Associations of daily sedentary time with mental health and sleep quality in adolescents: analyses of interaction and moderation effects

Prolonged sedentary time and poor mental health are both associated with poorer sleep quality in adolescents, but how they interact to influence sleep quality is unclear. This study examined the interaction between daily sedentary time and mental health on adolescents’ sleep quality and assessed the moderating role of mental health. This cross-sectional study recruited 10,623 adolescents from 13 schools in Shiyan City, China, from October 2023 to January 2024. Data on demographics (age, sex), daily sedentary time, sleep quality, mental health, and other related factors (e.g., father’s smoking status, mode of commuting to school) were collected via self-report questionnaires. Blood pressure was measured using standard protocols. Mental health was assessed with the validated Kessler Psychological Distress Scale, and sleep quality was assessed with the validated Pittsburgh Sleep Quality Index. Multivariate logistic regression was used to examine the associations of daily sedentary time and mental health with sleep quality, as well as the additive and multiplicative interactions between daily sedentary time and mental health on sleep quality. Subsequently, the moderation of the daily sedentary time–sleep quality relationship by mental health was assessed. The prevalence of poor sleep quality was 40.14%. Adolescents with ≥ 10 h of daily sedentary time had a higher risk of poor sleep quality (OR = 1.308, 95% CI: 1.169–1.465) than those with < 10 h. Those with poor mental health had a significantly elevated risk (OR = 7.434, 95% CI: 6.535–8.456) compared to those with good mental health. A multiplicative interaction was observed between daily sedentary time and mental health on adolescents’ sleep quality (p < 0.05, OR = 0.791, 95% CI: 0.651–0.961), but no additive interaction (RERI = − 0.052, 95% CI: −4.033–3.930; AP = − 0.007, 95% CI : −0.526 − 0.512; S = 0.992, 95% CI : 0.549–1.794). Mental health levels moderated the relationship between daily sedentary time and sleep quality. Daily sedentary time and mental health were independently associated with sleep quality, and mental health moderated this relationship. These findings suggest that strategies targeting both factors may hold potential for improving adolescent sleep.