Prevalence of nonrestorative sleep before and during the COVID-19 pandemic: based on a nationwide cross-sectional survey among Japanese in 2019 and 2022

Background: Japanese people sleep less compared to other countries around the world. Using a large nationally representative survey in 2019 and 2022, we investigated whether sleep duration and nonrestorative sleep (NRS) among Japanese people have improved or worsened due to the COVID-19 pandemic. Methods: Data were drawn from the Comprehensive Survey of Living Conditions, a nationwide cross-sectional sample based on selfadministered questionnaires. We analyzed 426,510 people in 2019 and 375,578 people in 2022 aged >= 20 living in the community. The generalized estimating equations of the multivariable Poisson regression models were used to estimate adjusted prevalence of NRS by survey year. Potential confounders included gender, age, marital status, family size, housing tenure, equivalent household expenditures, education, employment status, illness under treatment, lifestyle behaviors (i.e., smoking, drinking, dietary, and fitness habits), mental health, and sleep duration. Results: Among the study participants, 35.7% slept less than 6 hours and 20.9% had NRS. Regarding sleep duration, the prevalence of sleep duration of less than 6 hours was significantly lower in 2022 than in 2019 for both men and women. By gender and age, the prevalence of short sleep duration (<6 hours) significantly decreased for both men and women under the age of 49, but increased significantly for men aged >= 50 and women aged >= 75. Regarding NRS, the prevalence of NRS was significantly lower in 2022 than in 2019 regardless of gender and age: Prevalence among men was 21.4% in 2019 and 18.8% in 2022, and prevalence among women was 23.7% in 2019 and 21.2% in 2022. After adjustment for potential confounders, the difference between the 2022 NRS prevalence and the 2019 NRS prevalence was minus 1.64 percent point (pp) (95% confidence interval minus 1.82 pp to minus 1.46 pp, P < 0.001), showing a significant decrease in the 2022 NRS prevalence. A significant improvement of NRS was independent of the prevalence of short sleep duration, age, gender, and employment status. Conclusions: The prevalence of NRS among the general population in Japan was significantly reduced during the COVID-19 pandemic compared to before the COVID-19 pandemic. We need to monitor whether this decline continues or returns to pre-pandemic levels.