Seasonal and daily variation in indoor light and temperature are associated with sleep disturbance in dementia

Abstract

Mechanisms regulating human sleep and physiology have evolved in response to rhythmic variation in environmental variables driven by the Earth's rotation around its axis and the Sun. To what extent these mechanisms are operable in vulnerable people who are primarily exposed to the indoor environment remains unknown. We analyzed 26 523 days of data from outdoor and indoor environmental sensors and a contactless behavior-and-physiology sensor tracking bed occupancy, heart, and breathing rate in 70 people living with dementia. Indoor light and temperature, sleep timing, duration, and fragmentation, as well as the timing of the heart rate minimum, all varied across seasons. Beyond the effects of season, higher bedroom temperature and less bright indoor daytime light are associated with more disrupted sleep and higher respiratory rate. This sensitivity of sleep and physiology to ecologically relevant variations in indoor environmental variables implies that implementing approaches to control indoor light and temperature can improve sleep.