Heat stress in older individuals and patients with common chronic diseases

Abstract

Key points• People with age over 60 years, obesity, cardiovascular disease, pulmonary disease or long-standing diabetes are at increased risk of heat-related illness during heat waves because of physiological impairments in the regulation of body core temperature in hot conditions.• A homebound lifestyle, lack of contact with other people and decreased mobility can also contribute to an increased risk of heat-related illness.• Working home air conditioners, fans, access to transportation and access to cool environments during prolonged heat events have a protective effect against heat-related illness and deaths.• Physicians should be aware of these risk factors and protective factors against heat illness, and should counsel at-risk patients accordingly.CMAJ 2009. DOI:10.1503/cmaj.081050Previously published at www.cmaj.caReview rise in body core temperature may lead to heat illness and eventually death. Exposure to the combination of external heat stress and metabolically generated heat can lead to heat-related disorders. The prevalence of heat stress symptoms increases in direct proportion to the elevation of body core temperature. The major heat-related disorders -heat cramps, heat exhaustion and heatstroke -involve various degrees of thermoregulatory failure, which occurs when a person is exposed to excessive heat or elevations in body core temperature over a prolonged period. Risk factors for heat stress AgeObservational studies have shown that people aged 60 years and older are among the worst affected by extreme heat, 3−5 with those living in institutions, confined to bed or living alone having the highest rates of illness, injury and death. 5,8,15−17 In their ecological time-series study, Fouillet and associates 2 showed that during the 2003 heat wave in Europe, mortality ratios (ratios of observed deaths to expected deaths) in France increased continuously with age, from 1.3 for people 35-74 years of age to more than 1.7 for those over the age of 75 (Figure 1). Although the greater prevalence of comorbidities and medication use in this population may be responsible for some of the heat-related deaths, laboratory-based physiological studies have indicated that the ability to sense heat 20 and to manifest appropriate behavioural (especially fluid intake) 21−26 and physiological (e.g., blood distribution, sweating) responses 27−33 during exposure to heat may be compromised in otherwise healthy older individuals.The ability to physiologically maintain body core temperature during heat stress becomes compromised with age. 27 This decrease in thermoregulatory ability can be attributed to a combination of factors, including changes in sweating, [28][29][30]34 blood flow to the skin 30,31,34,35 and cardiovascular function. 32The problem can be exacerbated by the decreases in overall physical fitness and increases in body adiposity that may accompany aging. 36 Experts have suggested that, in combination, these age-related changes in thermoregulatory and cardiovascular function can decrease the body's abilit...

An Ecological Study of the Association between Area-Level Green Space and Adult Mortality in Hong Kong

“…Diabetics may also be particularly sensitive to the adverse health effects of hot weather. Studies have shown that circulation to the skin [31] and sweating response [32] are impaired in diabetics, and hospital admissions among diabetics have been found to be more sensitive to heat wave effects [33].…”

Climate change, extreme weather events, air pollution and respiratory health in Europe

“…In these patients, it may be hypothesised that thermoregulatory responses to heat stress, particularly those involving the respiratory system, may be ineffective at dissipating excess heat, thus increasing their risk of developing heat stress conditions such as dehydration and heatstroke. However, this hypothesis is still not supported by experimental studies [113]. A different pathway linking heat exposure to respiratory health outcomes involves the clinical course of heatrelated illnesses such as heatstroke.…”

Respiratory Effects of Indoor Heat and the Interaction with Air Pollution in Chronic Obstructive Pulmonary Disease

“…Although the mechanisms of health effects in COPD remain incompletely understood, proposed mechanisms include both thermoregulatory responses (35) and bronchoconstrictive effects of heat.…”