Effect modifications of green space and blue space on heat-mortality association in Hong Kong, 2008-2017

Delayed effects of the relative humidity on the outpatient visits of dry eye disease in Shanghai, China: effect modification by green and blue space

Background

Few studies have examined the influence of relative humidity (RH) on dry eye disease (DED), particularly in the context of the urban environment. The objective of this study was to investigate the influence of RH on the frequency of outpatient visits for DED among patients residing in diverse urban settings.

Methods

Data pertaining to outpatient visits, together with data on the DED, meteorological factors and air pollutants in Shanghai for the period 2019-2023, were retrieved. To analyse the nonlinear connection and lag impact between RH and outpatient visits for DED patients, a distributed lag nonlinear model (DLNM) was fitted.

Results

A total of 159 832 cases were utilised for the investigation. The results of the single-day lag pattern demonstrated a significant correlation between elevated RH exposure and DED. Lower RH was a substantial risk factor for DED on the basis of the cumulative-day effect pattern. Male were more susceptible to DED, and patients aged 0-18 years presented more stable performance in response to RH influences. In the cumulative-day lag pattern, the green space groups, the RR of the >60 years subgroup was greater than that of the other subgroups, and in the blue space groups, the RR of the 19-60 subgroup of blue space low was higher than that of the blue space high.

Conclusions

Reduced RH increases the relative risk of DED outpatient visits and suggests that a specific disease burden is associated with low RH exposure. Additionally, green and blue spaces in urban areas influence RH, which in turn affects the outpatient visits of DED at different ages.

Estimating Heat-Related Mortality Burden Changes under Type-Specific Green and Blue Space Scenarios in China

BACKGROUND

Green and blue spaces (GBS) are assumed to mitigate heat-induced health risks. However, few studies have explored the impact of type-specific GBS changes on heat-related mortality burden.

OBJECTIVES

This study aimed to investigate the effect modifications of different GBS types on heat-related mortality risks, and to estimate the changes in mortality burden in multiple GBS scenarios.

METHODS

A case time-series study design was utilized based on the daily data on all-cause mortality and temperatures from 2009 to 2020 in 1,085 subdistricts in China. Mortality count data were obtained from the Zhejiang Center for Disease Control and Prevention. Meteorological data on temperature and relative humidity were acquired from the Zhejiang Meteorological Bureau. GBS exposure was assessed by integrating fine-scale population density, GBS boundary from Baidu and OpenStreetMap, and street-view image data from Baidu. Conditional Poisson regression analyses were conducted with the distributed lag nonlinear model, incorporating modifiers of type-specific GBS exposure. Changes in heat-attributable mortality under different GBS scenarios were also assessed.

RESULTS

Heat-related mortality risks were lower for populations with high exposure (95%) than for those with low exposure (5%) a) to overall green spaces, forests, parks, nature reserves, and street greenery, rather than to grasses, farms, and scrubs; and b) to overall blue spaces, lakes, and rivers, rather than reservoirs, wetlands, or coasts. Increases of 10%, 20%, and 30% exposure to overall green spaces are expected to avoid heat-related mortality burden by 1.6% [95% empirical confidence interval (eCI): 1.4, 1.9, 3.2% (95% eCI: 2.5, 3.9), and 4.8% (95% eCI: 3.5, 6.2)], respectively, whereas corresponding estimates for overall blue spaces are 5.4% (95% eCI: 4.4, 6.4), 10.8% (95% eCI: 8.5, 13.3), and 16.2% (95% eCI: 12.3, 20.5), respectively. Conversely, a 30% decrease in overall green space exposure and overall blue space exposure will increase the heat-related mortality burden by 4.8% (95% eCI: 4.3, 5.2) and 15.9% (95% eCI: 15.2, 16.7), respectively.

DISCUSSION

Our study revealed differences in the capacity of various GBS types to mitigate heat-related mortality risks. While the protective effects of GBS may be moderate, targeted planning strategies should prioritize their implementation for maximum benefits in mitigating heat-related health risks. The continuous shrinkage of the GBS would render other efforts futile, such as heat-health action plans. https://doi.org/10.1289/EHP14014.

