Investigating the effect of total thermal environment and its variation on sleep

The purpose of this study was to investigate the effect of total thermal environment and its variation on sleep. Sleep is crucial for human health, and lack of sleep impacts mental performance. Of the many factors affecting sleep, thermal environment is known to play an important role, and its effect on sleep has been an active area of research for a long time. However, most studies only consider an average value of thermal environment during the night. We carried out a field survey in September and October 2013 in actual bedrooms at 16 residences. Thermal environment was monitored continuously during the subjects’ sleep sessions for 5 consecutive nights. All subjects wore an actigraph unit to monitor sleep and questionnaires were filled in before and after sleep. The results showed that an increase in air turbulence increases the probability of awakening, suggesting that variation in air velocity may cause sleep disruption. To take into account all factors of thermal environment, thermal load on body and its variation were calculated and their effects on sleep were evaluated. From these results, it was concluded that local heat stimulation and draft might be the cause of sleep disruption.