[Association between sleep duration and blood pressure in school-age children: a cohort study]

Objective: To investigate the association between sleep duration and blood pressure levels in school-aged children. Methods: A prospective cohort study was conclucted. The subjects were from the healthy children cohort in western China from 2021 to 2024. The baseline survey was conducted in 2021 in Shimian County, Sichuan Province, and Jiulongpo District Chongqing; in 2022 in Jiulongpo District, Chongqing; and in 2023 in Xishui County, Guizhou Province. Follow-up surveys were carried out in 2023 and 2024. A total of 15 662 participant-visits were finally included in the analysis. Among these, the baseline included 2 716 participants in 2021, 2 766 in 2022, and 1 977 in 2023. The first follow-up included 3 831 participants in 2023 and 2 058 in 2024, while the second follow-up comprised 2 314 participants in 2024. This study collected data on demographic characteristics, lifestyle factors, and sleep status. Additionally, this study conducted uniform measurements of height, weight, blood pressure, and brachial-ankle pulse wave velocity. The restricted cubic spline (RCS) regression model was utilized to examine the nonlinear relationship between average sleep duration, average sleep duration difference between weekends and weekdays, and the risk of elevated blood pressure to identify cutoff values. The association of different average sleep durations and differences in average sleep duration with elevated blood pressure were analyzed using multivariate mixed-effects logistic regression models. Based on the generalized linear mixed model, this study estimated the differences in blood pressure and brachial-ankle pulse wave velocity between various average sleep duration groups and among groups with different average sleep duration differences. Results: At baseline, there were 7 459 children with an average age of (10.8±2.3) years. Among them, 3 848 were boys, accounting for 51.6% of the total. The overall prevalence rate of elevated blood pressure was 13.4% (1 003/7 459). The age, height, body mass index (BMI), physical activity, and pulse wave velocity in the group with elevated blood pressure were all significantly higher than those in the normal blood pressure group (all P<0.05). The analysis results of the RCS the regression model indicated that the cut-off value for average sleep duration was 9 h/d. When the average sleep duration was less than 9 h/d, a negative correlation was observed between the average sleep duration and the risk of elevated blood pressure (P=0.008). The difference of average sleep duration was positively correlated with an increased risk of elevated blood pressure (P=0.005), with a cut-off value of 2.5 h/d for this difference. Using the average sleep duration of <9 h/d as a reference, the group with an average sleep duration of ≥9 h/d had a decreased risk of elevated blood pressure (OR=0.86, 95%CI: 0.75-0.99). Compared with the difference in average sleep duration of <2.5 h/d, the risk of elevated blood pressure was increased in the group with ≥2.5 h/d' difference in average sleep duration (OR=1.23, 95%CI: 1.06-1.43). The systolic blood pressure, diastolic blood pressure, and pulse wave velocity were significantly lower in the group with an average sleep duration of ≥9 h/d compared to the group with <9 h/d (all P<0.05). Conversely, these parameters were significantly higher in the group with a difference in average sleep duration of ≥2.5 h/d compared to the group with <2.5 h/d difference (all P<0.05). Conclusion: Inadequate average sleep duration (<9 h/d) and poor sleep regularity (average sleep duration difference between weekends and weekdays ≥2.5 h/d) are significant risk factors for elevated blood pressure in children.