Computational protocol: Decline in physical activity during adolescence is not associated with changes in mental health

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Protocol publication

[…] The Statistical Package for Social Sciences (SPSS) for Windows (version 19.0; SPSS, Inc, Chicago, Illinois) was used for paired sample t tests and independent sample t tests. Structural equation modelling was performed in R [] with the package Lavaan []. The distributions of the independent and dependent variables at both baseline and follow-up were normal. The level of significance was .05 in all analyses.Associations between changes of physical activity over time and changes in depressive symptoms and self-esteem were analysed by structural equation modelling (SEM). SEM was used to simultaneously estimate various associations in the data. Not only the effects on the dependent variables were modelled, but also other relevant correlations between independent variables and covariates were incorporated into the model. The model consisted of one independent variable (∆PA) and two dependent variables (∆DS and ∆SE). Relationships were controlled for physical activity at baseline (PA_Baseline), depressive symptoms at baseline (DS_Baseline) and self-esteem at baseline (SE_Baseline), as well for covariates of sex, nationality, academic year, socioeconomic status, BMI and cardiovascular fitness.Only complete cases (N = 158) were used in the analyses. Missing data were not imputed for two reasons. We did not have a valid predictive model to be used for imputation. A naive or improper imputation method could have given biased results. Second, additional analyses of the baseline data showed no significant differences on the variables of interest between the final sample and the drop outs (for more information see section).Analyses were also conducted using moderate-to-vigorous intensity physical activity as an independent variable. Moderate-to-vigorous intensity physical activity was calculated by the total number of accelerometer steps with a cadence ≥ 100 steps/min in accordance with many studies []. These results showed no relevant differences compared to analyses using the total physical activity volume per week as an independent variable and therefore have not been published. […]

Pipeline specifications

Software tools SPSS, lavaan
Application Miscellaneous
Organisms Homo sapiens