| ObjectivesTo describe the developmental trajectory of depressive symptoms in college students,to elucidate the independent and combined effects of problematic mobile phone use and physical inactivity on the etiology of depressive symptoms,and to compare the magnitude of their independent and combined effects on the predictive trajectory of depressive symptoms.Epigenetic indicators were used to further reveal the moderating effect of DNA methylation of biological clock genes between the independent and combined effects of problematic mobile phone use and physical inactivity at baseline and the longitudinal association of depressive symptoms at 2 years in college students.MethodsThis study was based on a cohort study of college students’ behavior and health,and the survey period was from April 2019 to May 2021.Using convenience sampling and random sampling methods,one medical university and one comprehensive university were selected in Hefei City,Anhui Province and Shangrao City,Jiangxi Province in April-May 2019,and a total of 1,179 freshmen majoring in public health,nursing,chemical and environmental,and physical education were selected to participate in the questionnaire survey in each university by major and class as sampling units,respectively,and 1,151 questionnaires were returned A total of 1,151 questionnaires were returned,and 1,135 valid questionnaires were excluded,with an effective rate of 98.6%.Electronic questionnaires were used to collect information related to college students’ behavior and mental health,including demographic information,problematic mobile phone use,physical activity level,depressive symptoms and other questions.Self-rating questionnaire for adolescent problematic mobile phone use(SQAPMPU),international physical activity questionnaire-short form(IPAQ-SF),and patient health questionnaire 9-item(PHQ-9)were used in the baseline and follow-up surveys to evaluate problematic mobile phone use,physical activity level and depressive symptoms among college students,respectively.In addition,the principle of informed consent and voluntariness was followed in the baseline survey,and participants were organized to undergo physical examination at the nearest tertiary hospital,and a total of 744 fasting blood samples were collected for DNA methylation level testing of biological clock genes,which was 645 after matching with the questionnaire database.The fourth follow-up survey was conducted in April and May2021,and 1,161 questionnaires were distributed,1,154 questionnaires were returned,47 invalid questionnaires were excluded,and 1,107 valid questionnaires were included,with an effective rate of 95.9%.The validity rate was 95.9%.The baseline database was matched with the four follow-up databases,and the final number of questionnaires included in the analysis was 999,and the number of missing persons was 136(the rate of missing persons was 12.0%).SPSS 23.0 and Mplus(version 8.0)software were used for statistical analysis of the data,and the main analysis methods included descriptive analysis,nonparametric test,binary logistic regression analysis,latent class growth modeling(LCGM),and moderating effect analysis.A binary logistic regression model was constructed to analyze the association and strength of the independent and combined effects of problematic mobile phone use and physical inactivity in the baseline survey and depressive symptoms in the baseline/follow-up survey before and after controlling for the main confounding factors(gender,parental education,health condition,and smoking and alcohol consumption),and a moderating effect analysis was conducted using the process plug-in in SPSS software to explore The moderating effect of DNA methylation levels of the biological clock gene between the independent and combined effects of problematic mobile phone use and physical inactivity at baseline and the longitudinal association of depressive symptoms at 2 years in college students.Differences were considered statistically significant at P< 0.05.ResultsIn the baseline survey,the detection rates of problematic mobile phone use and physical inactivity groups among college students were 24.6% and 14.6%,respectively,and the detection rate of depressive symptoms was 42.6%.Applying a binary logistic regression model to analyze the association between the independent and combined effects of problematic mobile phone use and physical inactivity and depressive symptoms,setting the normal behavior group as the reference,the combined effect group of problematic mobile phone use and physical inactivity(OR=7.91,95%CI:3.99-15.67)was positively associated with depressive symptoms(P<0.05),and the combined group of problematic mobile phone use and physical inactivity had a significantly greater effect on depressive symptoms than the independent effect group of problematic mobile phone use and physical inactivity.Stratified analysis by gender variable did not reveal gender differences in the association between the combined effect group of problematic mobile phone use and physical inactivity and depressive symptoms.In the 2-year follow-up survey,the trajectory of depressive symptoms among college students showed two trends: the depressive symptom enhancement group,in which depressive symptoms were generally on the rise,with 17.5% of the total sample size;and the depressive symptom reduction group,in which depressive symptoms were on a decreasing trend,with 82.5% of the total sample size.A binary logistic regression model was used to analyze the longitudinal association between the independent and combined effect of problematic mobile phone use and physical inactivity and depressive symptoms,and after controlling for confounders,the results showed that the combined effect group of problematic mobile phone use and physical inactivity(OR=2.96,95%CI:1.60-5.48)was associated with an increased risk of occurrence in the group with an enhanced trajectory of depressive symptoms over 2 years(P<0.05).In a further stratified analysis according to gender,the combined effect group of problematic mobile phone use and physical inactivity in male college students(OR=3.05,95%CI:1.17-7.94)was associated with an increased risk of occurrence in the group with an enhanced trajectory of depressive symptoms over a 2-year period.In the PROCESS moderation effect analysis only the CRY1 gene DNA methylation level was found to have a negative moderation effect(β=-427.4788,P<0.05)in the combined group of baseline problematic mobile phone use and physical inactivity in association with depressive symptoms at 2 years,while the other clock genes(ARNTL,CLOCK,CRY2,CSNK1 D,CSNK1E,NPAS2,NR1D1,PER1,PER2 and PER3)DNA methylation levels had no moderation effect.After stratified analysis by gender,a negative moderating effect of CRY1 gene DNA methylation levels was found among male college students between the combined effects of problematic mobile phone use and physical inactivity and depressive symptoms at 2 years(β =-682.9313,P < 0.05).ConclusionsThe independent and combined effects of problematic mobile phone use and physical inactivity were positively associated with depressive symptoms in college students,and the combined effect of the two on depressive symptoms was significantly higher than their independent effects,and some of the associations were gender-specific.In male college students,the combined effect of problematic mobile phone use and physical inactivity at baseline predicted depressive symptoms trajectories.In addition,biological clock genes DNA methylation levels exerted a moderating effect in the longitudinal association between the combined effects of problematic mobile phone use and physical inactivity and depressive symptoms. |
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