Using the Excess Heat Factor (EHF) to predict the risk of heat related deaths

Increasing tree cover and high-albedo surfaces reduces heat-related ER visits in Los Angeles, CA

There is an urgent need for strategies to reduce the negative impacts of a warming climate on human health. Cooling urban neighborhoods by planting trees and vegetation and increasing albedo of roofs, pavements, and walls can mitigate urban heat. We used synoptic climatology to examine how different tree cover and albedo scenarios would affect heat-related morbidity in Los Angeles, CA, USA, as measured by emergency room (ER) visits. We classified daily meteorological data for historical summer heat events into discrete air mass types. We analyzed those classifications against historical ER visit data to determine both heat-related and excess morbidity. We used the Weather Research and Forecasting model to examine the impacts of varied tree cover and albedo scenarios on meteorological outcomes and used these results with standardized morbidity data algorithms to estimate potential reductions in ER visits. We tested three urban modification scenarios of low, medium, and high increases of tree cover and albedo and compared these against baseline conditions. We found that avoiding 25% to 50% of ER visits during heat events would be a common outcome if the urban environment had more tree cover and higher albedo, with the greatest benefits occurring under heat events that are moderate and those that are particularly hot and dry. We conducted these analyses at the county level and compared results to a heat-vulnerable, working-class Los Angeles community with a high concentration of people of color, and found that reductions in the rate of ER visits would be even greater at the community level compared to the county.

Spatiotemporal variation in heatwaves and elderly population exposure across China

Heatwaves have been intensified worldwide due to climate change, posing great health risks, especially to elderly populations. However, in China, limited studies have employed the heat index to decipher the spatiotemporal trends of heatwaves and their impacts on the elderly population. By comparing the three heatwave definitions, this study aimed to evaluate the long-term spatiotemporal variations in heatwaves from 1964 to 2022 across China using the Excess Heat Factor (EHF). We took advantage of high-resolution reanalysis temperature data on the Google Earth Engine (GEE) platform to efficiently calculate the heatwaves. Our results revealed that the frequency and duration of heatwaves increased significantly in approximately 77 % of China's total area, with South China experiencing the most frequent and prolonged heatwaves. Conversely, in most areas, no significant trend was discerned in the growth of the maximum and average heatwave intensities. The total number of elderly people affected by heatwaves surged from approximately 11.96 million in 2001 to over 30.31 million in 2020, with an estimated additional 1.12 million older adults exposed to heatwaves annually across the nation (R2 = 0.60, p < 0.05). The population factor exhibited largest effect on the exposure of heatwaves, followed by climate effects and combined factors, with the corresponding explanatory power about 42.84 %, 34.85 % and 22.31 %, respectively. These individuals predominantly resided in the Northeast China, Southwest China, and South China. We also found geographical variations in heatwave exposure along elevations and land use types. These insights underscore the pressing necessity for formulating strategic interventions to mitigate the health threats presented by mounting heatwave exposure, especially for susceptible groups like the elderly in China.

A 43-year of human thermal comfort in Central Africa

In this study, the human thermal stress was quantified across Central Africa (C.A.) using the Universal Thermal Climate Index (UTCI). Although many of the documented studies on the use of UTCI in relation to human health are currently restricted to countries in the northern hemisphere, this contribution constitutes a prerequisite of information for future research in the region. To mitigate the problem of lack of field data in the Central African sub-region, we downloaded UTCI data via the ERA5 reanalysis portal. Based on this data source, we have explored the spatiotemporal characteristics and the resulting behaviour at annual, seasonal and monthly scales in Central Africa over the period 1982 to 2022. On these different scales, 4 of the 10 UTCI thermal stress categories were experienced, ranging from mild cold stress to strong heat stress. Spatially, cases of moderate heat stress were the most widespread, with cases of strong intensity occurring in a few isolated areas in the centre, east and west. Slight cold stress is confined to the south-east domain, particularly in autumn and winter. From 1982 to 2022, heat stress has increased significantly in the region, with peaks observed in January and October; very few areas have been spared the phenomenon of thermal stress. However, a slight decreasing trend was noticed along coastal regions and the south of C.A. Thereafter, the trend values showed the degree of C.A. vulnerability to global warming, and thus appropriate measures should be taken in relation to outdoor occupations and its impacts on the population of this region.

