Weekday-to-Weekend Sleep Differences and Poor Mental Health in Young Adulthood

Background: We aimed to investigate associations between weekday-to-weekend sleep differences and mental health and examine whether the association varies by weekday sleep duration among young adults in South Korea. Methods: We used the Survey of Korean Youths’ Lives, a nationally representative data for young adults aged 19–34 years in South Korea. Weekday-to-weekend sleep differences were calculated by the difference between sleep durations on weekends (or free days) and those on weekdays (or working days). Indicators of mental health included unhappiness, life dissatisfaction, burnout, depression, and suicide ideation. A logistic regression analysis was conducted to investigate associations between weekday-to-weekend sleep differences and mental health. We stratified respondents by weekday sleep duration (i.e., < 7 hours and ≥ 7 hours) and examined the difference in associations of weekday-to-weekend sleep differences with mental health. Results: Among the 14,931 respondents, 49.4% and 17.1% reported having 1–2 hours and more than 2 hours more sleep during weekends compared to their weekday sleep, respectively. Moreover, 38.5% of respondents had less than the recommended hours (≥ 7 hours) of sleep on weekdays and they were more likely to have additional hours of sleep on weekends. Larger weekday-to-weekend sleep differences were associated with poor mental health. Specifically, young adults who slept more than two additional hours on weekends were more likely to experience poor mental health conditions, including unhappiness, life dissatisfaction, burnout, depression, and suicide ideation. Furthermore, the associations between weekday-to-weekend sleep differences and poor mental health were more pronounced among those who slept less than the recommended hours on weekdays. Conclusion: This study suggests that large differences in sleep duration between weekdays and weekends could be a useful indicator for detecting poor mental health status. However, further research is needed to better understand the mechanisms underlying factors contributing to weekday-to-weekend sleep differences among young adults.