Determinants of physical inactivity among urban adolescents

To investigate determinants of physical inactivity among adolescents aged 15 to 19 years in the city of Recife, northeastern Brazil.

This case-control study involved 597 private school students aged 15 to 19 years selected by convenience sampling. Exclusion criteria were adolescents with diseases that interfered with or hindered anthropometric measurements, who were being treated with drugs or diet for excess weight or who had changed their physical activity over the past 30 days. The students were recruited according to physical activity, as determined by the International Physical Activity Questionnaire: cases - inactive (sedentary or insufficiently active); and controls - active (active and very active). The adolescents reported the number of hours per day of television watching and computer use to identify the number of sedentary hours/day. Anthropometry (weight and height) of the adolescents was measured by Gibson's technique and used to calculate the body mass index. Weight, height and educational level of mothers were self-reported. Data were analyzed by multiple logistic regression, using the SPSS software, version 11.5, in order to control for confounding variables.

Female adolescents were twice as likely to be inactive (odds ratio = 1.94; 95% confidence interval = 1.35-2.79) compared to male adolescents. Watching television for more than 1 hour/day showed increased risk for physical inactivity compared to less than 1 hour/day (odds ratio = 1.55; 95% confidence interval = 1.01-2.39).

Physical inactivity among adolescents was associated with females and longer time spent per day watching television.