Association of wood use in bedrooms with comfort and sleep among workers in Japan: a cross-sectional analysis of the SLeep Epidemiology Project at the University of Tsukuba (SLEPT) study

Several priority characteristics of wood that have beneficial effects on human beings have been reported. However, the advantages of wood use in bedroom interiors for sleep have not been fully evaluated. The aim of this cross-sectional epidemiological study was to evaluate the association of wood use in housing and bedrooms with comfort in the bedroom and sleep among workers in Japan. The study methods included sleep measurements using actigraphy and a self-administered questionnaire survey. In total, 671 workers (298 men and 373 women; mean age ± standard deviation: 43.3 ± 11.2 years) were included in the analysis. The amount of wood used in bedrooms was significantly associated with comfort in bedrooms, inversely associated with suspicion of insomnia, partly inversely associated with self-rated poor sleep quality, but not associated with low sleep efficiency. On logistic regression analysis, the adjusted odds ratio (aOR) of the “large amount of wood” group relative to the “no wood” group was 3.25 [95% confidence interval (CI) 1.63–6.47] for comfort. The aOR of the “no wood” group relative to the “large amount of wood” group was 2.15 (95% CI 1.11–4.16) for suspicion of insomnia. Wood structure of housing, as well as wood use on either the floor, wall, or ceiling, were not significantly associated with comfort and sleep conditions. Our study suggested that the use of a large amount of wood used in the bedroom interior could be beneficial for comfort, sleep, and therefore, health of workers. Further studies are required to obtain generalizable results.