest rate of 0.67-in areas with cold moderately dry summers and arid winters (CdCa), where summer temperatures are about  18.3 °C and 12.1 °C, respectively. We detected 400 heatwaves defined as any day when the night time temperature is above its 90th percentile for the current and previous nights. The first seasonal heatwave in a season resulted in 4274 hospitalizations over 342 heatwave-days: 34.3% of 12,442 hospitalizations occurred in 26% of 1308 heatwave-days. The relative risks of increased HRH associated with the first and second heatwaves were 10.4 (95%CI: 8.5; 12.3) and 11.4 (95%CI: 9.6; 13.3), respectively, indicating the disproportional effects of early heatwave arrivals. The seasonal spike in heat stroke hospitalizations in regions with relatively similar annual temperatures, e.g. in areas with temperate moderately dry summers and winters (TdTa: 12.8 °C) and (TaTa: 11.1 °C) ranged between 4.5 (95%CI: 3.3; 5.5) and 11.0 (95%CI: 8.2; 14.9) cases per million residents, respectively, indicating substantial regional differences. The differences in heat-related hospitalizations and response to heatwaves are substantial among older adults residing in different climate regions of the conterminous US. The disproportionally high response to the early seasonal heatwave deserves special attention, especially in the context of prevention and decision support frameworks.

Health impact of climate change in cities of middle-income countries: the case of China

BACKGROUND

This review examines the human health impact of climate change in China. Through reviewing available research findings under four major climate change phenomena, namely extreme temperature, altered rainfall pattern, rise of sea level and extreme weather events, relevant implications for other middle-income population with similar contexts will be synthesized.

SOURCES OF DATA

Sources of data included bilingual peer-reviewed articles published between 2000 and 2018 in PubMed, Google Scholar and China Academic Journals Full-text Database.

AREAS OF AGREEMENT

The impact of temperature on mortality outcomes was the most extensively studied, with the strongest cause-specific mortality risks between temperature and cardiovascular and respiratory mortality. The geographical focuses of the studies indicated variations in health risks and impacts of different climate change phenomena across the country.

AREAS OF CONTROVERSY

While rainfall-related studies predominantly focus on its impact on infectious and vector-borne diseases, consistent associations were not often found.

GROWING POINTS

Mental health outcomes of climate change had been gaining increasing attention, particularly in the context of extreme weather events. The number of projection studies on the long-term impact had been growing.

AREAS TIMELY FOR DEVELOPING RESEARCH

The lack of studies on the health implications of rising sea levels and on comorbidity and injury outcomes warrants immediate attention. Evidence is needed to understand health impacts on vulnerable populations living in growing urbanized cities and urban enclaves, in particular migrant workers. Location-specific climate-health outcome thresholds (such as temperature-mortality threshold) will be needed to support evidence-based clinical management plans and health impact mitigation strategies to protect vulnerable communities.

Crisis support-seeking behavior and temperature in the United States: Is there an association in young adults and adolescents?

BACKGROUND

Mounting evidence demonstrates the relationship between high temperatures and adverse mental health outcomes. Yet, no study has examined the influence of temperature on crisis support-seeking behavior among youth in large urban areas.

METHODS

Crisis Text Line (CTL) is a text messaging service that provides crisis interventions for support-seeking individuals for a range of mental-health outcomes in the United States. We applied a distributed lag non-linear modeling technique to assess the short-term impacts of daily maximum and minimum temperature on crisis-related events in four metropolitan locations in the USA.

RESULTS

There were multiple positive associations in three of the four study locations that demonstrate crisis help-seeking behavior increased during anomalously warm conditions.

CONCLUSIONS

This study suggests that there is a significant association between high minimum or maximum temperatures and crisis help-seeking behaviors in young adults and adolescents in urban areas in the United States.

