https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(14)62114-0.pdf

Mortality risk attributable to high and low ambient temperature: a multicountry observational study

Heat is an environmental and occupational hazard. The prevention of deaths in the community caused by extreme high temperatures (heat waves) is now an issue of public health concern. The risk of heat-related mortality increases with natural aging, but persons with particular social and/or physical vulnerability are also at risk. Important differences in vulnerability exist between populations, depending on climate, culture, infrastructure (housing), and other factors. Public health measures include health promotion and heat wave warning systems, but the effectiveness of acute measures in response to heat waves has not yet been formally evaluated. Climate change will increase the frequency and the intensity of heat waves, and a range of measures, including improvements to housing, management of chronic diseases, and institutional care of the elderly and the vulnerable, will need to be developed to reduce health impacts.

https://www.annualreviews.org/doi/pdf/10.1146/annurev.publhealth.29.020907.090843

Heat Stress and Public Health: A Critical Review

Cells from virtually all organisms respond to a variety of stresses by the rapid synthesis of a highly conserved set of polypeptides termed heat shock proteins (HSPs). The precise functions of HSPs are unknown, but there is considerable evidence that these stress proteins are essential for survival at both normal and elevated temperatures. HSPs also appear to play a critical role in the development of thermotolerance and protection from cellular damage associated with stresses such as ischemia, cytokines, and energy depletion. These observations suggest that HSPs play an important role in both normal cellular homeostasis and the stress response. This mini-review examines recent evidence and hypotheses suggesting that the HSPs may be important modifying factors in cellular responses to a variety of physiologically relevant conditions such as hyperthermia, exercise, oxidative stress, metabolic challenge, and aging.

https://www.physiology.org/doi/pdf/10.1152/japplphysiol.01267.2001

Invited Review: Heat shock proteins: modifying factors in physiological stress responses and acquired thermotolerance

The effect of elevated temperature on mortality is a public health threat of considerable magnitude. Every year, a large number of hospitalizations and deaths occur in association with exposure to elevated ambient temperatures (1, 2). An average of 400 deaths annually are counted as directly related to heat in the United States, with the highest death rates occurring in persons aged 65 years or more (3). The actual magnitude of heat-related mortality may be notably greater than what has been reported, since we do not have widely accepted criteria for determining heat-related death (4, 5–7), and heat may not be listed on the death certificate as causing or contributing to death. Persons living in urban environments may be at particularly increased risk for mortality from ambient heat exposure, since urban areas typically have higher heat indexes (combinations of temperature and humidity (8)) than surrounding suburban or rural areas, a phenomenon known as the “urban heat island effect” (9). Moreover, urban areas retain heat during the night more efficiently (10). Thus, as the US population becomes more urbanized and the number of elderly people continues to increase (11), the threat of heat-related mortality will probably become more severe. Many of these deaths may be preventable with adequate warning and an appropriate response to heat emergencies, but preventive efforts are complicated by the short time interval that may elapse between high temperature exposure and death. Thus, prevention programs must be based around prospective and rapid identification of high-risk conditions and persons. We carried out this review to assess the current epidemiologic evidence available for this purpose.

Relation between Elevated Ambient Temperature and Mortality: A Review of the Epidemiologic Evidence

Episodes of extremely hot or cold temperatures are associated with increased mortality. Time-series analyses show an association between temperature and mortality across a range of less extreme temperatures. In this paper, the authors describe the temperature-mortality association for 11 large eastern US cities in 1973-1994 by estimating the relative risks of mortality using log-linear regression analysis for time-series data and by exploring city characteristics associated with variations in this temperature-mortality relation. Current and recent days' temperatures were the weather components most strongly predictive of mortality, and mortality risk generally decreased as temperature increased from the coldest days to a certain threshold temperature, which varied by latitude, above which mortality risk increased as temperature increased. The authors also found a strong association of the temperature-mortality relation with latitude, with a greater effect of colder temperatures on mortality risk in more-southern cities and of warmer temperatures in more-northern cities. The percentage of households with air conditioners in the south and heaters in the north, which serve as indicators of socioeconomic status of the city population, also predicted weather-related mortality. The model developed in this analysis is potentially useful for projecting the consequences of climate-change scenarios and offering insights into susceptibility to the adverse effects of weather.

/pdf/temperature-and-mortality-in-11-cities-of-the-eastern-united-3j6fmesspy.pdf

Temperature and Mortality in 11 Cities of the Eastern United States

Background During a record-setting heat wave in Chicago in July 1995, there were at least 700 excess deaths, most of which were classified as heat-related We sought to determine who was at greatest risk for heat-related death Methods We conducted a case–control study in Chicago to identify risk factors associated with heat-related death and death from cardiovascular causes from July 14 through July 17, 1995 Beginning on July 21, we interviewed 339 relatives, neighbors, or friends of those who died and 339 controls matched to the case subjects according to neighborhood and age Results The risk of heat-related death was increased for people with known medical problems who were confined to bed (odds ratio as compared with those who were not confined to bed, 55) or who were unable to care for themselves (odds ratio, 41) Also at increased risk were those who did not leave home each day (odds ratio, 67), who lived alone (odds ratio, 23), or who lived on the top floor of a building (odds ratio, 47) Ha

https://www.nejm.org/doi/pdf/10.1056/NEJM199607113350203

C H Rubin

Papers

Heat-Related Deaths during the July 1995 Heat Wave in Chicago