Associations of outdoor time, sedentary behaviour, and sleep with psychological distress in primary and secondary school students: a cross-sectional study
Previous studies have shown that outdoor activity, sedentary behavior, and sleep duration are associated with psychological distress in children and adolescents. Using an isotemporal substitution model, this study examined the simulated effects of reallocating time among these behaviors with the risk of high psychological distress and whether sex differences exist. From March 2023 to May 2023, 6132 students aged 9–19 years (mean age = 14.0 years, 48.9% males) in Anhui Province were selected. Basic information, outdoor activity, sedentary behavior, and sleep, were collected through a questionnaire survey. The Kessler Psychological Distress Scale was used to measure the psychological distress of the study subjects. The isotemporal substitution model was used to analyze the associations of outdoor activity, sedentary behavior, and sleep duration with high psychological distress, and stratified analysis was performed by gender. The results of this survey indicate that among 6,132 primary and secondary school students, the detection rate of high psychological distress was 38.57%. Compared with students without psychological distress, those with high psychological distress reported significantly less daily outdoor activity (1.24 and 1.45 h/day, respectively) and shorter sleep duration (8.5 and 9.1 h/day, respectively). They also spent significantly more time in sedentary behavior (8.02 and 7.01 h/day, respectively). Replacing 1 h per day of sedentary behavior with the same duration of outdoor activity and sleep is associated with an 18.8% ( P < 0.001) and 26.8% ( P < 0.001) reduction in the risk of high psychological distress, respectively. Replacing 1 h per day of outdoor activity or sleep with the same duration of sedentary behavior is associated with a 23.2% ( P < 0.001) and 36.6% ( P < 0.001) increase respectively in the risk of high psychological distress. After gender stratification, replacing one hour of daily sedentary behavior with equal-duration outdoor activity or sleep was associated with reduced risk of high psychological distress: 11.5% ( P = 0.011) and 28.0% ( P < 0.001) in girls, and 25.8% ( P < 0.001) and 25.6% ( P < 0.001) in boys. Replacing one hour per day of outdoor activity or sleep with sedentary behavior was associated with a 13.0% ( P = 0.010) and 38.8% ( P < 0.001) increase in girls and a 34.7% ( P < 0.001) and 34.3% ( P < 0.001) increase in boys in the risk of high psychological distress, respectively. Therefore, outdoor activity and sleep duration were negatively associated with psychological distress, while sedentary behavior was positively associated with psychological distress among children and adolescents. Reallocating time from sedentary behavior to outdoor activity or sleep was associated with a lower risk of high psychological distress among children and adolescents, with associations differing by sex.