The combined effects of sleep and extreme heat exposure on cognitive function among older adults

BACKGROUND

Extreme heat is linked to cognitive impairment. Normal sleep duration and good sleep quality can reduce cognitive impairment risks. However, the combined impact of sleep (duration and quality) and extreme heat on cognitive impairment is unclear. This study tests whether normal sleep duration and good sleep quality during a heatwave reduce cognitive impairment compared to poor sleep quality and long sleep duration in older adults.

METHODS

This study used cohort data from 9153 older adults. Extreme heat was defined as periods ≥ 3 days with daily minimum temperatures above the 92.5th percentile during the warm season. Cognitive function was assessed with the Mini-Mental State Examination (MMSE). Sleep duration was categorized as long, normal, or short, and sleep quality as good or poor. Six and four categories were used for combinations of heatwave exposure with sleep duration and quality, respectively. Cox regression models were applied for analysis.

RESULTS

Compared to those with long sleep duration during heatwaves, participants exposed to heatwaves with normal sleep duration had lower cognitive impairment risk (HR: 0.86, 95 %CI: 0.76-0.97). Those exposed to extreme heat with short sleep duration also showed lower cognitive risks (HR: 0.74, 95 %CI: 0.62-0.88). Compared to those with poor sleep quality during heatwave, participants with good sleep quality during heatwaves did not show significantly lower cognitive impairment risk (HR: 1.10, 95 %CI: 0.98-1.23).

CONCLUSION

Older adults with normal or short sleep duration during heatwaves may face lower cognitive impairment risks, highlighting the importance of sleep guidance to protect cognitive health during extreme heat.

Associations between blue space exposure and rheumatoid arthritis: The modifying effect of genetic susceptibility and air pollutants

Studies on the interaction among genetic susceptibility, blue space exposure, and rheumatoid arthritis (RA) risk have been lacking. Therefore, we examined the association between blue space exposure and RA incidence and assess the modifying effect of genetic susceptibility and air pollutants. Form the UK Biobank, 322,783 participants without RA were enrolled in this study. The association between blue space exposure and RA incidence was estimated using a cox proportional hazards model. The combined effect of blue space and genetic factors on the risk of RA was further evaluated. The polygenic risk score (PRS) for RA was calculated to represent individual genetic risk, and the potential modification effect of air pollution on the relationship between blue space, PRS, and RA were explored. During a median follow-up of 12.4 years, 3659 RA cases were identified. A 10 % increase in blue space300 m was associated with a 22.6 % reduction in RA incidence (HR=0.774, 95 % CI: 0.670, 0.895), exhibiting a consistent downward trend in the exposure-response curve. A high PRS was an independent risk factor for RA (HR=1.393, 95 % CI: 1.347, 1.439). The associations between blue space exposure, PRS, and the risk of RA were dose-dependent, with the lowest risk observed among those with high levels of blue space and lower PRS (HRbluespace300m=0.501, 95 % CI: 0.431, 0.583; HRbluespace1000m=0.476, 95 % CI: 0.408, 0.555). Interaction analysis indicated that increased concentrations of air pollutants strengthened the relationship between PRS and RA. Blue space exposure mitigated the risk of RA development, particularly in individuals with low genetic risk.

Health impact of urban green spaces: a systematic review of heat-related morbidity and mortality

OBJECTIVES

The objective of this review was to scrutinise the impact of urban green spaces on heat-related morbidity and mortality.

DESIGN

This systematic review was meticulously carried out following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines DATA SOURCES: A comprehensive search was conducted across PubMed, Scopus and Google Scholar including studies from January 2000 to December 2022.

ELIGIBILITY CRITERIA

Studies that examined the influence of urban green spaces on heat-related morbidity and mortality, including randomised controlled trials, observational and modelling studies, were included.

DATA EXTRACTION AND SYNTHESIS

A total of 3301 publications were initially identified, out of which 12 studies met the inclusion criteria and were selected for analysis. The selected studies were predominantly from high-income and upper-middle-income nations (95%).

