Thermal sensation and sleep quality in different combinations of indoor air temperature and bedding system conditions

Thermal factor is one of the crucial factors affecting human sleep. The purpose of this study is to explore the effects of combinations of indoor air temperature and bedding system on sleep thermal sensation and sleep quality and to provide new insights into the cognition of relationship between thermal environment and sleep quality. Sleep experiments were conducted in the climate chamber and the indoor air temperature was set as 16 °C, 18 °C, 20 °C, 22 °C, and 24 °C in five conditions. The bedding system was consistent across all temperature conditions. The sleep stage, heart rate and skin temperature of subjects were continuously monitored. Meanwhile, the quilt coverage form was recorded by an infrared thermal imager. Under different temperature conditions, although the quilts were consistent, the subjects adjusted the coverage form to get close to thermal neutrality. The difference in bedding insulation was 1.32clo between the coolest condition and warmest condition. When the bedding system and indoor temperature matched to achieve thermal neutrality, the subjects had the highest sleep efficiency and the highest deep sleep proportion. The greater the degree of deviation from thermal neutrality, the more obvious the reduction of sleep efficiency and deep sleep proportion. The tendency of subjective evaluation in ease of falling asleep, calmness of sleep and sleep satisfaction was consistent with the change of objective parameters. It was suggested that when creating sleep thermal environment, the indoor temperature should not be considered as the single key parameter, the suitable matching of indoor temperature and bedding system should be pursued.