Age-Related changes in thermoreception and thermoregulation

This chapter focuses on age-related changes in temperature sensitivity and thermoregulation in humans. Core temperature is the net result of heat production and heat loss. Deviations from the optimal temperature occur for two main reasons: physical activity generates heat and environmental heat or cold affects body temperature as well. These changes need to be sensed, processed, and counteracted if necessary. Thus, the thermoregulatory system can be conceptualized as containing three parts: thermosensitive afferent pathways, neuronal integration and control systems, and descending effector pathways altering heat gain or loss. The functional anatomy and physiological mechanisms of these compartments and their alterations with aging are covered in separate sections: thermoreception; thermogenesis, heat gain, and heat retention; heat loss and reduction of heat gain; and central thermoregulatory control including circadian rhythms. Further, humans need to regulate their body temperature to survive. Most of the deaths due to hypothermia or hyperthermia occur in elderly subjects. The reason the elderly especially are at such an increased risk of thermoregulatory deficit is not a new question, yet still important and not solved. Is it because their capability to sense temperature is compromised, because their thermoregulatory capacities are limited, or because their physiology is less tolerant to extreme temperatures? This discussion also describes what is known about the changes in thermoreception and thermoregulation with increasing age.