Is the use of high correlated color temperature light at night related to delay of sleep timing in university students? A cross-country study in Japan and China

Journal of Physiological Anthropology

Akira Yasukouchi¹  Shigekazu Higuchi¹  Michihiro Ohashi²  Yichi Zhang²  Shingo Kitamura³  Yandan Lin⁴  Jingjing Qiu⁴  Sang-il Lee⁵ 

[1] Department of Human Science, Faculty of Design, Kyushu University, 4-9-1 Shiobaru, Minamiku, 815-8540, Fukuoka, Japan;Department of Kansei Science, Graduate School of Integrated Frontier Sciences, Kyushu University, 4-9-1 Shiobaru, Minamiku, 815-8540, Fukuoka, Japan;Department of Sleep-Wake Disorders, National Institute of Mental Health, National Center of Neurology and Psychiatry, 4-1-1, Ogawa-Higashi, Kodaira, 187-8553, Tokyo, Japan;Institute for Electric Light Sources, Fudan University, 200433, Shanghai, China;Laboratory of Environmental Ergonomics, Faculty of Engineering, Hokkaido University, Kita 8, Nishi 5, Kita-ku, 060-0808, Sapporo, Hokkaido, Japan;

关键词: Circadian rhythm;    Sleep;    Blue light;    Social jetlag;    University students;    International comparison;   

DOI  :  10.1186/s40101-021-00257-x

来源: Springer

【 摘 要 】

BackgroundBlue-enriched white light at night has the potential to delay the circadian rhythm in daily life. This study was conducted to determine whether the use of high correlated color temperature (CCT) light at home at night is associated with delay of sleep timing in university students.MethodsThe survey was conducted in 2014–2015 in 447 university students in Japan and 327 students in China. Habitual sleep timing and type of CCT light at home were investigated by using a self-administered questionnaire. The Japanese students were significantly later than the Chinese students in bedtime, wake time, and midpoint of sleep. They were asked whether the lighting in the room where they spend most of their time at night was closer to warm color (low CCT) or daylight color (high CCT). The amount of light exposure level during daily life was measured for at least 1 week by the use of a light sensor in 60 students in each country.ResultsThe percentages of participants who used high CCT lighting at night were 61.6% for Japanese students and 80.8% for Chinese students. Bedtime and sleep onset time on school days and free days were significantly later in the high CCT group than in the low CCT group in Japan. The midpoint of sleep in the high CCT group was significantly later than that in the low CCT group on free days but not on school days. On the other hand, none of the sleep measurements on school days and free days were significantly different between the high CCT and low CCT groups in China. Illuminance level of light exposure during the night was significantly higher in Japanese than in Chinese, but that in the morning was significantly higher in China than in Japan.ConclusionsThe use of high CCT light at night is associated with delay of sleep timing in Japanese university students but not in Chinese university students. The effects of light at night on sleep timing and circadian rhythm may be complicated by other lifestyle factors depending on the country.

【 授权许可】

CC BY