Estimating the heat-related mortality and morbidity burden in the province of Quebec, Canada.

BACKGROUND: As climate change increases the frequency and intensity of extreme heat events, there is an urgent need to quantify the heat-related health burden. However, most past studies have focussed on a single health outcome (mainly mortality) or on specific heatwaves, thus providing limited knowledge of the total pressure heat exerts on health services. OBJECTIVES: This study aims to quantify the heat-related mortality and morbidity burden for five different health outcomes including all-cause mortality, hospitalizations, emergency department (ED) visits, ambulance transports and calls to a health hotline, using the province of Quebec (Canada) as a case study. METHODS: A two-step statistical analysis was employed to estimate regional heat-health relationships using Distributed Lag Non-Linear Models (DLNM) and pooled estimates using a multivariate meta-regression. Heat burden was quantified by attributable fraction (AF) and attributable number (AN) for two temperature ranges: all heat (above the minimum mortality/morbidity temperature) and extreme heat (above the 95th percentile of temperature). RESULTS: Higher temperatures were associated with greater risk ratios for all health outcomes studied, but at different levels. Significant AF ranging from 2 to 3% for the all heat effect and 0.4-1.0% for extreme heat were found for all health outcomes, except for hospitalizations that had an AF of 0.1% for both heat exposures. The estimated burden of all heat (and extreme heat) every summer across the province was 470 (200) deaths, 225 (170) hospitalizations, 36 000 (6 200) ED visits, 7 200 (1 500) ambulance transports and 15 000 (3 300) calls to a health hotline, all figures significant. DISCUSSION: This new knowledge on the total heat load will help public health authorities to target appropriate actions to reduce its burden now and in the future. The proposed state-of-the-art framework can easily be applied to other regions also experiencing the adverse effects of extreme heat.

Temporal changes in temperature-related mortality in relation to the establishment of the heat-health alert system in Victoria, Australia.

Extreme heat alerts are the most common form of weather forecasting services used in Australia, yet very limited studies have documented their effectiveness in improving health outcomes. This study aimed to examine the temporal changes in temperature-related mortality in relation to the activation of the heat-health alert and response system (HARS) in the State of Victoria, Australia. We examined the relationship between temperatures and mortality using quasi-Poisson regression and the distributed lag non-linear model (dlnm) and compared the temperature-mortality association between the two periods: period 1- prior-HARS (1992-2009) and period 2- post-HARS (2010-2019). Since the HARS heavily weights heatwave effects, we also compared the main effects of heatwave events between the two periods. The heatwaves were defined for three levels, including 3 consecutive days at 97th, 98th, and 99th percentiles. We also controlled the potential confounding effect of seasonality by including a natural cubic B-spline of the day of the year with equally spaced knots and 8 degrees of freedom per year. The exposure-response curve reveals the temperature mortality was reduced in period 2 in comparison with period 1. The relative risk ratios (RRR) of Period 2 over Period 1 were all less than one and gradually decreased from 0.86 (95% CI, 0.72-1.03) to 0.64 (95% CI, 0.33-1.22), and the differences in attributable risk percent increased from 13.2 to 25.3%. The reduction in the risk of heatwave-related deaths decreased by 3.4% (RRp1 1.068, 95% CI, 1.024-1.112 versus RRp2 1.034, 95% CI, 0.986-1.082) and 10% (RRp1 1.16, 95% CI, 1.10-1.22 versus RRp2 1.06, 95% CI, 1.002-1.119) for all groups of people. The study indicated a decrease in heat-related mortality following the operation of HARS in Victoria under extreme heat and high-intensity heatwaves conditions. Further studies could investigate the extent of changes in mortality among populations of differing socio-economic groups during the operation of the heat-health alert system.

Research Note: Water applied direct-fed microbial reduced mortality in heat stressed broilers.