RESULTS

The research points towards a pattern where regions abundant in green spaces report lower rates of heat-related morbidity and mortality in contrast to those with sparse greenery. Additionally, urban vegetation appears to exert a positive influence on mental health and well-being, potentially aiding in offsetting the adverse health repercussions of high temperatures.

CONCLUSION

Urban green spaces play a vital role in mitigating heat-related health risks, offering a potential strategy for urban planning to address climate change and enhance public health. Additional research is required to thoroughly comprehend the magnitude of urban greenery's impact on heat-related morbidity and mortality, as well as its interplay with other variables, including air pollution, socioeconomic status, among others.

Do greenspaces really reduce heat health impacts? Evidence for different vegetation types and distance-based greenspace exposure

BACKGROUND

While vegetation type, population density and proximity to greenspaces have been linked to human health, what type and location of greenspace matter most have remained unclear. In this context, there are question marks over investment-style metrics.

OBJECTIVES

This paper aims at establishing what vegetation type may matter most in modifying heat-mortality associations, and what the optimal buffer distances of total and specific types of greenspace exposure associated with reduced heat-related mortality risks are.

METHODS

We conducted small-area analyses using daily mortality data for 286 Territory Planning Units (TPUs) across Hong Kong and 1 × 1 km gridded air temperature data for the summer months (2005-2018). Using a case time series design, we examined effect modifications of total and specific types of greenspaces, as well as population-weighted exposure at varying buffer distances (200-4000 m). We tested the significance of effect modifications by comparing relative risks (RRs) between the lowest and highest quartiles of each greenspace exposure metric; and explored the strength of effect modifications by calculating the ratio of RRs.

RESULTS

Forests, unlike grasslands, showed significant effect modifications on heat-mortality associations, with RRs rising from 0.98 (95 %CI: 0.92,1.05) to 1.06 (1.03, 1.10) for the highest to lowest quartiles (p-value = 0.037) The optimal distances associated with the most apparent effects were around 1 km for population-weighted exposure, with the ratio of RRs being 1.424 (1.038,1.954) for NDVI, 1.191 (1.004,1.413) for total greenspace, and 1.227 (1.024,1.470) for forests. A marked difference was observed in terms of the paired area-level and optimal distance-based exposure to total greenspace and forests under extreme heat (p-values < 0.05).

DISCUSSION

Our findings suggest that greenspace, particularly nearby forests, may significantly mitigate heat-related mortality risks.

Modifying temperature-related cardiovascular mortality through green-blue space exposure

Green-blue spaces (GBS) are pivotal in mitigating thermal discomfort. However, their management lacks guidelines rooted in epidemiological evidence for specific planning and design. Here we show how various GBS types modify the link between non-optimal temperatures and cardiovascular mortality across different thermal extremes. We merged fine-scale population density and GBS data to create novel GBS exposure index. A case time series approach was employed to analyse temperature-cardiovascular mortality association and the effect modifications of type-specific GBSs across 1085 subdistricts in south-eastern China. Our findings indicate that both green and blue spaces may significantly reduce high-temperature-related cardiovascular mortality risks (e.g., for low (5%) vs. high (95%) level of overall green spaces at 99th vs. minimum mortality temperature (MMT), Ratio of relative risk (RRR) = 1.14 (95% CI: 1.07, 1.21); for overall blue spaces, RRR = 1.20 (95% CI: 1.12, 1.29)), while specific blue space types offer protection against cold temperatures (e.g., for the rivers at 1st vs MMT, RRR = 1.17 (95% CI: 1.07, 1.28)). Notably, forests, parks, nature reserves, street greenery, and lakes are linked with lower heat-related cardiovascular mortality, whereas rivers and coasts mitigate cold-related cardiovascular mortality. Blue spaces provide greater benefits than green spaces. The severity of temperature extremes further amplifies GBS's protective effects. This study enhances our understanding of how type-specific GBS influences health risks associated with non-optimal temperatures, offering valuable insights for integrating GBS into climate adaptation strategies for maximal health benefits.