Estimating the Burden of Heat-Related Illness Morbidity Attributable to Anthropogenic Climate Change in North Carolina

Climate change is known to increase the frequency and intensity of hot days (daily maximum temperature ≥30°C), both globally and locally. Exposure to extreme heat is associated with numerous adverse human health outcomes. This study estimated the burden of heat-related illness (HRI) attributable to anthropogenic climate change in North Carolina physiographic divisions (Coastal and Piedmont) during the summer months from 2011 to 2016. Additionally, assuming intermediate and high greenhouse gas emission scenarios, future HRI morbidity burden attributable to climate change was estimated. The association between daily maximum temperature and the rate of HRI was evaluated using the Generalized Additive Model. The rate of HRI assuming natural simulations (i.e., absence of greenhouse gas emissions) and future greenhouse gas emission scenarios were predicted to estimate the HRI attributable to climate change. Over 4 years (2011, 2012, 2014, and 2015), we observed a significant decrease in the rate of HRI assuming natural simulations compared to the observed. About 3 out of 20 HRI visits are attributable to anthropogenic climate change in Coastal (13.40% [IQR: -34.90,95.52]) and Piedmont (16.39% [IQR: -35.18,148.26]) regions. During the future periods, the median rate of HRI was significantly higher (78.65%: Coastal and 65.85%: Piedmont), assuming a higher emission scenario than the intermediate emission scenario. We observed significant associations between anthropogenic climate change and adverse human health outcomes. Our findings indicate the need for evidence-based public health interventions to protect human health from climate-related exposures, like extreme heat, while minimizing greenhouse gas emissions.

The Impact of Extreme Heat Events on Emergency Departments in Canadian Hospitals

INTRODUCTION

Mean daily temperatures in Canada rose 1.7°C between 1948 and 2016, and the frequency, severity, and duration of extreme heat events has increased. These events can exacerbate underlying health conditions, bringing patients to emergency departments (EDs). This retrospective analysis assessed the impact of temperature and humidex on ED volume and length of stay (LOS).

METHODS

LOS is an indicator of ED overcrowding and system performance. Using daily maximum temperatures and humidex values, this study investigated the impact of mean 3-d temperatures and humidex preceding ED presentation on the median and maximum ED LOS and patient volume in 2 community hospitals in Montreal, Quebec, during the summer months of 2016 to 2018. Data were analyzed with 1-way analysis of variance with post hoc Fisher least significant difference tests and Spearman correlation tests.

RESULTS

The mean maximum temperature and humidex were 26.1°C and 30.4°C, respectively (n=276 d). Mean 3-d temperatures ≥30°C were associated with higher daily ED volumes in both hospitals (138 vs 121, P=0.002 and 132 vs 125, P=0.03) and with increased median LOS at 1 hospital (8.9 vs 7.6 h, P=0.03). Mean 3-d humidex ≥35 was associated with higher daily ED volumes at both hospitals as well (136 vs 123, P=0.01 and 133 vs 125, P=0.009) with an increased median LOS at 1 hospital (8.6 vs 6.9 h, P=0.0001) with humidex values of 25 to 29.9°C.

CONCLUSIONS

Heat events were associated with increased ED presentations and LOS. This study suggests that a warming climate can impede emergency service provision by increasing the demand for and delaying timely care.

Heat-related mortality at the beginning of the twenty-first century in Rio de Janeiro, Brazil

Temperature record-breaking events, such as the observed more intense, longer-lasting, and more frequent heat waves, pose a new global challenge to health sectors worldwide. These threats are of particular interest in low-income regions with limited investments in public health and a growing urban population, such as Brazil. Here, we apply a comprehensive interdisciplinary climate-health approach, including meteorological data and a daily mortality record from the Brazilian Health System from 2000 to 2015, covering 21 cities over the Metropolitan Region of Rio de Janeiro. The percentage of absolute mortality increase due to summer extreme temperatures is estimated using a negative binomial regression modeling approach and maximum/minimum temperature-derived indexes as covariates. Moreover, this study assesses the vulnerability to thermal stress for different age groups and both genders and thoroughly analyzes four extremely intense heat waves during 2010 and 2012 regarding their impacts on the population. Results showed that the highest absolute mortality values during heat-related events were linked to circulatory illnesses. However, the highest excess of mortality was related to diabetes, particularly for women within the elderly age groups. Moreover, results indicate that accumulated heat stress conditions during consecutive days preferentially preceded by persistent periods of moderate-temperature, lead to higher excess mortality rather than sporadic single hot days. This work may provide directions in human health policies related to extreme climate events in large tropical metropolitan areas from developing countries, contributing to altering the historically based purely reactive response.