Pressure to reduce the use of antibiotics in the poultry industry has intensified research on alternative solutions to support intestinal health, including but not limited to direct fed microbials (DFM). Heat stress is known to impact intestinal health and function. The aim of this study was to determine efficacy of a water applied DFM product on broiler performance during the summer period. One of two treatments were randomly allocated to 12 replicate floor pens each: a control treatment and a treatment provided daily with a dual strain DFM comprised of Lactobacillus acidophilus AG01 and Bifidobacterium animalis AG02 at 1 × 108 CFU/bird/d. Each pen contained 20 Ross 308 broilers. All birds were fed the same three-phased wheat- and soybean meal-based diets. Body weight, feed intake, feed conversion ratio, and mortality were measured at d 0, 10, 24, 35, and 42. Due to natural extreme external temperature conditions, all birds were subject to heat stress during the end of the grower phase up to and including the finisher phase. Temperature was on average 5°C higher compared to industry recommendation. No significant differences were found in growth performance between the control and DFM treatment, yet BW at d 42 in both treatments was reduced by 19% compared to the breed standard. The DFM treatment significantly reduced mortality among the birds. Overall mortality from d 1 to d 35 was reduced from 4.58% to 0.42% (P = 0.023) and overall mortality from d 1 to d 42 was reduced from 5.83 to 0.83% (P = 0.027). This was driven by the difference in heat-stress related mortality in the finisher phase from d 25 to d 42, where mortality reached only 0.44% in the DFM treatment versus 2.88% in the unsupplemented control treatment. Post-mortem analysis confirmed heat-stress related hypoxia. In conclusion, the dual strain DFM may have provided improved (intestinal) homeostasis and barrier function allowing increased resilience to heat stress in broilers.

Heat-related fatalities in North Carolina 1999-2017.

OBJECTIVES: Research shows the highest rates of occupational heat-related fatalities among farm laborers and among Black and Hispanic workers in North Carolina (NC). The Hispanic population and workforce in NC have grown substantially in the past 20 years. We describe the epidemiology of heat-related fatal injuries in the general population and among workers in NC. METHODS: We reviewed North Carolina death records and records of the North Carolina Office of the Chief Medical Examiner to identify heat-related deaths (primary International Classification of Diseases, Tenth Revision diagnosis code: X30 or T67.0-T67.9) that occurred between January 1, 1999, and December 31, 2017. Decedent age, sex, race, and ethnicity were extracted from both the death certificate and the medical examiner's report as well as determinations of whether the death occurred at work. RESULTS: In NC between 1999 and 2017, there were 225 deaths from heat-related injuries, and 25 occurred at work. The rates of occupational heat-related deaths were highest among males, workers of Hispanic ethnicity, workers of Black, multiple, or unknown race, and in workers aged 55-64. The highest rate of occupational heat-related deaths occurred in the agricultural industry. CONCLUSIONS: Since the last report (2001), the number of heat-related fatalities has increased, but fewer were identified as workplace fatalities. Rates of occupational heat-related deaths are highest among Hispanic workers. NC residents identifying as Black are disproportionately burdened by heat-related fatalities in general, with a wider apparent disparity in occupational deaths.

The effects of extreme heat on human health in tropical Africa.

This review examines high-quality research evidence that synthesises the effects of extreme heat on human health in tropical Africa. Web of Science (WoS) was used to identify research articles on the effects extreme heat, humidity, Wet-bulb Globe Temperature (WBGT), apparent temperature, wind, Heat Index, Humidex, Universal Thermal Climate Index (UTCI), heatwave, high temperature and hot climate on human health, human comfort, heat stress, heat rashes, and heat-related morbidity and mortality. A total of 5, 735 articles were initially identified, which were reduced to 100 based on a set of inclusion and exclusion criteria. The review discovered that temperatures up to 60°C have been recorded in the region and that extreme heat has many adverse effects on human health, such as worsening mental health in low-income adults, increasing the likelihood of miscarriage, and adverse effects on well-being and safety, psychological behaviour, efficiency, and social comfort of outdoor workers who spend long hours performing manual labour. Extreme heat raises the risk of death from heat-related disease, necessitating preventative measures such as adaptation methods to mitigate the adverse effects on vulnerable populations during hot weather. This study highlights the social inequalities in heat exposure and adverse health outcomes.