Impacts of social deprivation on mortality and protective effects of greenness exposure in Hong Kong, 1999-2018: A spatiotemporal perspective

Addressing health inequality is crucial for fostering healthy city development. However, there is a dearth of literature simultaneously investigating the effects of social deprivation and greenness exposure on mortality risks, as well as how greenness exposure may mitigate the adverse effect of social deprivation on mortality risks from a spatiotemporal perspective. Drawing on socioeconomic, remote sensing, and mortality record data, this study presents spatiotemporal patterns of social deprivation, population weighted greenness exposure, and all-cause and cause-specific mortality in Hong Kong. A Bayesian regression model was applied to investigate the impacts of social deprivation and greenness exposure on mortality and examine how socioeconomic inequalities in mortality may vary across areas with different greenness levels in Hong Kong from 1999 to 2018. We observed a decline in social deprivation (0.67-0.56), and an increase in greenness exposure (0.34-0.41) in Hong Kong during 1999-2018. Areas with high mortality gradually clustered in the Kowloon Peninsula and the northern regions of Hong Kong Island. Adverse impacts of social deprivation on all-cause mortality weakened in recent years (RR from 2009 to 2013: 1.103, 95%CI: 1.051-1.159, RR from 2014 to 2018: 1.041 95%CI: 0.950-1.139), while the protective impacts of greenness exposure consistently strengthened (RR from 1999 to 2003: 0.903, 95%CI: 0.827-0.984, RR from 2014 to 2018: 0.859, 95%CI: 0.763-0.965). Moreover, the adverse effects of social deprivation on mortality risks were found to be higher in areas with lower greenness exposure. These findings provide evidence of associations between social deprivation, greenness exposure, and mortality risks in Hong Kong over the past decades, and highlight the potential of greenness exposure to mitigate health inequalities. Our study provides valuable implications for policymakers to develop a healthy city.

A nested case-control study of serum zinc and incident diabetes among Chinese adults: Effect modifications and mediation analysis

Although numerous evidences suggest that zinc may have a beneficial impact on preventing and treating diabetes, findings from the population studies are inconclusive. To address this gap, we conducted a nested case-control study, employing restricted cubic splines and a conditional logistic regression model to explore the association between serum zinc levels and the risk of diabetes. We also assessed potential effect modifications through stratified analyses and examined the mediating effects of metabolic indicators using a multiclass mediation effect model. We measured baseline serum zinc concentrations using Inductively Coupled Plasma Mass Spectrometry in a cohort of 2156 participants, including 1078 individuals with diabetes and 1078 matched controls. Our findings revealed a 51 % increased risk of diabetes when comparing the highest quartile (Q4) to the lowest quartile (Q1) of serum zinc levels (Odds Ratio [95 % Confidence Interval]: 1.51 [1.09, 2.09]). There was a positive linear dose-response relationship between serum zinc and diabetes risk (P overall ≤0.01, P nonlinear = 0.20). Effect modifications were evident between serum zinc and factors such as educational attainment, body mass index, alcohol index, family history of diabetes, history of hypertension, coronary heart disease, and stroke, all of which influenced the risk of diabetes (all P-interaction <0.05). Moreover, our study identified significant indirect effects of triglycerides levels on diabetes risk for participants in the third (Q3) and fourth (Q4) quartiles of serum zinc, with mediation proportions of 19.23 % and 19.28 %, respectively. A significant indirect effect of alanine aminotransferase on diabetes risk was found for those in the Q4 of serum zinc, with a mediation proportion of 12.05 %. Considering these findings, it is advisable to conduct testing for serum zinc level and exercise caution when considering zinc supplementation. Furthermore, our results emphasized the necessity for additional validation through large-sample prospective population studies and experimental research.