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 the excess heat factor to indicate heatwave-related urinary disease: a case study in Adelaide, South Australia

The excess heat factor (EHF) is being adopted nationally for heatwave forecasting in Australia, but there is limited research utilizing it as a predictor for heat-related morbidity from diseases of the urinary system (urinary diseases). In this study, the incidence of eight temperature-prone specific urinary disease categories was analyzed in relation to the EHF. Daily data for maximum and minimum temperature and data for metropolitan hospital emergency department presentations and inpatient admissions for urinary disease were acquired in Adelaide, South Australia, from 1 July 2003 to 31 March 2014. An increased incidence for urolithiasis, acute kidney injury (AKI), chronic kidney disease, and lower urinary tract infections was associated with the EHF. Using the Australian national heatwave definition with the EHF, emergency department presentations increased on heatwave days compared to non-heatwave days for total urinary disease (IRR 1.046, 95% CI 1.016-1.076), urolithiasis (IRR 1.106, 95% 1.046-1.169), and acute kidney injury (AKI) (IRR 1.416, 95% CI 1.258-1.594). Likewise, inpatient admissions increased for total urinary disease (IRR 1.090, 95% CI 1.048-1.133) and AKI (IRR 1.335, 95% CI 1.204-1.480). The EHF is a reliable metric for predicting heat-induced morbidity from urinary disease. Climate change-related elevations in temperature can increase morbidity from urinary disease, especially AKI and urolithiasis. Diseases of the urinary system should be highlighted when providing public health guidance during heatwaves indicated by the EHF.

What do we know about the healthcare costs of extreme heat exposure? A comprehensive literature review

Exposure to extreme heat can lead to a range of heat-related illnesses, exacerbate pre-existing health conditions and cause increased demand on the healthcare system. A projected increase in temperature may lead to greater healthcare expenditure, however, at present the costs of heat-related healthcare utilization is under-researched. This study aims to review the literature on heat-related costs for the healthcare system with a focus on ED visits, hospitalization, and ambulance call-outs. PubMed, Scopus, and Embase were used to search relevant literature from database inception to December 2017 and limited to human studies and English language. After screening, a total of ten papers were identified for final inclusion. In general, the healthcare costs of heat extremes have been poorly investigated in developed countries and not reported in developing countries where the largest heat-vulnerable populations reside. Studies showed that exposure to extreme heat was causing a substantial economic burden on healthcare systems. Females, the elderly, low-income families, and ethnic minorities had the highest healthcare costs on a range of health services utilization. Although a few studies have estimated heat healthcare costs, none of them quantified the temperature-healthcare cost relationship. There is a need to systematically examine heat-attributable costs for the healthcare system in the context of climate change to better inform heat-related policy making, target interventions and resource allocation.

Mining Social Media to Identify Heat Waves

Heat waves are one of the deadliest of natural hazards and their frequency and intensity will likely increase as the climate continues to warm. A challenge in studying these phenomena is the lack of a universally accepted quantitative definition that captures both temperature anomalies and associated mortality. We test the hypothesis that social media mining can be used to identify heat wave mortality. Applying the approach to India, we find that the number of heat-related tweets correlates with heat-related mortality much better than traditional climate-based indicators, especially at larger scales, which identify many heat wave days that do not lead to excess mortality. We conclude that social media based heat wave identification can complement climatic data and can be used to: (1) study heat wave impacts at large scales or in developing countries, where mortality data are difficult to obtain and uncertain, and (2) to track dangerous heat wave events in real time.

Assessing Heat Waves over Greece Using the Excess Heat Factor (EHF)

Heat waves are considered one of the most noteworthy extreme events all over the world due to their crucial impacts on both society and the environment. For the present article, a relatively new heat wave index, which was primarily introduced for the study of extreme warming conditions over Australia (Excess Heat Factor (EHF, hereafter)), was applied over Greece (eastern Mediterranean) for a 55-year period in order to examine its applicability to a region with different climatic characteristics (compared to Australia) and its ability to define previous exceptional heat waves. The computation of the EHF index for the period 1958–2012 demonstrated that, during the warm period of the year (June, July, August, and September (JJAS)), Greece experiences approximately 20 days per year with positive anomalous conditions (EHF > 0) with positive statistically significant trends for all stations under study. Moreover, an average of 128 spells with a duration of 3 to 10 consecutive days with positive EHF values were found during the examined 55-year period. As the duration of the spell was extended, their frequency lessened. Finally, it was found that the EHF index not only detected, identified, and described efficiently the characteristics of the heat waves, but it also provided additional useful information regarding the impact of these abnormal warming conditions on the human ability to adapt to them.

Performance of Excess Heat Factor Severity as a Global Heatwave Health Impact Index

The establishment of an effective policy response to rising heatwave impacts is most effective when the history of heatwaves, their current impacts and future risks, are mapped by a common metric. In response meteorological agencies aim to develop seamless climate, forecast, and warning heat impact services, spanning all temporal and spatial scales. The ability to diagnose heatwave severity using the Excess Heat Factor (EHF) has allowed the Australian Bureau of Meteorology (the Bureau) to publicly release 7-day heatwave severity maps since 2014. National meteorological agencies in the UK and the United States are evaluating global 7-day and multi-week EHF heatwave severity probability forecasts, whilst the Bureau contributes to a Copernicus project to supply the health sector with global EHF severity heatwave projection scenarios. In an evaluation of impact skill within global forecast systems, EHF intensity and severity is reviewed as a predictor of human health impact, and extended using climate observations and human health data for sites around the globe. Heatwave intensity, determined by short and long-term temperature anomalies at each locality, is normalized to permit spatial analysis and inter-site comparison. Dimensionless heatwave event moments of peak severity and accumulated severity are shown to correlate with noteworthy events around the globe, offering new insights into current and future heatwave variability and vulnerability. The EHF severity metric permits the comparison of international heatwave events and their impacts, and is readily implemented within international heatwave early warning systems.

