Sedentary behavior is defined as any waking behavior involving an energy expenditure of 1.5 metabolic equivalents or less while in a sitting or reclining posture. Such behavior is particularly prevalent and has increased during the COVID-19 pandemic. Sedentary behavior has been associated with morbidity and mortality from various non-communicable diseases, even independent of physical inactivity. In addition, sedentary behavior is associated with an increase in the risk of mental disorders. We conducted a 1-year prospective cohort study among 233 Japanese workers without major depressive episode (MDE) and included 231 workers in the analysis. The estimated median posterior probability distribution of the HR of long sitting time was 2.11 (95% highest density interval [HDI]: 0.42-10.22) after adjustment for physical activity level and other covariates. However, the linear association indicated conflicting results. Non-linear associations between sitting time and MDE onset might explain this inconsistency. The evidence for an adverse association between sitting time at work and MDE onset remains inconclusive. Future studies with larger cohorts and greater statistical power should be conducted to confirm this association.
