1 Universidade do Estado do Rio de Janeiro, Instituto de Medicina Social, Rio de Janeiro, Brazil; 2 Universidade Federal do Rio de Janeiro, Instituto de Estudos em Saúde Coletiva, Brazil.
Objective: To investigate the association of the health-related quality of life (HRQoL) with Body Mass Index (BMI) trajectory over three years among Brazilian adolescents. Methods: Data from the Adolescent Nutritional Assessment Longitudinal Study (ELANA) that aimed to assess anthropometric trajectory and its associated factors in adolescents was used. Six schools, located in the metropolitan area of Rio de Janeiro were selected to participate in the study. A total of 791 students from Elementary School were followed during three consecutive years (2010, 2011 and 2012). HRQoL was evaluated using a Portuguese version of Kidscreen questionnaire, that is a 27- item self-report instrument applicable for children and adolescents aged 8 to 18 years. All items were classified on a five-point Likert scale ranging from never to always or not at all to extremely. The scores were transformed linearly to a 0–100-point scale end then categorized into tertiles. Higher scores indicate better HRQOL. The rate of change of BMI across time, according to the tertiles of the HRQoL at baseline was analyzed using the procedure GENMOD in SAS, with Gaussian distribution function and id link. Analysis were adjusted for the type of school. Results: The mean age of the study sample was 11.8 years old at baseline and 46% of the participants were girls. Overall, there was a greater change in BMI among adolescents who were in third tertile of HRQoL, compared to the first tertile (β=0.22; p-value=0.01). When the analysis were stratified by sex, this association was only significant among boys (β=0.43; p-value<0.001). Conclusions: Higher levels of HRQoL at baseline were positively associated with BMI trajectory, especially among boys. This finding suggests that for boys, HRQoL could possibly be related to body image, since most boys perceive having a physically strong body, and consequently higher BMI values, as an ideal body image.