Heat illnesses: a hot topic in the setting of global climate change.

BACKGROUND: Heat illnesses affect a large number of people every year and are becoming an increasing cause of pathology as climate change results in increasing global temperatures. OBJECTIVE: This article will review the physiological responses to heat, as well as the pathophysiological processes that result in heat illnesses. The emphasis will be on providing general practitioners (GPs) with an understanding of how to prevent heat illness in their patients and how to predict who is most at risk. DISCUSSION: Heat illnesses may be thought of as minor or major illnesses, any of which may present to the GP. Consideration must be given to identifying those who need more critical intervention and on when to transfer for higher-level of care.

Intra-urban vulnerability to heat-related mortality in New York City, 1997-2006.

The health impacts of exposure to summertime heat are a significant problem in New York City (NYC) and for many cities and are expected to increase with a warming climate. Most studies on heat-related mortality have examined risk factors at the municipal or regional scale and may have missed the intra-urban variation of vulnerability that might inform prevention strategies. We evaluated whether place-based characteristics (socioeconomic/demographic and health factors, as well as the built and biophysical environment) may be associated with greater risk of heat-related mortality for seniors during heat events in NYC. As a measure of relative vulnerability to heat, we used the natural cause mortality rate ratio among those aged 65 and over (MRR65+), comparing extremely hot days (maximum heat index 100°F+) to all warm season days, across 1997-2006 for NYC's 59 Community Districts and 42 United Hospital Fund neighborhoods. Significant positive associations were found between the MRR65+ and neighborhood-level characteristics: poverty, poor housing conditions, lower rates of access to air-conditioning, impervious land cover, surface temperatures aggregated to the area-level, and seniors' hypertension. Percent Black/African American and household poverty were strong negative predictors of seniors' air conditioning access in multivariate regression analysis.

The impact of heat waves on children's health: a systematic review.

Young children are thought to be particularly sensitive to heat waves, but relatively less research attention has been paid to this field to date. A systematic review was conducted to elucidate the relationship between heat waves and children's health. Literature published up to August 2012 were identified using the following MeSH terms and keywords: "heatwave", "heat wave", "child health", "morbidity", "hospital admission", "emergency department visit", "family practice", "primary health care", "death" and "mortality". Of the 628 publications identified, 12 met the selection criteria. The existing literature does not consistently suggest that mortality among children increases significantly during heat waves, even though infants were associated with more heat-related deaths. Exposure to heat waves in the perinatal period may pose a threat to children's health. Pediatric diseases or conditions associated with heat waves include renal disease, respiratory disease, electrolyte imbalance and fever. Future research should focus on how to develop a consistent definition of a heat wave from a children's health perspective, identifying the best measure of children's exposure to heat waves, exploring sensitive outcome measures to quantify the impact of heat waves on children, evaluating the possible impacts of heat waves on children's birth outcomes, and understanding the differences in vulnerability to heat waves among children of different ages and from different income countries. Projection of the children's disease burden caused by heat waves under climate change scenarios, and development of effective heat wave mitigation and adaptation strategies that incorporate other child protective health measures, are also strongly recommended.

A Bayesian model averaging approach for estimating the relative risk of mortality associated with heat waves in 105 U.S. cities.

Estimating the risks heat waves pose to human health is a critical part of assessing the future impact of climate change. In this article, we propose a flexible class of time series models to estimate the relative risk of mortality associated with heat waves and conduct Bayesian model averaging (BMA) to account for the multiplicity of potential models. Applying these methods to data from 105 U.S. cities for the period 1987-2005, we identify those cities having a high posterior probability of increased mortality risk during heat waves, examine the heterogeneity of the posterior distributions of mortality risk across cities, assess sensitivity of the results to the selection of prior distributions, and compare our BMA results to a model selection approach. Our results show that no single model best predicts risk across the majority of cities, and that for some cities heat-wave risk estimation is sensitive to model choice. Although model averaging leads to posterior distributions with increased variance as compared to statistical inference conditional on a model obtained through model selection, we find that the posterior mean of heat wave mortality risk is robust to accounting for model uncertainty over a broad class of models.