Analysis of Mortality Change Rate from Temperature in Summer by Age, Occupation, Household Type, and Chronic Diseases in 229 Korean Municipalities from 2007⁻2016

This study analyzed mortality change rate (MCR: daily change rate of mortality at a given temperature per average summer mortality) for 229 municipalities in Korea considering age, occupation, household type, chronic diseases, and regional temperature distribution. We found that the MCR for heat wave differs depending on socioeconomic factors and the temperature distribution in the region. The MCRs for the elderly (≥65 years of age), outdoor workers, one-person households, and chronic disease patients start to increase at lower temperatures and react more sensitively to temperature than others. For the socioeconomic factors considered in this study, occupation was found to be the most significant factor for the MCR differences (outdoor workers 1.17 and others 1.10 above 35 °C, p < 0.01). The MCRs of elderly outdoor workers increased consistently with temperature, while the MCRs of younger outdoor workers decreased at 33 °C, the heat wave warning level in Korea. The MCRs in lower temperature regions start to increase at 28 °C, whereas the MCRs start to increase at 30 °C in higher temperature regions. The results of this study suggest that heat wave policies should be based on contextualized impacts considering age, occupation, household type, chronic disease, and regional temperature distribution.

Impact of summer heat on mortality and years of life lost: Application of a novel indicator of daily excess hourly heat

BACKGROUND

Previous studies have widely assessed heat-mortality relationships across global regions, while the epidemiological evidence regarding the heat effect on years of life lost (YLL) is relatively sparse. Current investigations using daily mean data cannot take hourly temperature variation into consideration and may underestimate heat effects. We developed a novel indicator, daily excess hourly heat (DEHH), to precisely evaluate the potential heat effects on mortality and YLL.

METHODS

Hourly data on temperature and daily information, including concentrations of air pollutants, relative humidity, and records of all registered deaths were obtained in Wuhan, China during the warm seasons (May-September) of 2009-2012. DEHH, developed in this study, is defined as daily total hourly temperatures that exceed a specific heat threshold. By performing time series regression analyses, we assessed the changes in daily mortality and YLL per interquartile range (IQR) increase in DEHH across different lag days.

RESULTS

The heat threshold evaluated by the Akaike Information Criterion for DEHH calculation is 30 °C (92th percentile of whole-year mean temperature distribution). Daily average DEHH was 13.9 °C, with an IQR of 19.9 °C. Linear exposure-response curves were found between DEHH and two health outcomes. Generally, heat effects lasted for 2-3 days and DEHH at lag 0-1 was most strongly associated with increased mortality and YLL. The effects were especially remarkable for stroke and ischemic heart disease mortality. Most intense effect on YLL was found in non-accidental deaths (20.11, 95% confidence interval: 8.90-31.33) at lag 0-1. More DEHH-related mortality and YLL from cardiovascular deaths were observed among males. People aged 0-74 years and males suffered more from YLL burden due to high temperatures.

CONCLUSIONS

Our study demonstrated that DEHH may be an alternative indicator to precisely measure heat effects on daily mortality and YLL. Further DEHH-based evidence from large scale investigations is needed so as to better understand heat-associated health burden and improve public response to extremely high temperatures.

Impact of heat on mortality and morbidity in low and middle income countries: A review of the epidemiological evidence and considerations for future research

Heat waves and high air temperature are associated with increased morbidity and mortality. However, the majority of research conducted on this topic is focused on high income areas of the world. Although heat waves have the most severe impacts on vulnerable populations, relatively few studies have studied their impacts in low and middle income countries (LMICs). The aim of this paper is to review the existing evidence in the literature on the impact of heat on human health in LMICs. We identified peer-reviewed epidemiologic studies published in English between January 1980 and August 2018 investigating potential associations between high ambient temperature or heat waves and mortality or morbidity. We selected studies according to the following criteria: quantitative studies that used primary and/or secondary data and report effect estimates where ambient temperature or heat waves are the main exposure of interest in relation to human morbidity or mortality within LMICs. Of the total 146 studies selected, eighty-two were conducted in China, nine in other countries of East Asia and the Pacific, twelve in South Asia, ten in Sub-Saharan Africa, eight in the Middle East and North Africa, and seven in each of Latin America and Europe. The majority of studies (92.9%) found positive associations between heat and human morbidity/mortality. Additionally, while outcome variables and study design differed greatly, most utilized a time-series study design and examined overall heath related morbidity/mortality impacts in an entire population, although it is notable that the selected studies generally found that the elderly, women, and individuals within the low socioeconomic brackets were the most vulnerable to the effects of high temperature. By highlighting the existing evidence on the impact of extreme heat on health in LMICs, we hope to determine data needs and help direct future studies in addressing this knowledge gap. The focus on LMICs is justified by the lack of studies and data studying the health burden of higher temperatures in these regions even though LMICs have a lower capacity to adapt to high temperatures and thus an increased risk.

