Do changes in working hours increase stress in Japanese white-collar workers?

Introduction: High stress at work is associated with negative health outcomes for workers, making stress prevention a critical challenge. Overtime work is an influential stress factor. This study, therefore, aimed to longitudinally evaluate how stress increased depending on changes in working hours among Japanese white-collar workers. Methods: We targeted 3,874 participants who were full-time workers and were recognized as having low stress in a web-based cohort in 2018 (T1) and 2019 (T2). We performed univariate and multivariate logistic regression with the following variables: years of experience, years of education, medical background, income, and roommates. Results: We observed a greater increase in stress among female who worked 41-50 h per week at T1 and more than 50 hours per week at T2, and those who worked more than 50 h per week at T1 and 35-40/41-50 h per week at T2, compared to those who worked 41-50 h per week both at T1 and T2, with odds ratios (ORs) and 95% confidence intervals (95% CI) of OR = 2.09, 95% CI (1.18, 3,70); OR =1.86, 95% CI (1.14, 3.03), respectively. However, no association between change in working hours and stress was found among male. Discussion: These results show that reducing stress requires decreasing working hours as well as identifying factors that lead to high stress.