Relationship between long work hours and self-reported sleep disorders of non-shift daytime wage workers in South Korea: data from the 5th Korean Working Conditions Survey

Background: Studies have investigated the relationship between long work hours and sleep disorders; however, they have focused on shift workers or specific workers who are at high risk of industrial accidents rather than wage workers in general. The purpose of this study is to investigate the effects of long work hours on sleep disorders among non-shift daytime wage workers. Methods: We conducted a secondary analysis of data from the 5th Korean Working Conditions Survey. From the 50,205 total participants, we included 26,522 non-shift daytime wage workers after excluding self-employed people, business owners, unpaid family employees, and wage workers who work nights and shifts. Sleep disorders were categorized into "difficulty in falling asleep," "frequent waking," and "waking up with fatigue." Logistic regression analysis was used to evaluate the influence of long work hours on sleep disorders, and the odds ratios (ORs) were calculated. Results: The OR of working > 52 hours per week was 1.183 (95% confidence interval [CI]: 1.002-1.394) for the risk of developing insomnia compared with working <= 40 hours per week. The OR of waking up with fatigue was 1.531 (95% CI: 1.302-1.801). Long work hours showed no significant relationship with difficulty in falling asleep or with frequent waking. Conclusions: Working for extended hours was associated with increased fatigue upon waking in non-shift daytime wage workers.