Heat-related illnesses during the 2003 heat wave in an emergency service.

INTRODUCTION: This study describes patients admitted to an urban emergency service in France during the 2003 heat wave. Patients with heat-related illnesses were studied and comparison was made between those who died and survivors. METHODS: A retrospective study of about 760 records concerning 726 patients aged over 65 years admitted during August 2003 to a French emergency department. RESULTS: After review of the medical records, 42 patients had heat-related illnesses. Heat-related illnesses were not diagnosed by the treating physician in any of the patients. The patients were more likely to live in institutional care and used more psychotropic medications. Hyperthermia and acute cognitive impairment were the main reasons for admission to the emergency department. The patients had a higher heart rate and body temperature and more dyspnoea and central nervous system dysfunction than those without heat-related illnesses. Twelve patients (28.6%) with heat-related illnesses died in the emergency unit or after admission to hospital. Temperature, heart rate and plasma creatinine levels were higher in those who died than in survivors with heat-related illnesses. CONCLUSION: Heat-related illnesses are a group of underestimated and underdiagnosed conditions with high morbidity and mortality rates.

[Identifying residential areas with heat-related health risks. Sociodemographic and climate data mapping as a planning tool for targeted prevention strategies]. / Wohngebiete mit hitzeabhängigen Gesundheitsrisiken ermitteln. Soziodemografische und klimatische Kartierung als Planungsinstrument gezielter Prävention.

Prognosticated heat waves in the context of climate change require appropriate strategies to prevent harmful health effects in the population. In a model project within the public health department of the Kassel region, elderly living in areas at risk of over-heating will be identified and advised. The localization of high-risk residential areas was part of the planning process. Through mapping of demographic and microclimate data and the characteristics of the material of the residential buildings, high-risk areas that require preventive measures as a top priority were identified. The prevention of heat-related mortality and morbidity by communal health authorities requires close cooperation with other administrative bodies, especially with town planning departments. Mapping demographic and microclimate data and the characteristics of the material of the residential buildings can facilitate the planning of preventive measures.

Global climate change and human health.

Global climate change is a vexing economic, environmental, and public health problem. Climatologists have documented a rise in global average temperature that is unprecedented since the Industrial Revolution. This temperature change correlates with increasing concentrations of atmospheric carbon dioxide (CO2) and other greenhouse gases, which largely are of human origin. Global climate change is likely to profoundly affect global health. This article summarizes the science of climatology and global climate change caused by human actions and reviews potential health effects.

General and specific mortality among the elderly during the 2003 heat wave in Genoa (Italy).

The effects of heat waves on health can be serious for elderly persons, especially those in urban areas. We investigated in-depth the mortality excess during the 2003 heat wave among elderly persons (>74 years) in the City of Genoa (Italy). The excess in general mortality was calculated for the period July 16-August 31, as the ratio of observed to expected deaths. To evaluate "harvesting", we compared observed and expected mortality in the period September 2003-April 2004. We also studied the relationship between mortality and climatic conditions considering daily maximum temperature and Humidex discomfort degrees, as well as "lag-time". For cause-specific mortality, we considered all pathologies reported on the death certificate. The excess in general mortality was significant and was greatest in the first half of August. During Summer 2003, in Genoa the climatic conditions (described in terms of maximum temperature and Humidex Index) were extremely hot; regarding lag-time, the greatest correlation between the number of observed deaths and the maximum temperature values was observed for the three preceding days (rho=0.568; significance level<0.01). The prominent causes of death, for which an excess was observed, were cerebrovascular diseases, severe respiratory diseases, severe renal diseases, dementia; moreover, certain pathologic conditions and symptoms, usually not lethal, were also frequent causes of death (e.g., hypovolemia, hyperpyrexia, decubitus ulcers and immobilization syndrome). The results of this study confirm the relationship between the heat waves and death among elderly, stressing that, because of their poorer physical health and the prevalence of cognitive disturbances that hinder risk perception, it is necessary to properly care for them during heat waves.

Excess deaths during the August 2003 heat wave in Paris, France.

