Association between sleep quality and physical activity according to gender and shift work

Shift work directly causes circadian disruption and reduces sleep quality. Physical activity is also associated with sleep quality. However, no study has reported the relationship between a specific level of physical activity and sleep quality. This study aimed to investigate the relationship between sleep quality and the amount of physical activity by stratifying subjects into gender and shift-work subgroups. Among those who participated in the Kangbuk Samsung Health Study in 2016-2017, data from 185,958 full-time workers were analysed. We evaluated their physical activity by metabolic equivalents (METs-min/week), sleep quality and shift work. A chi-squared test, a t test and logistic regression analysis were performed. An increase in sleep quality was found for the group with physical activity of 600-9,000 METs-min/week compared to that in the sedentary group among all subjects. In female day workers, the sleep quality of the group with 600-6,000 METs-min/week was significantly higher (odds ratio [OR], 0.760; 95% confidence interval [CI], 0.673-857) than that in the sedentary group. In male day workers, sleep quality increased when physical activity was increased up to 6,000-9,000 METs-min/week (OR, 0.760; 95% CI, 0.673-857). In female shift workers, there was no significant difference in sleep quality according to physical activity level. In male shift workers, sleep quality was better in the group with physical activity of 1,800-3,000 METs-min/week (OR, 0.826; 95% CI, 0.692-0.986) or 3,000-6,000 METs-min/week (OR, 0.771; 95% CI, 0.642-0.926). Optimal physical activity is good for sleep quality. The sleep quality of females is significantly worse than that of males in both day and shift workers.