Association of work-time control with sleep quality and sleep duration in South Korea

Objectives Work-time control (WTC) may influence sleep health by allowing workers to align schedules with their personal needs, but findings have been inconsistent. In South Korea, where long working hours and low autonomy are prevalent, further investigation is required. This study aimed to examine the association between WTC, sleep quality, and sleep duration in South Korean workers. Methods Cross-sectional data from the fifth wave of the Korean Work, Sleep, and Health Study, a nationwide panel survey of South Korean workers aged 19-70, were used. The analytical sample included 5183 paid employees. WTC was categorized as low or high, and sleep quality was measured by the Pittsburgh Sleep Quality Index, with poor sleep quality defined as a score ≥11. Short sleep duration was defined as <7 hours per night. Poisson regression was used to estimate the prevalence ratios (PRs) after adjusting for age, sex, education, income, occupation, working hours, and shift work. Results Low WTC was associated with a higher prevalence of poor sleep quality (PR: 1.39; 95% CI: 1.09-1.77), adjusting for age, sex, education, income, occupation, working hours, and shift work. No significant association was found between WTC and short sleep duration. In the stratified analysis of weekly working hours among employees working 40-52 hours per week, there was a significant association between low WTC and poor sleep quality. Conclusions Lower WTC was associated with poorer sleep quality. Improving work-time autonomy may enhance sleep, particularly among workers with moderate weekly working hours (40-52 hours).