Extreme temperature and mortality: evidence from China

The frequency, intensity, and duration of extreme temperature events are expected to rise in the future and increase the related health risks of human beings. Using a novel, nationwide dataset that links extreme temperature and mortality, we estimated the short-term and long-term effects of extreme temperature on mortality in China during 2002-2013. Both extreme hot and extreme cold had immediate and long-term effects on all-cause mortality. Annual deaths per 100,000 people due to extreme hot and cold in the long term were considerably larger compared to the short term. The change in cold spell duration indicator exhibited the greatest effects on annual deaths per 100,000 people among a set of extreme weather indicators. Furthermore, cities with low economic development levels were more vulnerable to extreme temperature, compared to cities with high economic development levels. Our results offer important policy implications for developing a regional-specific extreme weather plan to handle extreme temperature events in China.

GHWR, a multi-method global heatwave and warm-spell record and toolbox

Heatwaves are extended periods of unusually high temperatures with significant societal and environmental impacts. Despite their significance, there is not a generalized definition for heatwaves. In this paper, we introduce a multi-method global heatwave and warm-spell data record and analysis toolbox (named GHWR). In addition to a comprehensive long-term global data record of heatwaves, GHWR allows processing and extracting heatwave records for any location efficiently. We use traditional constant temperature threshold methods, as well as spatially and temporally localized threshold approaches to identify heatwaves. GHWR includes binary (0/1) occurrence records of heatwaves/warm-spells, and annual summary files with detailed information on their frequency, duration, magnitude and amplitude. GHWR also introduces the standardized heat index (SHI) as a generalized statistical metric to identify heatwave/warm-spells. SHI has direct association with the probability distribution function of long-term daily temperatures for any given calendar day and spatial grid. Finally, GHWR offers a unique opportunity for users to select the type of heatwave/warm-spell information from a plethora of methods based on their needs and applications.

Mortality effects of heat waves vary by age and area: a multi-area study in China

BACKGROUND

Many studies have reported an increased mortality risk from heat waves comparing with non-heat wave days. However, how much the mortality rate change with the heat intensity-vulnerability curve-is still unknown. Such unknown information makes the related managers impossible to assess scientifically life losses from heat waves, consequently fail in conducting suitable integrated risk management measures.

METHODS

We used the heat wave intensity index (HWII) to characterize quantitatively the heat waves, then applied a distributed lag non-linear model to explore the area-specific definition of heat wave, and developed the vulnerability models on the relationships between HWII and mortality by age and by area. Finally, Monte Carlo method was run to assess and compare the event-based probabilistic heat wave risk during the periods of 1971-2015 and 2051-2095.

RESULTS

We found a localized definition of heat wave for each corresponding area based on the minimum AIC (Akaike information criterion). Under the local heat wave events, the expected life loss during 1971-2015 does distinguish across areas, and decreases consistently in the order of WZ Chongqing, PK Nanjing and YX Guangzhou for each age group. More specifically, for the elders (≥65), the average annual loss (AAL) (and 95% confidence interval) would be 61.3 (30.6-91.9), 38 (3.8-72.2) and 18.7 (7.3-30) deaths per million people. With two stresses from warming and aging in future China, the predicted average AAL of the elders under four Representative Carbon Pathways (2.6, 4.5, 6.0, and 8.5) during 2051-2095 would be 2460, 1675, 465 deaths per million for PK Nanjing, YX Guangzhou and WZ Chongqing, respectively, approximately becoming 8~ 90 times of the AAL during 1971-2015.

CONCLUSION

This study found that the non-linear HWII-mortality relationships vary by age and area. The heat wave mortality losses are closely associated with the social-economic level. With the increasing extreme climatic events and a rapid aging trend in China, our findings can provide guidance for policy-makers to take appropriate regional adaptive measures to reduce health risks in China.

