[Bidirectional association of sleep duration and sedentary time with obesity risk among junior high school students]

Objective: To explore the association of sleep duration and sedentary duration with the risk for obesity among junior high school students, and provide evidence for the development of more effective and precise intervention measures for childhood obesity. Methods: Based on the data from the Surveillance Project of Common Diseases and Health Influencing Factors in Students in Hunan Province, a baseline survey was conducted in 3 197 junior high school students in 2021, and annual follow-up was carried out in 2022 and 2023 respectively to collect the information about BMI Z score (BMIZ), sleep duration and sedentary duration of the students. Cross-lagged panel analysis was conducted to explore the bidirectional association of sleep duration and sedentary duration with the risk for obesity, and stratified analysis was carried out in terms of gender, place of residence and ethnicity. Results: A total of 3 134 students were included in this analysis, in whom 52.04% were boys, 56.96% were from urban area, 78.14% were in Han ethnic group, and the age at baseline survey was (12.49±0.40) years. The results of cross-lagged panel analysis showed that the BMIZ in 2021 was significantly negatively correlated with the sleep duration in 2022 (β=-0.030, P<0.05), while the sleep duration in 2021 was also significantly negatively correlated with the BMIZ in 2022 (β=-0.016, P<0.05). The results of stratified analysis showed that a significant negative association between BMIZ in 2021 and sleep duration in 2022 was found in boy students (β=-0.040, P<0.05), while no such association was found in girls students. A negative association between BMIZ in 2021 and sleep duration in 2022 was found in rural students (β=-0.043, P<0.05), as well as a negative association between the sleep duration in 2021 and the BMIZ in 2022 (β=-0.021, P<0.05), while a positive association was also found between sedentary duration in 2022 and BMIZ in 2023 (β=0.008, P<0.05). In urban areas, only a positive association between the BMIZ in 2021 and the sedentary duration in 2022 was found (β=0.140, P<0.05). In the Han students, the BMIZ in 2021 was significantly negatively correlated with the sleep duration in 2022 (β=-0.041, P<0.05), while the sleep duration in 2021 was also significantly negatively correlated with the BMIZ in 2022 (β=-0.023, P<0.05), meanwhile, the sleep duration in 2022 was significantly negatively correlated with the BMIZ in 2023 (β=-0.021, P<0.05). Conclusion: Bidirectional association between sleep duration and obesity was found among junior high school students.