Aging and human cold tolerance.

Hypothermia is widely considered to be a more serious threat for older than for younger persons because of older person's impaired ability to defend body temperature during cold exposure. Some epidemiological studies indicate that the incidence of death from hypothermia increases with age, but surveys of body temperature normally maintained by older persons while in their own homes do not indicate a large incidence of hypothermia. More reliable comparisons of thermoregulatory responses to cold stress in younger and older subjects have been performed under controlled conditions in laboratory experiments. Generally, older men appear less able than younger men to defend their core temperature during experimental cold exposures. Cold exposure may elicit a slightly smaller rise in metabolic heat production, and the cutaneous vasoconstrictor response to cold may be less responsive in old than in young men. These aging effects may, however, be limited to men. In a recent study, older women appeared to defend core temperature during cold exposure as well as, or better than, younger women. Preventable changes in body composition and physical fitness rather than aging per se may contribute to impaired thermoregulatory responses to cold observed in older workers.