Hot weather and heat extremes: health risks.

Hot ambient conditions and associated heat stress can increase mortality and morbidity, as well as increase adverse pregnancy outcomes and negatively affect mental health. High heat stress can also reduce physical work capacity and motor-cognitive performances, with consequences for productivity, and increase the risk of occupational health problems. Almost half of the global population and more than 1 billion workers are exposed to high heat episodes and about a third of all exposed workers have negative health effects. However, excess deaths and many heat-related health risks are preventable, with appropriate heat action plans involving behavioural strategies and biophysical solutions. Extreme heat events are becoming permanent features of summer seasons worldwide, causing many excess deaths. Heat-related morbidity and mortality are projected to increase further as climate change progresses, with greater risk associated with higher degrees of global warming. Particularly in tropical regions, increased warming might mean that physiological limits related to heat tolerance (survival) will be reached regularly and more often in coming decades. Climate change is interacting with other trends, such as population growth and ageing, urbanisation, and socioeconomic development, that can either exacerbate or ameliorate heat-related hazards. Urban temperatures are further enhanced by anthropogenic heat from vehicular transport and heat waste from buildings. Although there is some evidence of adaptation to increasing temperatures in high-income countries, projections of a hotter future suggest that without investment in research and risk management actions, heat-related morbidity and mortality are likely to increase.

Exertional heat fatalities in Australian sport and recreation.

OBJECTIVES: To describe the number and case characteristics of sport and recreation-related exertional heat deaths in Australia and summarise recommendations derived from case narratives. DESIGN: Descriptive, population-based, retrospective cohort study. METHODS: Cases were identified using the National Coronial Information System (NCIS) through multiple search strategies comprising queries, keywords and cause of death codes. Cases were included where there was evidence that the deceased was actively engaged in sport or recreation and exertional heat illness was causal or contributory to the death. Data extraction were performed independently, in duplicate, to ensure accuracy. Descriptive statistics are used to report deceased's socio-demographic characteristics, incident characteristics, type of sport/recreational activity and time sequence of events. Content analysis is used to summarise recommendations. RESULTS: Thirty-eight deaths (males n = 29, 74%; median age = 40 years, range 8-77) were identified during the study period (2001 to 2018), with 22 recommendations for five cases. Two cases occurred during organised sport and 36 during active recreation, of which 27 were in hiking. Eleven (29%) individuals were international visitors. There were 22 recommendations across 5 cases presented, with a focus on education and training. CONCLUSIONS: Exertional heat deaths in outdoor recreation in Australia were far more prevalent than cases in organised sport. The largest proportion of deaths occurred in hiking with two populations featuring: males aged 15-45 years and international visitors. Considering the incident characteristics and time sequence of events, measures such as early recognition of symptoms, provision of first aid and timely access to emergency medical care are important to prevent fatalities.

Cardiovascular control during heat stress in older adults: time for an update.

It is generally accepted that older adults display an impaired cardiovascular response to heat stress, and it has been suggested that this impaired response contributes to their increased risk of mortality during extreme heat events. Seminal studies have shown that cutaneous vasodilation, the redistribution of blood flow from visceral organs, and the increase in cardiac output are blunted in older adults during passive heating. The blunted rise of cardiac output was initially attributed to an inability to maintain stroke volume, suggesting that cardiac systolic and/or diastolic function does not adequately respond to the constraints of heat stress in older adults. Recent studies evaluated potential mechanisms underlying these seminal findings and their results challenge some of these initial observations. Notably, stroke volume is maintained during heat exposure in older adults and studies have provided evidence for preserved cardiac systolic and diastolic functions in this population. Nonetheless, a blunted increase in cardiac output during heat exposure remains a consistent observation in older adults, although it is now attributed to a blunted increase in heart rate. Recent studies have also evaluated the possibility that the attenuated capacity of aged skin to vasodilate contributes to a blunted increase in cardiac output during heat stress. The objective of this Mini-Review is to highlight these recent advances and challenge the long-standing view that the control of stroke volume during heat exposure is compromised in older adults. By doing so, our intent is to stimulate future studies to evaluate several unanswered questions in this area of research.

