Changes in body mass index and health related quality of life from childhood to adolescence

<b>Objective .</b> To determine longitudinal relationships between body mass index (BMI) and health-related quality of life (HRQoL) in an adolescent population sample. <br /><b>Design.</b> Data collected in 2000 and 2005 within the Health of Young Victorians longitudinal cohort study. <br /><b>Setting.</b> Originally a community sample of elementary school students in Victoria, Australia. Follow-up occurred in either secondary schools or individuals homes. <br /><b>Participants.</b> Cohort recruited in 1997 via a random sampling design from Victorian elementary schools. Originally comprising 1 943 children, 1 569 (80.8%) participated in 2000 (wave 2, 8 – 13 years) and 851 (54%) in 2005 (wave 3, 13 – 19 years). <br /><b>Main outcome measures.</b> In both waves participants and their parents completed the PedsQL, a 23-item child HRQoL measure, and BMI z-scores and status (non-overweight, overweight or obese) were calculated from measured height and weight. Associations were tested cross-sectionally and longitudinally (linear regression, adjusted for baseline values) <br /><b>Results.</b> A total of 81.6% remained in the same BMI category, while 11.4% and 7.0% moved to higher and lower categories, respectively. Cross-sectional inverse associations between lower PedsQL and higher BMI categories were similar to those for elementary school children. Wave 2 BMI strongly predicted wave 3 BMI and wave 2 PedsQL strongly predicted wave 3 PedsQL. Only parent-reported Total PedsQL score predicted higher subsequent BMI, though this effect was small. Wave 2 BMI did not predict wave 3 PedsQL.<br /><b>Conclusions.</b> This novel study confi rmed previous cross-sectional associations, but did not provide convincing evidence that<br />BMI is causally associated with falling HRQoL or vice versa across the transition from childhood to adolescence.<br />