Objective To investigate the longitudinal relationship between sleep duration(SD)and positive youth development(PYD)among primary and secondary school students in Chengdu city using a cross-lagged model,and to provide scientific evidence for enhancing sleep management practices for students.Methods A total of 4061 students of grades 3 through 9 from the Chengdu Child Positive Development Cohort were included in this three-wave longitudinal study.There was a one-year interval between one survey and the following round of survey,and the time points for the baseline,12-month follow-up,and 24-month follow-up surveys were designated T0,T1,and T2.The PYD of the participants was assessed using the Chinese version of the Positive Youth Development Scale.The demographic data and the average daily SD over the past month were collected.Spearman correlation analysis was performed to examine the associations between SD and PYD,and a cross-lagged model was used to investigate the longitudinal relationship between them.Results The average daily SD for the 3 rounds of surveys conducted at T0,T1,and T2 was 9.00(8.04,10.00)hours,10.44(9.67,11.11)hours,and 10.39(9.83,11.00)hours,respectively,while the PYD scores were 5.30(4.73,5.71),5.27(4.73,5.73),and 5.39(4.89,5.77),respectively.Statistical significance was found in the differences of SD and PYD scores across the 3 rounds(P＜0.05).Spearman correlation analysis revealed synchronous correlations between SD and PYD at all three time points(r=0.10 at T0,r=0.18 at T1,and r=0.21 at T2,P＜0.05)and significant lagged correlations(e.g.,r=0.10 for T1-PYD and T2-SD,and likewise,significant correlation was found for the 3 other cross-lagged paths).The cross-lagged model demonstrated that PYD at T0 and T1 positively predicted SD at T1 and T2,respectively(β0-1=0.116[95％CI,0.083-0.150],β1-2=0.097(95％CI,0.067-0.127),P＜0.05),and that SD at T0 and T1 also positively predicted PYD at T1 and T2(β0-1=0.028[95％CI,0-0.056],β1-2=0.042[95％CI,0.010-0.074],P＜0.05).According to these findings,a bidirectional predictive relationship between SD and PYD across different time points was observed in primary and secondary school students.Furthermore,PYD demonstrated better performance for predicting SD than SD did for PYD.Subgroup analysis by sex confirmed the robustness of the predictive power of PYD for SD.Conclusion This study reveals a positive bidirectional predictive relationship between SD and PYD among primary and secondary school students,suggesting that higher levels of PYD may contribute to adequate sleep.These findings provide critical scientific evidence for schools and families to strengthen sleep management and promote the holistic development and well-being of adolescents.

Objective To investigate the status of work fatigue of the disabled and the healthy so that we get to know their employment quality and compressive strength, and then provide the theory basis for the national policy formulation and vocational rehabilitation. Methods We randomly investigated 280 employees (220 disabled, 60 healthy people) in 3 companies from 3 provinces with Fatigue Impact Scale (FIS). Results There was no statistically significant difference between disabled and healthy people about work fatigue, and also that of 3 domains including psycho-social, cognitive and physical activity. After comparison of 40 items on FIS，the disabled had higher fatigue than that of the healthy in 4 items which belonged to psycho-social domain (P<0.05). Conclusion Disabled people are no less than healthy people in compression capability and working capability. They should believe in themselves, and their family and the employees should have more confidence about their work capability than before. Government should provide some support with them on job retention.