Projecting future climate change impacts on heat-related mortality in large urban areas in China

Global climate change is anticipated to raise overall temperatures and has the potential to increase future mortality attributable to heat. Urban areas are particularly vulnerable to heat because of high concentrations of susceptible people. As the world's largest developing country, China has experienced noticeable changes in climate, partially evidenced by frequent occurrence of extreme heat in urban areas, which could expose millions of residents to summer heat stress that may result in increased health risk, including mortality. While there is a growing literature on future impacts of extreme temperatures on public health, projecting changes in future health outcomes associated with climate warming remains challenging and underexplored, particularly in developing countries. This is an exploratory study aimed at projecting future heat-related mortality risk in major urban areas in China. We focus on the 51 largest Chinese cities that include about one third of the total population in China, and project the potential changes in heat-related mortality based on 19 different global-scale climate models and three Representative Concentration Pathways (RCPs). City-specific risk estimates for high temperature and all-cause mortality were used to estimate annual heat-related mortality over two future twenty-year time periods. We estimated that for the 20-year period in Mid-21st century (2041-2060) relative to 1970-2000, incidence of excess heat-related mortality in the 51 cities to be approximately 37,800 (95% CI: 31,300-43,500), 31,700 (95% CI: 26,200-36,600) and 25,800 (95% CI: 21,300-29,800) deaths per year under RCP8.5, RCP4.5 and RCP2.6, respectively. Slowing climate change through the most stringent emission control scenario RCP2.6, relative to RCP8.5, was estimated to avoid 12,900 (95% CI: 10,800-14,800) deaths per year in the 51 cities in the 2050s, and 35,100 (95% CI: 29,200-40,100) deaths per year in the 2070s. The highest mortality risk is primarily in cities located in the North, East and Central regions of China. Population adaptation to heat is likely to reduce excess heat mortality, but the extent of adaptation is still unclear. Future heat mortality risk attributable to exposure to elevated warm season temperature is likely to be considerable in China's urban centers, with substantial geographic variations. Climate mitigation and heat risk management are needed to reduce such risk and produce substantial public health benefits.

The temperature-mortality relationship: an analysis from 31 Chinese provincial capital cities

We aim to explore the Minimum Mortality Temperature (MMT) of different cities and regions, and that provides evidence for developing reasonable heat wave definition in China. The death data of 31 Chinese provincial capital cities from seven geographical regions during 2008-2013 was included in this study. In the first stage, a DLNM (Distributed Lag Non-linear Model) was used to estimate the association between mean temperature and mortality in a single city, then we pooled them with a multivariate meta-analysis to estimate the region-specific effects. The range of MMT was from 17.4 °C (Shijiazhuang) to 28.4 °C (Haikou), and the regional MMT increased as the original latitude decreased. Different cities and regions have their own specialized MMT due to geography and demographic characteristics. These findings indicate that the government deserves to adjust measures to local conditions to develop public health policies.

China's adaptation to climate & urban climatic changes: A critical review

Since the conclusion of the 2014 Climate Summit in New York and the 21st Conference of the Parties (COP21) in Paris, China has been actively advancing its national policies on climate change mitigation and adaptation since more unpredictable extreme weather events are expected, which may incur a heavy cost in terms of economics and public health. Since China is still in the process of urbanisation, the greatest challenge it faces is finding a balance between economic growth and keeping carbon dioxide and greenhouse gas emission rates at a manageable level. Cities in China play a key role in the implementation of the central policies and make concrete actions in response to climate change. With reference to a series of recent policy papers and action plans as the background, this paper attempts to provide a critical overview of China's climate change action plans from the national to the city and urban level. It seeks to understand whether the proposed responses to climate change and strategies for actions on greening and air corridors for cities and urban areas are appropriate. It is found that for China to advance its urban climatic adaptation strategy there is a need for (1) urban data, (2) a cross-disciplinary impact assessment, and (3) the development of a market and policy transformation mechanism.

Different response of human mortality to extreme temperatures (MoET) between rural and urban areas: A multi-scale study across China

BACKGROUND

The environmental variation in mortality due to extreme temperatures has been well-documented by many studies. Mortality to extreme temperatures (MoET) was recognized to vary geographically, either by countries within a region or by areas within a country. However, so far, little attention has been paid to rural residents, with even lesser attention on the potential rural-urban differences. The aim of our study was to offer a quite comprehensive analysis on the differences in temperature-mortality relationship between rural and urban areas across China.

METHOD

A distributed lag nonlinear model was built to describe the temperature-mortality relationship, based on the mortality data and meteorological variable of 75 communities in China from 2007 to 2012. Subsequently, a meta-analysis was applied to compare the differences in the temperature-mortality relationship between rural and urban areas at various levels.