Thermal stress-induced oxidative damages in the liver and associated death in fish, Labeo rohita.

Fish mortality generally occurs during extreme summer temperatures in India which are apprehended to be more frequent in near future and may reduce the fish population, particularly in closed aquatic systems. This present study is conducted with the objectives to find out heat shock and associated oxidative stress responses that occurred in selected fish Labeo rohita due to extremely high water temperature (treated, 37-38 °C against control, 28-30 °C) exposure for 2 weeks. Calculated mortality was 30% during the experimental period. The results revealed the biomolecules associated with both the anti-oxidative response (reduced glutathione in serum, liver, muscle; catalase activity in liver, muscle; superoxide dismutase gene expression in the liver) and the heat shock response (hsp70 gene expression in the liver) were elevated under thermal stress. Pro-inflammatory responses (expression of complement protein 3, glyceraldehyde 3-phosphate dehydrogenase in the liver) and oxidative damages (lipid peroxidation in all studied tissue and DNA fragmentation in the liver) were more under thermal stress. Extreme thermal stress induced by partial lethal temperature exposure in this study led to the activation of both the heat shock response and the anti-oxidative response. However, these responses were not elicited to the level so that they can protect from oxidative damages and inflammation in the liver of all the studied fish that caused partial mortality in fish. Thermal stress-induced hepatotoxicity caused fish death which was documented for the first time in freshwater fish.

Analysis of D-dimer cut-off values for overt DIC diagnosis in exertional heat illness.

ABSTRACT: The International Society on Thrombosis and Haemostasis (ISTH) scoring system has been used for diagnosing overt disseminated intravascular coagulation (DIC). However, the cut-off points of fibrin-related markers remain unclear. The ability of the ISTH DIC score and Multiple Organ Dysfunction (MODS) score to predict mortality in cases of exertional heat illness (EHI) was tested. In the process, 3 different D-dimer cut-off values for diagnosing overt DIC were evaluated.Data were obtained on the first day of hospitalization for 76 patients with EHI. The DIC score was calculated according to the ISTH scoring system using 3 D-dimer cut-off values.In predicting mortality, methods 1 and 2 had the same sensitivity and specificity, which were 85% and 73.2%, respectively. The sensitivity for method 3 was 70%. Furthermore, the specificity of the DIC score for method 3 was 89%, which was higher than that of the other 2 methods. The correlation coefficients of the DIC and MODS scores of these 3 methods were 0.757, 0.748, and 0.756, respectively. For the prediction of mortality, the area under the receiver operating characteristic (ROC) curve for the DIC scores of these 3 methods was 0.838, 0.842, and 0.85, respectively. Furthermore, the area under the ROC curve of the MODS score was 0.927.The DIC score had a certain predictive power of a poor outcome of EHI patients, but this was not better than the MODS score. The present data may serve as a reference in selecting the appropriate D-dimer cut-off point for the ISTH DIC score.

Social inequalities in heat-attributable mortality in the city of Turin, northwest of Italy: a time series analysis from 1982 to 2018.

