Age effects on thermal, metabolic, and perceptual responses to acute cold exposure

Thermoregulatory accidents rank as the sixth leading cause of death among older adults. Therefore, there is an urgency to clarify the influence of age on thermoregulation. This investigation sought to evaluate the influence of age on the thermal, metabolic, and perceptual responses of healthy, physically active, old (OLD) and young (YNG) men during exposure to 12, 18, and 27 degrees C for 120 min.

There were four old (67.7 +/- 4.6 yr) and four young (26.7 +/- 3.4 yr) adult men who participated. Following a baseline period (30 min), the subjects, wearing only cotton shorts, were moved into an environmental chamber where they remained seated for 120 min or until rectal temperature (Tre) was < or = 35 degrees C. Data were collected for Tre, mean skin temperature (Tsk), oxygen consumption (Vo2), tissue insulation (I), thermal sensation (TS), and heat production (HP).

Analysis of variance demonstrated a significant (p < 0.05) time x group interaction for Tre, HP, and I, whereby Tre, HP and I were higher in the YNG vs. OLD. Also, Tsk differed between YNG and OLD with the OLD exhibiting a higher Tsk. TS did not differ, although subjects reported feeling colder with each trial.

These data suggest that there may be a differential thermoregulatory response between OLD and YNG individuals. The higher Tsk in the OLD suggests a deficit in the peripheral response leading to an increased heat loss over a protracted period of time. This heat loss may contribute to the reduction in core temperature and to the development of hypothermia in the older adult.