Review and special article
Minimization of Heatwave Morbidity and Mortality

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Abstract

Global climate change is projected to increase the frequency and duration of periods of extremely high temperatures. Both the general populace and public health authorities often underestimate the impact of high temperatures on human health. To highlight the vulnerable populations and illustrate approaches to minimization of health impacts of extreme heat, the authors reviewed the studies of heat-related morbidity and mortality for high-risk populations in the U.S. and Europe from 1958 to 2012.

Heat exposure not only can cause heat exhaustion and heat stroke but also can exacerbate a wide range of medical conditions. Vulnerable populations, such as older adults; children; outdoor laborers; some racial and ethnic subgroups (particularly those with low SES); people with chronic diseases; and those who are socially or geographically isolated, have increased morbidity and mortality during extreme heat. In addition to ambient temperature, heat-related health hazards are exacerbated by air pollution, high humidity, and lack of air-conditioning. Consequently, a comprehensive approach to minimize the health effects of extreme heat is required and must address educating the public of the risks and optimizing heatwave response plans, which include improving access to environmentally controlled public havens, adaptation of social services to address the challenges required during extreme heat, and consistent monitoring of morbidity and mortality during periods of extreme temperatures.

Introduction

Periods of extremely high ambient temperatures (commonly referred to as heat waves) are associated with increases in both morbidity and mortality, especially among vulnerable populations such as older adults, children, and people with certain chronic diseases.1, 2, 3, 4 An appropriate and effective public health response must address and coordinate multiple components including local health services, social and cultural characteristics, and availability of human and financial resources to minimize the impact of extreme heat on the populace.4

Although heat waves have occasionally created substantial public health challenges, global climate changes are projected to increase the frequency and duration of heat waves.5 Therefore, it is timely to consider the following questions: (1) How do periods of extreme heat affect disease-specific mortality and morbidity? (2) What populations are at greater risk? and (3) What public health interventions and frameworks are currently used to address health risks and how can they be further improved? The authors reviewed published studies of the impact of extreme heat on morbidity and mortality for high-risk populations in the U.S., and several European and Canadian studies from the period 1958 to 2012, representing the analyses of data collected from 1900 to 2011.

Section snippets

Defining the Problem

The earth's average temperature increased about 0.75°C (1.36°F) between 1906 and 2005, and more warming is predicted (2°C −6°C, or 3.6°F–10.9°F) by 2100, based on the interaction of natural fluctuations in temperature (such as “hotter/colder than seasonal average” weather occurring over decades and showing the trends when viewed over the average human life span) with the anthropogenic effect on deforestation and greenhouse-gas emissions.6, 7, 8, 9, 10, 11, 12, 13 From 1949 to 1995, the

Health Effects

High heat and humidity can not only cause heat stroke but also exacerbate a wide range of medical conditions that are classified as heat-related, including heat cramps and heat exhaustion, as well as dehydration, and multiple chronic diseases that are not ICD-coded as heat-related.43 So, the accurate estimates of the true impact of heat waves on health are challenging, and often underestimated.

Assessing the Most Vulnerable

'The effects of extremely hot temperatures may quickly become life-threatening, especially for individuals who have limited access to medical care.61, 62, 63 Recent studies have identified multiple subgroups of those who are particularly vulnerable, including urban residents, outdoor laborers; some racial and ethnic subgroups (particularly those with low SES); people with chronic diseases; or those who are socially and geographically isolated.3, 4, 21, 62, 64, 65, 66

Strategies to Minimize the Impact of Extreme Heat on Public Health

More-intense, more-frequent, and longer heat waves are projected for the coming decades; therefore, public health officials need to improve their understanding of the patterns of morbidity and mortality during heat waves so they can provide accurate information and education at both the community and individual level, and develop strategies to ameliorate the impact of heat.5, 24, 35 Both local and national activities that may influence the incidence and/or magnitude of heat waves have emerged.

Conclusion

Further opportunities to respond to heat waves include developing optimal strategies to reach vulnerable populations by considering multiple factors to identify those at highest risk (at individual and community levels).126 Novel approaches are developing, such as the use of high-resolution remote-sensing technologies that enable the mapping of vegetation, land use, and thermal profiles. Through geospatial mapping, these data can be integrated with demographic profiles, income, prevalence of

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