RESULTS

Distinct responses regarding MoET between rural and urban areas were observed at different spatial scales. At regional level, more U-shaped curves were observed for temperature-mortality relationships in urban areas, while more J-shaped curves were observed in rural areas. At national scale, we found that the cold effect was stronger in rural areas (RR: rural 1.69 vs. urban 1.51), while heat effect was stronger in urban areas (RR: rural 1.01 vs. urban 1.12). Moreover, the modifying influence of air pollution on temperature-mortality relationship was found to be very limited.

CONCLUSION

The difference in response of MoET between rural and urban areas was noticeable, cold effect is more significant in China both in rural and urban areas. Additionally, urban areas in southern China and rural areas in northern China suffered more from extreme temperature events. Our findings suggest that differences in rural-urban responses to MoET should be taken seriously when intervention measures for reducing the risks to residents' health were adopted.

Projecting temperature-related years of life lost under different climate change scenarios in one temperate megacity, China

Temperature has been associated with population health, but few studies have projected the future temperature-related years of life lost attributable to climate change. To project future temperature-related disease burden in Tianjin, we selected years of life lost (YLL) as the dependent variable to explore YLL attributable to climate change. A generalized linear model (GLM) and distributed lag non-linear model were combined to assess the non-linear and delayed effects of temperature on the YLL of non-accidental mortality. Then, we calculated the YLL changes attributable to future climate scenarios in 2055 and 2090. The relationships of daily mean temperature with the YLL of non-accident mortality were basically U-shaped. Both the daily mean temperature increase on high-temperature days and its drop on low-temperature days caused an increase of YLL and non-accidental deaths. The temperature-related YLL will worsen if future climate change exceeds 2 °C. In addition, the adverse effects of extreme temperature on YLL occurred more quickly than that of the overall temperature. The impact of low temperature was greater than that of high temperature. Men were vulnerable to high temperature compared with women. This analysis highlights that the government should formulate environmental policies to reach the Paris Agreement goal.

Innovative urban forestry governance in Melbourne?: Investigating "green placemaking" as a nature-based solution

A nature-based approach to climate resilience aims to challenge and re-frame conventional environmental management methods by refocusing solutions from technological strategies to socio-ecological principles such as human well-being and community-based governance models, thereby improving and legitimizing the delivery of ecosystem services (ES). There are, however, many challenges to applying a socio-ecological agenda to urban climate resilience and thereby re-framing ES delivery as community and people focused, a knowledge gap extensively outlined in the environmental governance literature. In this paper, we aim to contribute to this re-assesment of urban environmental governance by examining the City of Melbourne's approach to urban re-naturing governance from a place-based perspective. Here we focus on the city's internationally-acclaimed urban forest strategy (UFS), investigating how and to which extent the governance arrangements embedded within the UFS draw strength from diverse perspectives and allow for institutional arrangements that support "situated" reflexive decision making and co-creation. We find that Melbourne's UFS governance process fosters green placemaking by re-focusing climate adaptation solutions from technological strategies to situated socio-ecological principles such as human well-being and community-based decision making. In this sense, this case provides valuable insight for the broader UGI governance field regarding the opportunities and challenges associated with a socio-cultural approach to urban re-naturing and ES delivery.

Characterizing prolonged heat effects on mortality in a sub-tropical high-density city, Hong Kong

Extreme hot weather events are likely to increase under future climate change, and it is exacerbated in urban areas due to the complex urban settings. It causes excess mortality due to prolonged exposure to such extreme heat. However, there is lack of universal definition of prolonged heat or heat wave, which leads to inadequacies of associated risk preparedness. Previous studies focused on estimating temperature-mortality relationship based on temperature thresholds for assessing heat-related health risks but only several studies investigated the association between types of prolonged heat and excess mortality. However, most studies focused on one or a few isolated heat waves, which cannot demonstrate typical scenarios that population has experienced. In addition, there are limited studies on the difference between daytime and nighttime temperature, resulting in insufficiency to conclude the effect of prolonged heat. In sub-tropical high-density cities where prolonged heat is common in summer, it is important to obtain a comprehensive understanding of prolonged heat for a complete assessment of heat-related health risks. In this study, six types of prolonged heat were examined by using a time-stratified analysis. We found that more consecutive hot nights contribute to higher mortality risk while the number of consecutive hot days does not have significant association with excess mortality. For a day after five consecutive hot nights, there were 7.99% [7.64%, 8.35%], 7.74% [6.93%, 8.55%], and 8.14% [7.38%, 8.88%] increases in all-cause, cardiovascular, and respiratory mortality, respectively. Non-consecutive hot days or nights are also found to contribute to short-term mortality risk. For a 7-day-period with at least five non-consecutive hot days and nights, there was 15.61% [14.52%, 16.70%] increase in all-cause mortality at lag 0-1, but only -2.00% [-2.83%, -1.17%] at lag 2-3. Differences in the temperature-mortality relationship caused by hot days and hot nights imply the need to categorize prolonged heat for public health surveillance. Findings also contribute to potential improvement to existing heat-health warning system.

