Date Published: April 18, 2019
Publisher: Public Library of Science
Author(s): Masahiro Suzuki, Tetsuya Taniguchi, Ryuji Furihata, Katsushi Yoshita, Yusuke Arai, Nobuo Yoshiike, Makoto Uchiyama, Stephany Fulda.
A scientific understanding of the effects of seasonal changes on sleep duration and sleep problems such as insomnia and hypersomnia has yet to be elucidated; however, such an understanding could aid the establishment of an optimal sleep hygiene program to treat such problems.
We investigated the effects of seasonal changes on sleep duration and sleep problems in Japanese community residents. Data on 1,388 individuals aged 15–89 years who participated in the Survey of Seasonal Variations in Food Intakes conducted by the National Institute of Health and Nutrition of Japan (2004–2007) were analyzed. Participants completed a questionnaire including items on sleep duration and sleep problems (difficulty initiating sleep [DIS], difficulty maintaining sleep [DMS]/early morning awakening [EMA], and excessive daytime sleepiness [EDS]). Data were prospectively collected at four time points (spring, summer, fall, and winter).
Seasonal changes in sleep duration were found, with the longest in winter and the shortest in summer (winter–summer difference: 0.19 h). The seasonality of sleep duration was influenced by age, sex, and residential area. In terms of age, seasonal changes in sleep duration were found in the middle and old age groups, but not in the young age group. Seasonal changes in the frequencies of sleep problems were found for some items in the young age group (DMS/EMA and EDS) and middle age group (DIS and DMS/EMA); however, no such changes were observed in the old age group.
Seasonal effects on sleep and sleep problems were found in Japanese community residents, but these varied between age groups. Furthermore, seasonal changes in sleep duration were influenced by sex and residential area.
Sleep is essential for recovery and restoration of the body and brain in humans, and a lack of sleep is associated with poor physical and mental performance . Over the last few decades, there has been growing evidence to suggest that not only short, but also long sleep is associated with adverse health outcomes, including type 2 diabetes , hypertension , cardiovascular disease , obesity , respiratory disorders , depression , and total mortality [8, 9]. Accordingly, a wide range of studies on sleep and sleep disorders has been actively carried out with respect to a variety of health statuses.
Of 1,568 participants who responded to the questionnaire at all four survey points, 180 were excluded because of missing data on one or more of the variables in the analysis (i.e., sex, sleep duration, DIS, DMS/EMA, or EDS). Therefore, the final sample used in the analyses comprised 1,388 participants. The participants’ background characteristics are shown in Table 1.
In the present study, we documented seasonal changes in sleep duration and sleep problems by prospectively assessing data collected at four time points (spring, summer, fall, and winter) in the general Japanese population. To our knowledge, this is the first prospective study on the seasonality of sleep duration and sleep problems in a general population living in a temperate region.
In the present study, seasonal effects on sleep and sleep problem were found in Japanese community residents, but the effects between age groups varied. Furthermore, seasonal changes in sleep duration were found to be influenced by sex and residential area.