BACKGROUND: During the August 2003 heat wave in France, almost 15,000 excess deaths were recorded. Paris was severely affected, with an excess death rate of 141%. This study had two aims: to identify individual factors associated with excess deaths during a heat wave in an urban environment and to describe the spatial distribution of deaths within the French capital. METHODS: The study population included all people who died at home between August 1st and 20th, 2003 (N=961). We identified factors associated with excess deaths by comparing the sociodemographic characteristics of the study population with those of people who died at home during the same period in reference years (2000, 2001, 2002) (N=530). Spatial differences were analysed by calculating comparative mortality rates within Paris during August 2003. Mortality ratio was determined to demonstrate temporal variations in mortality between the heat wave period and reference years. RESULTS: The major factors associated with excess death were: age over 75 years (adjusted OR=1.44 (1.10-1.90), being female (adjusted OR=1.43 (1.11-1.83)), not being married (adjusted OR=1.63 (1.23-2.15)), particularly for men. Being a foreigner appeared to be a protective factor for women. Comparative mortality rates by neighbourhood showed a gradient in excess deaths from North-West to South-East. The mortality ratio was 5.44 (5.10-5.79), with very high rates of excess death in the South (12th, 13th, 14th and 15th "arrondissement"). CONCLUSION: The August 2003 heat wave in Paris was associated with both an exceptional increase in mortality rates and changes in the characteristics of those dying and spatial distribution of mortality. Understanding the effects of a heat wave on mortality can probably be improved by an analysis of risk at two levels: individual and contextual.

Unauthorized border crossings and migrant deaths: Arizona, New Mexico, and El Paso, Texas, 2002-2003.

OBJECTIVES: We examined the major causes of and risk factors for death among migrants who died while making unauthorized border crossings into the United States from Mexico. METHODS: Decedents were included in the study if (1) their remains were found between January 1, 2002, and December 31, 2003, in any US county along the 650-mi (1040-km) section of the US-Mexican border from Yuma, Ariz, to El Paso, Tex; (2) their immigration status was unauthorized; and (3) they were believed to have died during transit from Mexico to the United States. Characteristics of the decedents and causes of and risk factors for their deaths were examined. RESULTS: Among the 409 decedents meeting our inclusion criteria, environmental heat exposure (n=250; 61.1%) was the leading cause of death, followed by vehicle crashes (n=33; 8.1%) and drownings (n=24; 5.9%). Male decedents (n= 298; 72.8%) outnumbered female decedents (n = 105; 25.6%) nearly 3 to 1. More than half of the decedents were known to be Mexican nationals (n=235; 57.5%) and were aged 20 to 39 years (n=213; 52.0%); the nationality of 148 (36.2%) decedents was undetermined. CONCLUSIONS: Deaths among migrants making unauthorized crossings of the US-Mexican border are due to causes that are largely preventable. Prevention strategies should target young Mexican men, and focus on preventing them from conceiving plans to cross the border, discouraging them from using dangerous routes as crossing points, and providing search-and-rescue teams to locate lost or injured migrant crossers.

Disparities by race in heat-related mortality in four US cities: the role of air conditioning prevalence.

Daily mortality is typically higher on hot days in urban areas, and certain population groups experience disproportionate risk. Air conditioning (AC) has been recommended to mitigate heat-related illness and death. We examined whether AC prevalence explained differing heat-related mortality effects by race. Poisson regression was used to model daily mortality in Chicago, Detroit, Minneapolis, and Pittsburgh. Predictors included natural splines of time (to control seasonal patterns); mean daily apparent temperature on the day of death, and averaged over lags 1-3; barometric pressure; day of week; and a linear term for airborne particles. Separate, city-specific models were fit to death counts stratified by race (Black or White) to derive the percent change in mortality at 29 degrees C, relative to 15 degrees C (lag 0). Next, city-specific effects were regressed on city- and race-specific AC prevalence. Combined effect estimates across all cities were calculated using inverse variance-weighted averages. Prevalence of central AC among Black households was less than half that among White households in all four cities, and deaths among Blacks were more strongly associated with hot temperatures. Central AC prevalence explained some of the differences in heat effects by race, but room-unit AC did not. Efforts to reduce disparities in heat-related mortality should consider access to AC.

