Thermoregulatory responses of the elderly population.

With a significant rise in the elderly population of the developed industrialized countries due to increased life span the harmful consequences of heat and cold stresses are expected to be more notable. Although effects of these harmful stresses on morbidity and mortality of the elder population are well documented in medical reports, relatively few studies are notable for the investigation of age-related effects on thermoregulation. In this report, data on responses of older individuals to heat stress during rest and exercise are summarized. When old men (60-86 years) were exposed to 40 degrees C and 40% relative humidity for 2 hr during rest, their total body sweat rate/m2 (SR) was similar to the young group (20-35 years). The onset of sweating was also similar in both groups. Regional SR was not uniform in either age group. Since the responses of both groups were similar, data were pooled to examine the relationship between age and physical fitness, as measured by aerobic capacity (VO2 max), to physiological responses. Only VO2 max and body fat were significantly related to age. The SR was related to fitness. When old men and women walked at a level costing 40% of their VO2 max in desert heat for 1 hr, total SR was similar in all age groups. The efficiency of walking was similar in young and old, but the least fit individuals were less efficient. In all our studies, the data clearly indicate that age per se does not decrease the functional capacity of the sweating mechanism and that problems encountered by the elderly in hot environments are primarily related to impairment of the cardiovascular functions.