BACKGROUND: Understanding context specific heat-health risks in urban areas is important, especially given anticipated severe increases in summer temperatures due to climate change effects. We investigate social inequalities in the association between daily temperatures and mortality in summer in the city of Turin for the period 1982-2018 among different social and demographic groups such as sex, age, educational level, marital status and household occupants. METHODS: Mortality data are represented by individual all-cause mortality counts for the summer months between 1982 and 2018. Socioeconomic level and daily mean temperature were assigned to each deceased. A time series Poisson regression with distributed lag non-linear models was fitted to capture the complex nonlinear dependency between daily mortality and temperature in summer. The mortality risk due to heat is represented by the Relative Risk (RR) at the 99th percentile of daily summer temperatures for each population subgroup. RESULTS: All-cause mortality risk is higher among women (1.88; 95% CI = 1.77, 2.00) and the elderly (2.13; 95% CI = 1.94, 2.33). With regard to education, the highest significant effects for men is observed among higher education levels (1.66; 95% CI = 1.38, 1.99), while risks for women is higher for the lower educational level (1.93; 95% CI = 1.79, 2.08). Results on marital status highlighted a stronger association for widower in men (1.66; 95% CI = 1.38, 2.00) and for separated and divorced in women (2.11; 95% CI = 1.51, 2.94). The risk ratio of household occupants reveals a stronger association for men who lived alone (1.61; 95% CI = 1.39, 1.86), while for women results are almost equivalent between alone and not alone groups. CONCLUSIONS: The associations between heat and mortality is unequal across different aspects of social vulnerability, and, inter alia, factors influencing the population vulnerability to temperatures can be related to demographic, social, and economic aspects. A number of issues are identified and recommendations for the prioritisation of further research are provided. A better knowledge of these effect modifiers is needed to identify the axes of social inequality across the most vulnerable population sub-groups.

Heat-Associated Mortality in a Hot Climate : Maricopa County, Arizona, 2006-2016.

OBJECTIVES: Maricopa County, Arizona (2017 population about 4.3 million), is located in the Sonoran Desert. In 2005, the Maricopa County Department of Public Health (MCDPH) established a heat-associated mortality surveillance system that captures data on circumstances of death for Maricopa County residents and visitors. We analyzed 2006-2016 surveillance system data to understand the characteristics and circumstances of heat-associated deaths. METHODS: We classified heat-associated deaths based on International Classification of Diseases, Tenth Revision codes (X30, T67.X, and P81.0) and phrases (heat exposure, environ, exhaustion, sun, heat stress, heat stroke, or hyperthermia) in part I or part II of the death certificate. We summarized data on decedents' demographic characteristics, years lived in Arizona, location of death (indoors vs outdoors), presence and functionality of air conditioning, and whether the decedent had been homeless. We examined significant associations between variables by using the Pearson χ2 tests and logistic regression. RESULTS: During 2006-2016, MCDPH recorded data on 920 heat-associated deaths, 912 of which included location of injury. Of 565 (62%) heat-associated deaths that occurred outdoors, 458 (81%) were among male decedents and 243 (43%) were among decedents aged 20-49. Of 347 (38%) heat-associated deaths that occurred indoors, 201 (58%) were among decedents aged ≥65. Non-Arizona residents were 5 times as likely as Arizona residents to have a heat-associated death outdoors (P < .001). Of 727 decedents with data on duration of Arizona residency, 438 (60%) had resided in Arizona ≥20 years. CONCLUSIONS: Ongoing evaluation of interventions that target populations at risk for both outdoor and indoor heat-associated deaths can further inform refinement of the surveillance system and identify best practices to prevent heat-associated deaths.

Future increase in elderly heat-related mortality of a rapidly growing Asian megacity.

