Investigation of sleep quality under different temperatures based on subjective and physiological measurements

Abstract This study investigated sleep quality at different indoor temperatures (17°C, 20°C, and 23°C [62.6°F, 68.0°F, and 73.4°F]) via subjective and physiological methods by evaluating the thermal comfort and sleep quality before and after sleep. Electroencephalograms were also obtained, and skin temperatures were measured throughout the entire sleep cycle. The quantitative powers of each electroencephalogram frequency rhythm were calculated, and the duration of every sleep stage was determined. Both results show that the ambient temperature has a significant effect on sleep quality. The subjective results show that 20°C (68.0°F) was the most comfortable temperature for the waking state and 23°C (73.4°F) was the most satisfactory temperature for sleeping. The objective results show that at 23°C (73.4°F), the relative power of the sleep δ band was the highest, the duration of sleep onset latency was the shortest, and the slow-wave sleep was the longest. All these results were highly consistent, indicating that sleep quality was highest at 23°C (73.4°F). The higher thermal comfort temperature in sleep compared with that in the waking time may be due to the lower mean skin temperature during sleep. Acknowledgment The project is financially supported by the National Natural Science Foundation of China (No. 51108260) and the key project of National Natural Science Foundation of China (No. 50838009). The authors would like to thank the professors of the sleep area who came from the third affiliated hospital of Shanghai Jiao Tong University and provided helpful advice and suggestions. The authors also thank the PRP (Participation in Research Program) members at Shanghai Jiao Tong University and team members who stayed awake all night long for 24 days in case of abnormal events would have happened. Li Pan is PhD student. Zhiwei Lian is Professor. Li Lan is Postdoctoral Scholar.