Abstract
The thermal environment is one of the most important factors that can affect human sleep. The effects of thermal environment on sleep stages are strongly linked to human thermoregulation, which affects the mechanism regulating sleep. In addition, sleep behavior is ordinarily an indoor activity in which people spend about one-third of their lives. Ambient thermal environment around the human body during sleep is influenced by the outdoor climate even inside the house. Year round, people can sleep naked or clothed, with or without bedding, using air conditioners or heating blankets to make the environment comfortable for sleeping. This paper describes how the thermal environment influences human thermoregulation during sleep or sleep itself as well as the relationships between sleep and thermoregulation. Moreover, in order to establish thermally comfortable environments for sleep, the effects of humid heat on sleep and thermoregulation; how to control the air conditioner, fanning, or head cooling in summer; and the effects of cold environment and bathing on sleep in winter were reviewed from recent Japanese studies.
