Multivariate hierarchical model for physical inactivity among public school children.

Objective: To identify biological and sociodemographic factors associated with physical inactivity in public school children.

Methods: Parents of 2,519 children (49.3% of whom were girls), aged 7 to 10 years (mean = 7.6+/-0.9 years), from eight public schools in São Paulo, Brazil, completed a self-administered questionnaire. We used multiple correspondence analysis to identify groups of responses related to levels of physical activity and inactivity and to obtain an optimal scale. The cluster analysis identified groups of active and inactive children. The analysis of the receiver operator characteristic (ROC) curve, for the study of diagnostic properties of a simplified scale for physical inactivity derived from the optimal scale, revealed that a cutoff point of 3 had the best sensitivity and specificity, being therefore used as the outcome variable in the regression model. A multivariate hierarchical model was built, including distal and proximal categorical variables, with a p < 0.05.

Results: Physical inactivity was positively associated with biological factors such as being overweight, being older than 7.5 years, being a female, and having a good appetite, and with socioeconomic factors such as having garbage collected less than twice a week and having mothers who work outside the home.

Conclusion: The results are consistent with published data about determinant factors of physical activity and inactivity among children, showing that questionnaires answered by parents and submitted to a sophisticated statistical analysis can be used in population-based studies involving children younger than 10 years old.