Heatwave exposure in relation to decreased sleep duration in older adults

Few studies have delved into the effects of heatwaves on sleep duration loss among older adults. Our study examined correlations between heatwave exposure and sleep duration reductions in this demographic. Utilizing data of 7,240 older adults drawn from the China Health and Retirement Longitudinal Study (CHARLS) from 2015 to 2018, we assessed sleep duration differences between the baseline year (2015) and follow-up year (2018). Absolute reductions in sleep duration were defined as differences of ≥ 1, 1.5, or 2 h. Changes in sleep duration were categorized based on cut-offs of 5 and 8 h, including excessive decrease, moderate to short and persistent short sleep duration types. 12 heatwave definitions combining four thresholds (90th, 92.5th, 95th, and 97.5th percentiles of daily minimum temperature) and three durations (≥2, ≥3 and ≥ 4 days) were used. Heatwave exposure was determined by the difference in the number of 12 preceding months' heatwave days or events in 2015 and the number of 12 preceding months' heatwave days or events in 2018. The results showed that increased heatwave events (defined as ≥ P90th percentile & lasting three days) were associated with a higher likelihood of ≥ 1-hour sleep reduction and persistent short sleep duration. An increase in heatwave event (defined as ≥ P95th percentile & lasting three days) was linked to shifts from moderate to short sleep duration. For the association between an absolute reduction in sleep duration and heatwave exposure, while higher thresholds signified greater sleep reduction risks, the effect estimates of longer durations were not uniformly consistent. We observed that air pollution and green space modified the relationship between heatwaves and sleep duration. Females, urban residents, and individuals with chronic diseases were identified as vulnerable populations. This study found that increased heatwave exposure was associated with a higher risk of sleep duration loss in older adults.

The effects of heatwave on cognitive impairment among older adults: Exploring the combined effects of air pollution and green space

The association between heatwaves and cognitive impairment in older adults, especially the joint effect of air pollution and green space on this association, remains unknown. The present cohort study used data from waves of the Chinese Longitudinal Healthy Longevity Survey (CLHLS) from 2008 to 2018. Heatwaves were defined as having daily maximum temperature ≥ 92.5th, 95th and 97.5th percentile that continued at least two, three and four days, measured as the one-year heatwave days prior to the participants' incident cognitive impairment. Data on the annual average air pollutant concentrations of fine particulate matter (PM2.5) and ozone (O3) as well as green space exposure (according to the Normalized Difference Vegetation Index (NDVI)) were collected. Time-varying Cox proportional hazards models were constructed to examine the independent effect of heatwaves on cognitive impairment and the combined effect of heatwaves, air pollution, and green space on cognitive impairment. Potential multiplicative interactions were examined by adding a product term of air pollutants and NDVI with heatwaves in the models. The relative excess risk due to interaction (RERI) was calculated to reflect additive interactions. We found that heatwave exposure was associated with higher risks of cognitive impairment, with hazard ratios (HRs) and 95 % confidence intervals (CIs) ranging from 1.035 (95 % CI: 1.016-1.055) to 1.058 (95 % CI: 1.040-1.075). We observed a positive interaction of PM2.5 concentrations, O3 concentrations, lack of green space, and heatwave exposure on a multiplicative scale (HRs for product terms >1). Furthermore, we found a synergistic interaction of PM2.5 concentrations, O3, lack of green space, and heatwave exposure on an additive scale, with RERIs >0. These results suggest that extreme heat exposure may be a potential risk factor for cognitive impairment in older adults. Additionally, coexposure to air pollution and lack of green space exacerbated the adverse effects of heatwaves on cognitive function.

Effect Modifications of Overhead-View and Eye-Level Urban Greenery on Heat-Mortality Associations: Small-Area Analyses Using Case Time Series Design and Different Greenery Measurements

BACKGROUND

The protective effect of urban greenery from adverse heat impacts remains inconclusive. Existing inconsistent findings could be attributed to the different estimation techniques used.

OBJECTIVES

We investigated how effect modifications of urban greenery on heat-mortality associations vary when using different greenery measurements reflecting overhead-view and eye-level urban greenery.

METHODS

We collected meteorological and daily mortality data for 286 territory planning units between 2005 and 2018 in Hong Kong. Three greenery measurements were extracted for each unit: a) the normalized difference vegetation index (NDVI) from Landsat remote sensing images, b) the percentage of greenspace based on land use data, and c) eye-level street greenery from street view images via a deep learning technique. Time-series analyses were performed using the case time series design with a linear interaction between the temperature term and each of the three greenery measurements. Effect modifications were also estimated for different age groups, sex categories, and cause-specific diseases.

