Prevalence of sufficient levels of physical activity in adolescents: comparison between the measure obtained using simplified and detailed questionnaires

Abstract

This study aimed was to compare the prevalence of sufficient levels of physical activity produced by a measure of the simplified questionnaire compared to a detailed questionnaire and analyze the concordances between these measures in adolescents. This is cross-sectional study with 2,859 adolescents high school students (57.8% female, 14-19 years old), from the city of João Pessoa (PB), Northeast, Brazil. Physical activity was measured by two questionnaires: a simplified instrument, containing a single question and a detailed questionnaire. Adolescents engaging in physical activity ?300 minutes/week were classified as sufficiently physically active. Agreement between the two measures was evaluated by the Kappa statistic (k) and sensitivity and specificity measures using the results of the detailed questionnaire as reference. The prevalence of adequate levels of physical activity was lower in the simplified questionnaire (20.1%; 95%CI: 18.6-21.6) compared to the detailed questionnaire (50.2%; 95%CI: 48.4-52.7). Inter-questionnaire agreement was slight (almost all with k<0.30). Sensitivity of the simplified questionnaire was low (from 26.4%, 95%CI: 22.9-30.0; to 40.9%, 95%CI: 37.0-45.0), and specificity was high (from 92.3%, 95%CI: 86.9-96.0; to 94.3%, 95%CI: 92.0-96.1). The agreement between the prevalence of sufficient levels of physical activity measured by a simplified and detailed questionnaire was low. Simplified questionnaires should be used with caution because they can underestimate the prevalence of levels of physical activity in adolescents.