Thermoregulatory and cardiovascular responses in the elderly towards a broad range of gradual air temperature changes.

Abstract

This study aimed to determine age-related differences in thermoregulatory and cardiovascular responses to a wide range of gradual ambient temperature (Ta) changes. Morphologically matched normotensive elderly and young males participated. The participants wearing only shorts rested during the 3-h experiment. After 30min of baseline at 28°C, Ta increased linearly to 43°C in 30min (warming) and then gradually decreased to 13°C in 60min (cooling). Ta was rewarmed to 28°C in 30min (rewarming), and that temperature was maintained for an additional 30min (second baseline). During the warming phase, there were no age-related differences in blood pressure (BP) and rectal temperature (Tre), despite a significantly lower cutaneous vascular conductance and heart rate in the elderly (P<0.05). At the end of the cooling phase, systolic blood pressure (SBP) in the elderly was significantly higher than the young (155.8±16.1 and 125.0±12.5mmHg, P<0.01). There was a consistent age group difference in SBP during rewarming. Mean skin temperature was significantly lower in the elderly during rewarming (P<0.05). Tre decreased more in the elderly and was significantly lower at the end of the experiment than the younger participants (36.78±0.34 and 37.01±0.15°C, P<0.05). However, there were no age group differences in thermal sensation. In conclusion, even normotensive elderly participants have a greater and more persistent BP response to cold than younger adults, suggesting that the elderly might be at a higher risk of cardiac events during cooling and subsequent rewarming.