Urban dwellers are at risk of heat-related mortality in the onset of climate change. In this study, future changes in heat-related mortality of elderly citizens were estimated while considering the combined effects of spatially-varying megacity's population growth, urbanization, and climate change. The target area is the Jakarta metropolitan area of Indonesia, a rapidly developing tropical country. 1.2 × 1.2 km2 daily maximum temperatures were acquired from weather model outputs for the August months from 2006 to 2015 (present 2010s) and 2046 to 2055 (future 2050s considering pseudo-global warming of RCP2.6 and RCP8.5). The weather model considers population-induced spatial changes in urban morphology and anthropogenic heating distribution. Present and future heat-related mortality was mapped out based on the simulated daily maximum temperatures. The August total number of heat-related elderly deaths in Jakarta will drastically increase by 12~15 times in the 2050s compared to 2010s because of population aging and rising daytime temperatures under "compact city" and "business-as-usual" scenarios. Meanwhile, mitigating climate change (RCP 2.6) could reduce the August elderly mortality count by up to 17.34%. The downwind areas of the densest city core and the coastal areas of Jakarta should be avoided by elderly citizens during the daytime.

Deaths in Australia from Work-Related Heat Stress, 2000-2015.

The infrequency of deaths from work-related heat stress may be due to self-pacing, whereby workers adjust their work rate in response to thermal discomfort. Thirteen cases attributed after coronial investigation to work-related heat stress were studied to evaluate the causal contribution of environmental and personal risk factors. Meteorological records and coronial records were examined to estimate environmental and metabolic heat loads and to identify any personal risk factors likely to have contributed to death. Seven deaths occurred in workers within one week of hiring, demonstrating not only the importance of acclimatisation but also the likelihood of compromised self-pacing in recently-hired workers. Personal risk factors identified included intercurrent illness, cardiovascular disease and obesity. Four deaths occurred following indoor work, where the probable critical risk parameter was low air velocity. Cerebral and pulmonary oedema were reported in some autopsy reports, and uncal herniation was found in one case. Modified work rates and close supervision are essential in recently-hired workers. The risk of death from raised intracranial pressure suggests the need for specific remediation of cerebral oedema in hyperthermic individuals.

Heat-related deaths among construction workers in the United States.

BACKGROUND: Heat is a severe hazard for construction workers and may be worsening with global warming. This study sought to explore heat-related deaths among U.S. construction workers and a possible association with climate change. METHODS: Heat-related deaths in the Census of Fatal Occupational Injuries from 1992 to 2016 were analyzed. Denominators estimated from the Current Population Survey were matched with demographic and occupational categories in rate calculations. Statistical tests were used to examine heat-related deaths in relation to time, geographic region, and temperature. RESULTS: Construction workers, comprising 6% of the total workforce, accounted for 36% (n = 285) of all occupational heat-related deaths from 1992 to 2016 in the U.S. Mean temperatures from June to August increased gradually over the study period. Increasing summer temperatures from 1997 to 2016 were associated with higher heat-related death rates (r = 0.649; 95% confidence interval: 0.290, 0.848). Compared to all construction workers (risk index = 1), statistically significant elevated risk of heat-related death was found among Hispanics (1.21), in particular workers born in Mexico (1.91). Occupations with a high risk index included cement masons (10.80), roofers (6.93), helpers (6.87), brick masons (3.33), construction laborers (1.93) and heating, air conditioning, and refrigeration mechanics (1.60). CONCLUSIONS: U.S. construction workers are at a high risk of heat-related death, and this risk has increased with climate change over time. Effective workplace interventions, enhanced surveillance, and improved regulations and enforcement should accompany broader efforts to combat global warming. The construction industry can help reduce global warming through increased implementation of green building principles.

Heat Stress Impacts on Cardiac Mortality in Nepali Migrant Workers in Qatar.