Current and Projected Burden of Disease From High Ambient Temperature in Korea

BACKGROUND

The objective of the present study was to estimate the current and projected burden of disease from high ambient temperature using population-based data sources of nationwide mortality and morbidity in Korea.

METHODS

Disability-adjusted life years (DALY) were estimated using noninjury-related deaths, and cerebrovascular and cardiovascular diseases from recently released nationwide health and mortality databases. Years of life lost and years lost due to disability were measured based on the point prevalence and number of deaths during the study period. Future DALY attributable to heat waves were estimated from projected populations, and temperature predictions for the years 2030 and 2050 were under Representative Concentration Pathways (RCP) 4.5 and 8.5 with summertime temperatures above threshold.

RESULTS

Relative risks (RR) of total mortality and of cardiovascular disease were 1.02 (95% CI, 1.01, 1.02) and 1.08 (95% CI, 1.06, 1.09) for each 1°C increase in temperature above threshold, respectively. The morbidity of heat-related disease was RR 1.67 (95% CI, 1.64, 1.68) for each 1°C increase in temperature above threshold. DALY for all-cause death were 0.49 DALY/1000 in 2011, 0.71 (0.71) DALY/1000 in 2030 and 0.77 (1.72) DALY/1000 in 2050 based on RCP 4.5 (RCP 8.5). DALY for cardio- and cerebrovascular diseases were 1.24 DALY/1000 in 2011, 1.63 (1.82) DALY/1000 in 2030, and 1.76 (3.66) DALY/1000 in 2050 based on RCP 4.5 (RCP 8.5).

CONCLUSIONS

Future excess mortality due to high ambient temperature is expected to be profound in Korea. Efforts to mitigate climate change can provide substantial health benefits via reducing heat-related mortality.

Nonlinear relationship between extreme temperature and mortality in different temperature zones: A systematic study of 122 communities across the mainland of China

BACKGROUND

Numerous previous studies have reported that human health risk is extremely sensitive to temperature. Very few studies, however, have characterized the relationship between temperature and mortality in different temperature zones due to the previous conclusions deduced from a regional or administrative division. A research covers different temperature zones was indispensable to have a comprehensive understanding of regional ambient temperature effect on public health.

METHODS

Based on the mortality dataset and meteorological variables of 122 communities in China from 2007 to 2012, a distributed lag nonlinear model (DLNM) was utilized to estimate the temperature effect on non-accidental mortality at the community level. Then, a meta-regression analysis was applied to pool the estimates of community-specific effects in various latitude-effected temperature zones.

RESULTS

At the community level, the mean value of relative extreme cold risk (1.63) of all 122 communities was higher than that of extreme high temperature (1.15). At regional level, we found temperature-mortality relationship (e.g., U- or J-shaped) varied in different temperature zones. Meanwhile, the minimum-mortality temperature of each zone was near the 75th percentile of local mean temperature except the north subtropics (50th percentiles). Lag effect was also obvious, especially for cold effect. An interesting M-shaped curve for the relationship between cold risk and temperature was detected, while an inverted "U" shaped with a right tail for the heat effect. Such different responses might be attributed to the difference in social-economic status of temperature zones.

CONCLUSION

The temperature-mortality relationship showed a distinct spatial heterogeneity along temperature zones across the Chinese mainland. Different characteristics of mortality responding to cold and heat stress highlighted the fact that, apart from the circumstance of temperature, the social-economic condition was also linked with health risk. Our findings suggest decision-makers should take more adaptive and effective measures to reduce health risks in China.

The impact of temperature extremes on mortality: a time-series study in Jinan, China

OBJECTIVE

To investigate the relationship between temperature extremes and daily number of deaths in Jinan, a temperate city in northern China.

