A review on thermal characteristics of the elderly and methods for maintaining their thermal comfort in cold winter season

The elderly tend to be influenced more by environmental coldness than the young, due to the declined thermoregulation ability with aging. Thermal comfort and health of the elderly in the cold winter season is a widely discussed topic, especially in recent aging society. To realize the mechanism of thermal responses of the elderly and figure out the state-of-the-art methods for maintaining their thermal comfort in cold environments, this study presented a thorough review on related articles. Three aspects, i.e., thermal characteristics, thermal response models, and behavioral adjustments of elderly in cold winter are discussed. It was found aging affects thermal responses via affecting body constructions, like neurons, skin thickness and vessel elasticity, etc. The elderly show lower skin and core temperatures than the young due to lower metabolism and weaker muscular and vasomotion regulation abilities; however, they show greater tolerance to coldness. A few thermoregulation models have been built to reveal the special physiological mechanism for the elderly, but they still need improvements by correcting set-point temperatures, basal blood rates, regulated heat, heat transfer coefficients and clothing thermal insulation (Icl) just according to characteristics of the elderly. Thermal sensation models also need improvements through more accurate skin temperature predictions by the optimized thermoregulation models. The two predominant adjusting methods of garment and air temperature demonstrated great differences among elderly in various regions. It is proposed that instead of overall Icl of clothing, local Icl should be made clear to guarantee local thermal comfort. Through this review of over a hundred publications across the world, the current circumstance of elderly thermal comfort in the cold winter season is clear and future research directions are proposed. This is conducive to improving the thermal comfort and health of this vulnerable sub-population in extreme weather conditions.