Self-reporting versus parental reporting of physical activity in adolescents: the 11-year follow-up of the 1993 Pelotas (Brazil) birth cohort study.

The aim of this study was to verify the agreement between different approaches for estimating levels of physical activity in adolescents. One questionnaire was administered to parents and two were administered to the adolescents. This was a cross-sectional analysis of data collected in the 2004-2005 follow-up of the 1993 Pelotas (Brazil) birth cohort study. Parents or guardians answered the following question: "Compared to most children the same age, would you say that your child exercises more, less, or the same amount?" A similar question was addressed to adolescents, as was a detailed questionnaire on physical activity. Agreement between the questionnaires was measured by the weighted kappa statistic. A total of 4,254 adolescents and parents/guardians answered the questionnaires. Kappa values indicated low agreement for all comparisons (kappa < 0.33 for all analyses). Measurement of physical activity in adolescents is complex, and available instruments should be validated prior to their use.