METHODS

Data ondaily number of deaths and meteorological variables over the period of 2011-2014 were collected. Cold spells or heat waves were defined as ≥3 consecutive days with mean temperature ≤5th percentile or ≥95th percentile, respectively. We applied a time-series adjusted Poisson regression to assess the effects of extreme temperature on deaths.

RESULTS

There were 152 150 non-accidental deaths over the study period in Jinan, among which 87 607 people died of cardiovascular disease, 11 690 of respiratory disease, 33 001 of stroke and 6624 of chronic obstrutive pulmonary disease (COPD). Cold spells significantly increased the risk of deaths due to non-accidental mortality (RR 1.08, 95% CI 1.06 to 1.11), cardiovascular disease (RR 1.06, 95% CI 1.03 to 1.10), respiratory disease (RR 1.19, 95% CI 1.11 to 1.27), stroke (RR 1.11, 95% CI 1.06 to 1.17) and COPD (RR 1.27, 95% CI 1.16 to 1.38). Heat waves significantly increased the risk of deaths due to non-accidental mortality (RR 1.02, 95% CI 1.00 to 1.05), cardiovascular disease (RR 1.03, 95% CI 1.00 to 1.06) and stroke (RR 1.06, 95% CI 1.00 to 1.13). The elderly were more vulnerable during heat wave exposure; however, vulnerability to cold spell was the same for the whole population regardless of age and gender.

CONCLUSIONS

Both cold spells and heat waves have increased the risk of death in Jinan, China.

Does temperature modify the effect of PM10 on mortality? A systematic review and meta-analysis

Large and growing literature has explored whether temperature modified the effect of particular matter (PM) on mortality, but results of the modification effect are inconsistent. In this study, we reviewed information from 29 studies to get the qualitative evidence of the modification effects of temperature on PM to mortality, and the data from 16 of the 29 studies were extracted to conduct a meta-analysis. Temperatures were grouped into three level: "low", "middle" and "high" according to the original studies. The random effect model was used in the meta-analysis with the relative risk (RR) as the measure indicator. The RRs (95% confidence intervals, CIs) for non-accidental death, cardiovascular death and respiratory death per 10 μg/m³ increase in PM₁₀ were 1.004 (1.003, 1.006), 1.005 (1.003,1.007), and 1.005 (1.000,1.010) in the low temperature level, 1.005 (1.004,1.006), 1.005 (1.004,1.007), and 1.008 (1.006, 1.010) in the middle temperature level, and 1.012 (1.010, 1.015), 1.016 (1.010, 1.022) and 1.019 (1.010,1.028) in the high temperature level, respectively. In conclusion, moderate evidence exists that temperature modifies the effect of PM₁₀ on mortality. The effect of PM₁₀ on respiratory death was the greatest, while the effect on non-accidental death was the smallest in the same temperature level. In addition, the effects of PM₁₀ on all the three kinds of mortality were the biggest in the high-temperature level, and the smallest in the low-temperature level.

Global climate change: impact of heat waves under different definitions on daily mortality in Wuhan, China

Background

There was no consistent definition for heat wave worldwide, while a limited number of studies have compared the mortality effect of heat wave as defined differently. This paper aimed to provide epidemiological evidence for policy makers to determine the most appropriate definition for local heat wave warning systems.

Methods

We developed 45 heat wave definitions (HWs) combining temperature indicators and temperature thresholds with durations. We then assessed the impact of heat waves under various definitions on non-accidental mortality in hot season (May–September) in Wuhan, China during 2003–2010.

Results

Heat waves defined by HW14 (daily mean temperature ≥ 99.0th percentile and duration ≥ 3 days) had the best predictive ability in assessing the mortality effects of heat wave with the relative risk of 1.63 (95% CI: 1.43, 1.89) for total mortality. The group-specific mortality risk using official heat wave definition of Chinese Meteorological Administration was much smaller than that using HW14. We also found that women, and the elderly (age ≥ 65) were more susceptible to heat wave effects which were stronger and longer lasting.

Conclusion

These findings suggest that region specific heat wave definitions are crucial and necessary for developing efficient local heat warning systems and for providing evidence for policy makers to protect the vulnerable population.

Electronic supplementary material

The online version of this article (doi:10.1186/s41256-017-0030-2) contains supplementary material, which is available to authorized users.