Effects of temperature and ozone on daily mortality during the August 2003 heat wave in France.

During the summer of 2003, Europe experienced a heat wave that lasted almost 2 weeks in which high temperatures were accompanied by exceptionally high ozone levels. Unfortunately, few studies have examined the effects of temperature and ozone simultaneously. The authors use constrained distributed lag models to estimate the effects of daily temperature and peak ozone on mortality in 12 French cities during the heat wave and to estimate the deaths attributable to each component. Elevated minimum and maximum temperature and peak ozone all increase mortality, with substantial interaction effects between temperature and ozone. Researchers expect extreme weather events, along with elevated ozone levels and temperatures, to become more common. Our results suggest that ozone will be an important contributor to the adverse health effects of such events.

[The heat wave of August 2003: what happened?]. / La vague de chaleur d'août 2003: que s'est-il passe?

A heat wave of exceptional intensity occurred in France in August 2003, 2003 was the warmest of the last 53 years in terms of minimal, maximal and average temperatures, and in terms of duration. In addition, high temperatures and sunshine, causing the emission of pollutants, significantly increased the atmospheric ozone level. Some epidemiological studies were rapidly implemented during the month of August in order to asses the health impact of this heat wave. Excess mortality was estimated at about 14 800 additional deaths. This is equivalent to a total mortality increase of 60% between August 1st and 20th, 2003 (Inserm survey). Almost the whole country was concerned by this excess-mortality, even in locations where the number of very hot days remained low. Excess-mortality clearly increased with the duration of extreme temperatures. These studies also described the features of heat-related deaths. They showed that the death toll was at its highest among seniors and suggested that less autonomous or disabled or mentally ill people were more vulnerable. So, they provided essential information for the setting up of an early warning system in conjunction with emergency departments. The public health impact of the Summer 2003 heat wave in various European countries was also assessed. Different heat waves in term of intensity had occurred at different times in many countries with each time deaths in excess. But, it does seem that France was the most affected country. However, implementation of standardized methods of data collection through all countries is necessary to afford further comparisons. Collaborative studies will be conducted in this way. After theses first descriptive studies, further etiologic studies on risk factors and heat-related deaths were launched and are now in progress. Considering the health impact of the heat wave, national health authorities decided to launch an Heat Wave National Plan including a provisional Heat Watch Warning System (HWWS) for 2004. Developed in collaboration with Metéo France, this HWWS is based upon an analysis of historical daily mortality data and meteorological indicators in 14 French cities in order to define the best indicators and triggers. The public health impact of the heat wave of August 2003 was major. This exceptional event raises questions about anticipating phenomena which are difficult to predict. The collaborative efforts which were developed and the group of actions and studies which were implemented in a context of emergency are now useful for the setting up of early warning strategies and thus efficient prevention.

[Disorders caused by prolonged exposure to heat]. / Pathologies consécutives a une exposition prolongée a la chaleur.

France has suffered last summer an unprecedented heat wave that led to an exceptional short-term surge of mortality. Cumulative deaths between August 1st to 14th are estimated at 14,800. Epidemiological studies carried out by the Institute de Veille Sanitaire will show the circumstances and risk factors leading to heat-related pathologies. A literature review already shows the principles of prevention, the circumstances of occurrences during similar past heat waves, the risk factors and the principles of treatment. Prolonged exposure to heat can be the initial cause of death, mainly in the elderly. The subject thus dies of an overload of his natural defenses, unable to preserve his thermal homeostasis. This is then a heat shock that reaches the central nervous system. Heat shocks could kill every second patient and leads to severe neurological sequel. During a heat wave, high temperatures can also trigger or worsen other illnesses or be responsible for other so called heat-related syndromes. It is crucially important to identify subjects at risk, situations of risk, and preventive measures, knowing that heat shock leads 25% of patients to develop multi-organ failure, even when appropriately treated.