Seasonal differences in physiological and psychological responses to hot and cold environments in the elderly and young males

Oral and skin temperatures, blood pressure, heart rate, thermal sensation, and the comfort of seven healthy elderly and seven healthy young males were measured in order to evaluate the difference in thermoregulation with aging in summer and winter by exposure to relatively mild hot and cold environments. The subjects, who wore T-shirts and short pants, and were exposed to three different thermal conditions (20, 28, and 36 degrees C) for 90 min, including sitting at rest for 50 min and a head-up-tilt test for 40 min (supine (0 degrees): 25 min, upright (80): 15 min). The oral temperature in the cold was significantly lower in the summer than in the winter in both groups. The oral temperature of the elderly subjects significantly declined from that of the young subjects after 30 min in winter, and also before 30 min and after 60 min in summer. The systolic blood pressure (SBP) of the elderly subjects was significantly decreased by the head-up-tilt test in all conditions, but this was not the case in the young subjects. The reduction in SBP in the elderly subjects was significantly greater in the summer than in the winter. The elderly subjects were subjected to higher thermal and cardiovascular stresses by cold in summer and by heat in winter than the young, and their core temperature changed more widely. We found that their thermoregulatory responses were delayed, which was caused by the degradation of the vascular regulation ability with aging.