Regional morbidity and mortality during heatwaves in South Australia

Heatwaves can be a common occurrence in Australia, and the public health impacts can be severe. Heat warnings and interventions are being adopted widely to reduce the preventable health impacts. This study examines the effects of heatwaves on morbidity and mortality in different climatic regions in the state of South Australia, to inform the targeting of heat warnings according to regional needs. Heatwaves were defined using the excess heat factor (EHF), an index based on mean daily temperature indices that quantifies heatwave severity relative to the local climate. In all regions, there were increases in morbidity (daily rates of ambulance call-outs and heat-related emergency presentations and hospital admissions) on heatwave days compared to non-heatwave days, which increased with heatwave severity. This study demonstrates that a consistent measure for heatwave severity, based on EHF, can be used to underpin public health warnings for climatically diverse areas.

Can the Excess Heat Factor Indicate Heatwave-Related Morbidity? A Case Study in Adelaide, South Australia

Although heatwave-related excess mortality and morbidity have been widely studied, results are not comparable spatially and often longitudinally because of different heatwave definitions applied. The excess heat factor (EHF) quantifies heatwave intensity relative to the local climate, enabling cross-regional comparisons. Previous studies have shown a strong relationship between EHFs and daily mortality during severe heatwaves. An extensive study about the relationship between EHFs and daily morbidity compared to the currently applied heatwave thresholds in Adelaide has not yet been undertaken. This paper analyzes the association of EHFs with daily morbidity between 2008 and 2014 in the Adelaide metropolitan region, South Australia, and probes three different approaches to calculate the EHF. The EHF is found to differentiate days with heatwave-related excess morbidity significantly better than other widely used weather parameters, resulting in fewer days per year with heatwave alerts than using previously proposed methods. The volume of excess morbidity can be predicted by the EHF more reliably with a model proposed for the SA Ambulance Service to support their heatwave preparation plan.

Injury patterns and features of cycling fatalities in South Australia

There has been an increase in cycling in Australia. This means that more cyclists are at risk of injuries, which account for a proportion of transport-related fatalities. In this study, all cyclist fatalities from 2002 to 2013 in South Australia where post-mortem examinations were performed were investigated. There were 42 deaths representing 3% of the total road fatalities over the same time. Of this total number of cases, 13 deaths (31%) involved collapse (mostly natural causes from an underlying medical condition) and 29 (69%) resulted from trauma. There were no cases of hyperthermia. Of the decedents 95% were male, and the mean age at death was 47 years. Fatal incidents were more likely to occur during April and November, and on a Monday. However, statistical analysis was not possible due to the small number of cases. Fatalities (traumatic and collapse) predominantly occurred whilst the cyclist was riding (86%). The majority of riding fatalities were as a result of collision with vehicles (81%). Drugs (including alcohol) were detected in two (15%) of the 13 cases of the collapses, and in seven (26%) of the 27 trauma cases tested. In trauma cases, death was most often due to multiple injuries. The most frequent area for injury was the head (found in 90% of traumatic deaths). Despite the increasing numbers of cyclists on South Australian roads over the last decade, death rates have trended downwards suggesting that road safety campaigns and the provision of more dedicated bicycle lanes have had a positive outcome.

The excess heat factor: a metric for heatwave intensity and its use in classifying heatwave severity

Heatwaves represent a significant natural hazard in Australia, arguably more hazardous to human life than bushfires, tropical cyclones and floods. In the 2008/2009 summer, for example, many more lives were lost to heatwaves than to that summer’s bushfires which were among the worst in the history of the Australian nation. For many years, these other forms of natural disaster have received much greater public attention than heatwaves, although there are some signs of change. We propose a new index, called the excess heat factor (EHF) for use in Australian heatwave monitoring and forecasting. The index is based on a three-day-averaged daily mean temperature (DMT), and is intended to capture heatwave intensity as it applies to human health outcomes, although its usefulness is likely to be much broader and with potential for international applicability. The index is described and placed in a climatological context in order to derive heatwave severity. Heatwave severity, as characterised by the climatological distribution of heatwave intensity, has been used to normalise the climatological variation in heatwave intensity range across Australia. This methodology was used to introduce a pilot national heatwave forecasting service for Australia during the 2013/2014 summer. Some results on the performance of the service are presented.