![]() Reviews have shown that the total impact of a heat wave event will be dependent on a number of factors including heat wave magnitude, timing in season, population experience of heat wave events, and public health responses ( 47). ![]() The estimated number of deaths therefore depend on the definition of the heat episode. The excess mortality attributed to a heat wave event is the short-term increase in the numbers of deaths ( Figure 1, see color insert), a peak in mortality similar to that seen for very severe pollution episodes. Major heat wave events are also associated with other health hazards such as air pollution episodes, wild fires, and water and electricity supply failures, which also have implications for public health action. Table 1 lists the heat wave events in Europe that have been reported in the health literature. Unfortunately, best practice guidelines had not been developed in Europe or the United States until recently. Heat waves, in terms of a disaster or emergency, i.e., that involve some aspect of the overwhelming of public services, are rare. In practice, the term heat wave is applied to a wide range of meteorological conditions, from moderate to severe. What constitutes a heat wave event is loosely defined, and national weather services ( NWS) have developed their own definitions on a national or local basis. Midwest region, particularly the 1995 Chicago event ( 46). Other well-studied heat waves include several in the U.S. A major heat wave in Athens in 1987 was associated with more than 2000 deaths ( 39). The heat wave in France in August 2003 caused 14,802 deaths in a 20-day period ( 33). This review focuses on the prevention of heat-related impacts in community settings. Heat wave events and attributed mortality in Europe (adapted from Reference 52) HEAT WAVES AND THEIR IMPACTS ON HEALTH In survivors, the permanent damage to organ systems ( 17) can cause severe functional impairment ( 16) and increase the risk of early mortality ( 97). Heat stroke has a substantial case-mortality ratio, and progression to death can be very rapid (within hours). Severe heat stroke occurs when the core body temperature exceeds 103☏ and leads to multiple organ dysfunction. High temperatures cause the clinical syndromes of heat stroke, heat exhaustion, heat syncope, and heat cramps ( 42). The physiological effects of heat are reviewed extensively elsewhere, but there is a lack of evidence on heat tolerance in women, in the elderly, and in persons with chronic disease (see below). Experimental data have been used to describe a wide range of thermal indices (more than 300) ( 79) and for setting important occupational and other standards to limit exposure to heat and the associated health effects ( 77). The body can increase radiant, convective, and evaporative heat loss by vasodilatation and perspiration ( 43). Healthy adult persons have efficient heat regulatory mechanisms, which cope with increases in temperature up to a particular threshold. However, although more is known about who is most vulnerable to heat waves, there is very limited evidence on the most effective ways to prevent heat-related mortality, particularly in community settings. ![]() The relatively rapid development of these systems is a success of public health. Since the 2003 heat wave, most countries in Western Europe have implemented some public health measures for heat waves, mostly in the form of heat health warning systems ( HHWS). This topic has become a rapidly growing area of epidemiological research. This article reviews the current epidemiological information on the impacts of heat waves and hot weather and the implications for public health. The tolerance range of an individual is usually much less than this and will narrow with age or illness. Most homes have an indoor temperature of 63☏ to 87☏, and people do not comfortably live in temperatures outside this range. However, human capacity to adapt to varied climates and environments is considerable. ![]() There are clear and absolute limits to the amount of heat exposure an individual can tolerate. Human populations are acclimatized to their local climates, in physiological, behavioral, and cultural terms. Further, one of the more certain impacts of future anthropogenic climate change will be an increase in heat waves in many populations, and such heat waves will be more intense ( 35). Episodes of extreme temperature can have significant impacts on health and present a challenge for public health and civil protection services. Heat is a natural hazard, and much is known about the effects of high temperatures on the human body.
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