Development of dynamic feedback system to improve sleep environment by means of signal of autonomic nerve activity

2005 Fiscal Year Final Research Report Summary

• Project/Area Number: 15300201
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 一般
• Research Field: Rehabilitation science/Welfare engineering
• Research Institution: National Institute of Public Health
• Principal Investigator: SOKEJIMA Shigeru National Institute of Public Health, Department of Public Health Policy and Administration, Chief, 公衆衛生政策部・行政政策室長 (40262513)
• Co-Investigator(Kenkyū-buntansha): KAGAMIMORI Sadanobu Toyama University, Department of Welfare Promotion and Epidemiology, Faculty of Medicine, Dean, Professor, 医学部(保健医学), 学部長(教授) (20019615) ; UMENO Katsumi Toyama University, Department of System Emotional Science, Graduate School of Medicine, Assistant Professor, 医学研究科, 助手 (90086596) ; CHIN Kazuo Kyoto University, Department of Physical Therapeutics, Kyoto University Hospital, Associate Professor, 医学研究科, 助教授 (90197640) ; YAMAOKA Kazue National Institute of Public Health, Department of Technology Assessment and Biostatistics, Chief, 技術評価部, 開発技術評価室長 (50091038) ; KOBAYASHI Masako National Institute of Public Health, Department of Health Promotion and Research, Chief, 生涯保健部, 行動科学室長 (50262069)
• Project Period (FY): 2003 – 2005
• Keywords: sleep / thermal environment / autonomic nerve / parasympathetic nerve / heart rate variability / electroencephalogram / feed-back / quality of life

Research Abstract

In order to improve sleep depth and cardiac parasympathetic nerve activity while sleeping and subjective sleep quality in the morning, we undertook experiments to develop and verify a dynamic feed-back control system that signals by means of spectral analysis of RR interval variability were fed back at regular time intervals to adjust bedroom ambient temperature.
The principle of system operation tested here was based on the following three observations which were derived from a study on the effect of sequential control of bedroom temperature on the sleep depth and RR interval variability. We examined the differences of electrocardiogram or electroencephalogram between two bedroom environments with 28℃ constant and U-shaped controlled temperatures (number of subjects were 7). In the results, we observed (1) both levels of RR interval variability spectrum power of high frequency band (HF, 0.15-0.4Hz, unit : msec^2), which is known to represent cardiac parasympathetic activity while sleep ing, and of brain wave spectral power of delta band (δ, 0.5-4Hz, unit : μV^2), which is known to represent sleep depth, were depend on the room temperature, (2) HF and δ sometimes increased and decreased in the same direction when the room temperature was changed while sleeping, however, (3) the relationships between room temperature and HF or δ were suggested to differ considerably in individuals, as well as in the elapsed hours after the onset of sleep even in an individual.
With these observations, we constructed a feed-back system of ambient temperature that starts from neutral temperature (25℃), then, every 5 minutes, increases temperature by 1℃ when HF has increased, and changed temperature by same degree in the counter direction when HF has decreased. Sleep experiments with three constant room temperatures (22℃, 25℃, and 28℃) were set as control ones. To confirm the effect of the dynamic feed-back system, all these transitions of HF and δ during sleep were compared. Relative humidity has been adjusted to 50% during sleep.
When room temperature was kept constant at 22℃, 25℃, or 28℃, average HF over whole sleep was highest at 22℃ and lowest at 28℃, while average δ was highest at 28℃ and lowest at 22℃ (number of subjects were 10). When the feed-back system developed in the study was operated, both average values of HF and δ8 were higher by 10% or more than those at 25℃, although subjective sleep quality in the morning differed between the types of thermal control. The average room temperature achieved under the feed-back system was lower than 25℃. The present study showed a step toward the practical use of dynamic feed-back control system of thermal environment during sleep.