Risk of heatstroke in healthy elderly during heatwaves: A thermoregulatory modeling study

Abstract

BackgroundThe frequency of temperature extremes is rising due to global warming. During heatwaves, the older adults are more likely to experience heat-related illnesses due to impaired sweating and cardiovascular functions. Few existing studies have systematically examined the healthy elderly's survival time and heatstroke/hyperthermia prevention measures during prolonged heatwaves. ObjectivesWe aimed to systematically examine the core temperature responses of elderly during prolonged heatwaves and to predict survival time for the elderly using the modified Stolwijk thermoregulatory model. MethodsThe Stolwijk thermoregulatory model was modified to account for sweating and vasodilation alterations in the elderly during exposure to high temperatures. The model was then used to study the influence of environmental conditions on core temperature responses during the onset of classic heatstroke (Tcore = 40.5–40.6 °C) and to estimate survival time. ResultsCore temperature increases in three distinct stages under intense heat stress: an initial stage for thermoregulatory equilibrium alignment, a thermoregulatory steady-state, and a last rapid progression due to uncompensable heat stress resulting from dehydration. At the third stage, dehydration led to a fatal classic heatstroke. The increased air temperature and relative humidity shortened the survival duration. ConclusionsThe extended thermoregulation model was able to predict the core temperature responses of healthy elderly individuals exposed to extreme heat with reasonable accuracy (±0.3 °C). Furthermore, the model can be used to predict survival time and aid in the selection of efficient heatstroke prevention measures suited to the elderly.