RESULTS

Higher mortality risks were associated with both moderate and extreme heat, with relative risks (RRs) of 1.022 (95% CI: 1.000, 1.044) and 1.045 (95% CI: 1.013, 1.079) at the 90th and 99th percentiles of temperatures relative to the minimum mortality temperature (MMT). Lower RRs were observed in greener areas whichever of the three greenery measurements was used, but the disparity of RRs between areas with low and high levels of urban greenery was more apparent when using eye-level street greenery as the index at high temperatures (99th percentile relative to MMT), with RRs for low and high levels of greenery, respectively, of 1.096 (95% CI: 1.035, 1.161) and 0.985 (95% CI: 0.920, 1.055) for NDVI (p = 0.0193 ), 1.068 (95% CI: 1.021, 1.117) and 0.990 (95% CI: 0.906, 1.081) for the percentage of greenspace (p = 0.1338 ), and 1.103 (95% CI: 1.034, 1.177) and 0.943 (95% CI: 0.841, 1.057) for eye-level street greenery (p = 0.0186 ). Health discrepancies remained for nonaccidental mortality and cardiorespiratory diseases and were more apparent for older adults (≥ 65 years of age) and females.

DISCUSSION

This study provides new evidence that eye-level street greenery shows stronger associations with reduced heat-mortality risks compared with overhead-view greenery based on NDVI and percentage of greenspace. The effect modification of urban greenery tends to be amplified as temperatures rise and are more apparent in older adults and females. Heat mitigation strategies and health interventions, in particular with regard to accessible and visible greenery, are needed for helping heat-sensitive subpopulation groups in coping with extreme heat. https://doi.org/10.1289/EHP12589.

Combined effects of heatwaves and air pollution, green space and blue space on the incidence of hypertension: A national cohort study

Extreme heat exposure has been associated with hypertension. However, its interactive influences with air pollution, green and blue spaces are unclear. This study aimed to explore the interaction between heatwaves, air pollution, green and blue spaces on hypertension. Cohort data enrolled 6448 Chinese older adults aged 65 years and over were derived from the Chinese Longitudinal Healthy Longevity Survey (CLHLS) between 2008 and 2018. Nine heatwave definitions, combining three heat thresholds (92.5th, 95th, and 97.5th percentiles of daily maximum temperature) and three durations (≥2, 3 and 4 days) were used as time-varying variables in the analysis and were the one-year exposure before survival events. Fine particulate matter (PM ≤2.5 μm in aerodynamic diameter (PM_2.5)), the Normalized Difference Vegetation Index (NDVI) and the average proportion of open water bodies were used to reflect the air pollution, green and blue space exposures, respectively. PM_2.5, green and blue space exposures were time-varying indicators and contemporaneous with heatwaves. Mixed Cox models with time-varying variables were fitted to assess the multiplicative and additive interaction of heatwaves, PM_2.5, and green and blue spaces on hypertension, measured by a traditional product term with the ratio of hazard ratio (HR) and relative risk due to interaction (RERI), respectively. A positive multiplicative (HRs >1) and additive interaction (RERIs >0) between heatwaves and higher PM_2.5 levels was observed. There was a synergistic effect between heatwaves and decreasing greenness levels on hypertension incidence on additive and multiplicative scales. No significant interaction between heatwaves and blue space was observed in the analysis. The combined effects of heatwaves, air pollution, green and blue space exposures on the risk of hypertension varied with age, gender, and educational attainment. This study's findings complemented the existing evidence and revealed synergistic harmful impacts for heatwaves with air pollution and lack of green space on hypertension incidence.

