Associations of physical activity and sedentary time with psychological distress among Japan self-defense forces personnel dispatched overseas: a prospective cohort study

Physical inactivity and sedentary time can worsen mental health; however, their relationship remains elusive, and related evidence among workers with overseas assignments is limited. Therefore, this study aimed to investigate the relationship between changes in physical activity and sedentary time and explored the subsequent risk of psychological distress among Japan Self-Defense Forces personnel. This prospective study enrolled male Japan Self-Defense Forces personnel dispatched to the Republic of Djibouti from May 2018 to June 2019. Psychological distress data were collected before and after overseas deployment. Physical activity and sedentary time data were obtained using the Global Physical Activity Questionnaire. Psychological distress was assessed using the General Health Questionnaire 30. Mixed-effects modeling was performed to test associations between psychological distress and changes in sedentary time and physical activity. The cohort comprised 334 male Japan Self-Defense Forces personnel. The prevalence of psychological distress after deployment was 12.6%. The interaction of sedentary time and time was significantly associated with a greater psychological distress risk. Psychological distress was greater when sedentary time showed a large increase than when sedentary time showed less change during deployment. A greater increase in work-related physical activity from before to during deployment was associated with decreased psychological distress. These findings suggest that a greater increase in sedentary time from before deployment to during deployment is associated with increased psychological distress after deployment. Healthcare professionals should recommend reducing sedentary time to improve mental health, especially after overseas deployments.