BACKGROUND: Qatar is a major destination country for Nepali migrant workers (NMWs; main age range 25-35 years) in the construction trade. These 120,000+ NMWs are exposed to various occupational hazards, including excessive heat, and 3-4 workers die each week. Our study aimed to show whether heat exposure caused deaths. METHODS: The worker population and mortality data of NMWs were retrieved from government institutions in Nepal. Heat exposure was assessed by monthly estimates of daily wet bulb globe temperature (WBGT), for in-shade conditions, from data collected at the Doha weather station from 2009 to 2017. Working in the sun during the middle of the day would add 2-3°C to the in-shade WBGT values. Daily deaths and their causes were obtained from the records of the Foreign Employment Promotion Board (FEPB) in Nepal, 2009-2017. Interviews with returning NMWs about their working conditions and the impacts of these conditions added information. The association between the heat variable and mortality was tested with standard statistical methods. RESULTS: The average annual death rate for NMWs in Qatar was 150 deaths/100,000. According to interviews, the majority of NMWs were found working in high WBGT (>31°C) each working day during hot months. The major cause of these deaths was recorded as cardiovascular problems (cardiovascular disease; CVD). Unfortunately, the causes of death were poorly described, and many deaths were listed as "cardiac arrest." We included these deaths in the broader category of "cardiovascular causes." There was a strong correlation between average monthly afternoon heat levels (WBGT) and CVD mortality. It is likely that a large proportion of these CVD deaths during hot months were due to serious heat stroke. Global studies show that approximately 15% of deaths in the age group 25-35 years are due to CVD causes. However, in this NMW population, the figures were 22% during the cool season and 58% during the hot season. CONCLUSIONS: The increased CVD mortality during hot periods is most likely due to severe heat stress. As many as 200 of the 571 CVD deaths during 2009-2017 could have been prevented if effective heat protection had been implemented as a part of local occupational health and safety programs. There is an urgent need for protection against such heat effects among NMWs, and rising temperatures from ongoing climate change are further increasing the health risks. Cause of death records for workers dying in hot conditions should be more precise than "cardiac arrest."

Increasing mitigation ambition to meet the Paris Agreement's temperature goal avoids substantial heat-related mortality in U.S. cities.

Current greenhouse gas mitigation ambition is consistent with ~3°C global mean warming above preindustrial levels. There is a clear need to strengthen mitigation ambition to stabilize the climate at the Paris Agreement goal of warming of less than 2°C. We specify the differences in city-level heat-related mortality between the 3°C trajectory and warming of 2° and 1.5°C. Focusing on 15 U.S. cities where reliable climate and health data are available, we show that ratcheting up mitigation ambition to achieve the 2°C threshold could avoid between 70 and 1980 annual heat-related deaths per city during extreme events (30-year return period). Achieving the 1.5°C threshold could avoid between 110 and 2720 annual heat-related deaths. Population changes and adaptation investments would alter these numbers. Our results provide compelling evidence for the heat-related health benefits of limiting global warming to 1.5°C in the United States.

The Use of a Quasi-Experimental Study on the Mortality Effect of a Heat Wave Warning System in Korea.

Many cities and countries have implemented heat wave warning systems to combat the health effects of extreme heat. Little is known about whether these systems actually reduce heat-related morbidity and mortality. We examined the effectiveness of heat wave alerts and health plans in reducing the mortality risk of heat waves in Korea by utilizing the discrepancy between the alerts and the monitored temperature. A difference-in-differences analysis combined with propensity score weighting was used. Mortality, weather monitoring, and heat wave alert announcement data were collected for 7 major cities during 2009-2014. Results showed evidence of risk reduction among people aged 19-64 without education (-0.144 deaths/1,000,000 people, 95% CI: -0.227, -0.061) and children aged 0-19 (-0.555 deaths/1,000,000 people, 95% CI: -0.993, -0.117). Decreased cardiovascular and respiratory mortality was found in several subgroups including single persons, widowed people, blue-collar workers, people with no education or the highest level of education (university or higher). No evidence was found for decreased all-cause mortality in the population (1.687 deaths/1,000,000 people per day; 95% CI: 1.118, 2.255). In conclusion, heat wave alerts may reduce mortality for several causes and subpopulations of age and socio-economic status. Further work needs to examine the pathways through which the alerts impact subpopulations differently.