Each year, millions of people are exposed to the dangers of extreme heat. In one hot spell in London (UK) in August 2003, there was an increase in deaths of 60% among people aged over 75.[3] In England that same year, there were over 2000 excess deaths over the 10-day heatwave period compared with the previous 5 years over the same period. During a heatwave in 2009, there were approximately 300 excess summer deaths compared with similar periods in previous years.[4] As a result of climate change, it is increasingly likely that we experience extreme summer temperatures, which in turn increases the risk of heat stroke and other heat illnesses in the general population, particularly in those at risk.[4]

Urban heat islands, created in densely populated urban centres with dark rooftops, and bitumen roads tend to concentrate solar heat and prevent its dispersal. This confers a disproportionate risk of heat-related illnesses among urban dwellers.[5]

Risk factors

Older adults are at particular risk as they may be less able to recognise and respond to thermal loading.[7] Also, older people tend to have more cognitive comorbidities (e.g., dementia, Parkinson's disease) than younger people, and may take medicines (e.g., diuretics, antihypertensives) that predispose them to heat stroke.

Patients with impaired cognitive function (e.g., dementia, Parkinson's disease) may be less able to recognise and respond to thermal loading.[7]

Less able to recognise and respond to thermal loading.[7]

May predispose patients to heat stroke; these may include diuretics, beta-blockers, anticholinergics, antidepressants, antihistamines, or antipsychotics.[2]

People who are not acclimatised to hot environments are at higher risk of heat illness.[2][7] Acclimatisation reduces risk of heat stroke by making compensatory mechanisms more efficient at dissipating heat.

Increases the risk of heat illness.[2]

People who are obese are at increased risk of heat illness.[2]

A sedentary lifestyle increases the risk of heat illness.[2]

Environmental factors such as absence of adequate breaks, absence of shelter or shade, high humidity, high temperatures, or lack of access to water increase the risk of heat illness.[2]

Intrinsic and extrinsic factors can compromise the body's ability to dissipate heat and maintain homoeostasis.[2]

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