Exploring Health Effects under Specific Causes of Mortality Based on 90 Definitions of PM2.5 and Cold Spell Combined Exposure in Shanghai, China

In this study, a total of 90 definitions were set up based on six air pollution definitions, five cold spell definitions, and three combined exposure scenarios. The relative risks (RRs) on all-cause, circulatory, and respiratory mortality were explored by a model combining a distributed linear lag model with quasi-Poisson regression. The definition in which daily PM_2.5 increases more than 75 μg/m³ for at least 2 days and the average temperature falls below the 10th percentile for at least 2 days produced the best model fit performance in all-cause mortality. The high peaks of the health effect were generally observed around the lag days 6-9. The cumulative relative risks (CRRs) were more significant in the simultaneous-exposure scenario and higher in respiratory mortality, where the highest CRR (12.15, 3.69-40.03) was observed in definition P1T5, in which daily PM_2.5 increases more than 75 μg/m³, and the average temperature falls below the 2.5th percentile for at least two days. For relative risk due to interaction (RERI), we found positive additive interactions (RERI > 0) between PM_2.5 pollution and cold spell, especially in respiratory mortality. Clarifying the definition of combined events can help policymakers to capture health risks and construct more effective risk warning systems.

The role of residential greenness levels, green land cover types and diversity in overweight/obesity among older adults: A cohort study

BACKGROUND

Few studies have investigated the effects of greenness exposure, green land cover types and diversity and their interaction with particulate matter (PM) to adiposity.

METHOD

Cohort data were collected from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). Baseline data on greenness levels, green land cover types and diversity were assessed by the Normalized Difference Vegetation Index (NDVI), three greenery types (trees, shrublands and grassland) and Shannon's diversity index, respectively. Body mass index (BMI) and waist circumference (WC) were separately used as dependent variables and represented for peripheral overweight/obesity and central obesity, respectively. The mixed Cox model with random intercept was used to estimate the effects of greenness levels, types and diversity on overweight/obesity using single and multiple exposure models. We also examined the interaction of PM and the aforementioned indicators on overweight/obesity on both additive and multiplicative scales.

RESULTS

Single exposure models showed that higher levels of residential greenness, tree coverage and ratio of trees to shrublands/grassland were inversely associated with peripheral overweight/obesity and central obesity. An increase in shrublands, grassland and diversity of green was related to lower odds of peripheral overweight/obesity. Multiple exposure models confirmed the association between greenness levels and peripheral overweight/obesity. Males, educated participants and elderly who lived in southern regions and areas with cleaner air environments acquired more benefits from greenspace exposure. Single and multiple exposure models indicated that an antagonistic effect of increasing PM and decreasing greenness levels on peripheral overweight/obesity and central obesity. Single exposure models showed the potential interaction of tree coverage, ratio of trees to grassland and PM_2.5 exposures on the risk of peripheral overweight/obesity.

CONCLUSION

Increasing residential greenness and diversity of green were associated with healthy weight status. The relationship between greenery and overweight/obesity varied, and the effects of greenspace exposure on overweight/obesity were associated with air pollution.

Spatiotemporal mechanism of urban heat island effects on human health—Evidence from Tianjin city of China

The increasingly intensifying global warming and urban heat island (UHIs) are seriously damaging the physical and mental health of urban residents. However, the spatiotemporal evolution of how high temperatures affect human health in megacities remains unclear. Therefore, in this study, with Tianjin during 2006–2020 as an example, and based on data from meteorological stations, Landsat remote sensing images, and point of interest big data, this study applied hot- and cold-spot statistics and remote sensing retrieval in numerical modeling and established an appraisal system to assess how and to what extent UHIs affect resident health. The results showed that the overall influence of UHIs on respiratory and cardiovascular diseases and mental health increased to 373 km2 in area and two levels in intensity; the influence was mainly concentrated in the downtown area, with a rising influence level. Owing to the dual-core structure of the city, the influence was distributed along the main traffic lines in Binhai New District, having a strong influence in the area mainly concentrated in the southeastern part. Many cold spots clustered in the central urban area to cool the thermal environment: the cooled area was 6.5 times larger than the area of intense cooling influence. Our study provides a method for identifying health risks in urban spaces, lays a theoretical foundation to improve the planning of urban green space systems, and offers some decision-making guidance for the planning of healthy cities.