Abstract
Objective. To determine longitudinal relationships between body mass index (BMI) and health-related quality of life (HRQoL) in an adolescent population sample. Design. Data collected in 2000 and 2005 within the Health of Young Victorians longitudinal cohort study. Setting. Originally a community sample of elementary school students in Victoria, Australia. Follow-up occurred in either secondary schools or individuals homes. Participants. 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). Main outcome measures. 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) Results. 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. Conclusions. This novel study confirmed previous cross-sectional associations, but did not provide convincing evidence that BMI is causally associated with falling HRQoL or vice versa across the transition from childhood to adolescence.
Acknowledgements
This study was supported by grants from the National Heart Foundation of Australia (NHFA), Financial Markets for Children, the Murdoch Childrens Research Institute and the National Health and Medical Research Council (NHMRC) of Australia. JW contributed to the conception, design, acquisition, analyses and interpretation of data and drafted the original article. LC contributed to the data analyses and revised the manuscript. Along with EW, MW instigated the Health of Young Victorians Study and was CIA for the third wave. She contributed to the original conception and design of this paper and its data interpretation, and undertook the final draft revision; she was supported by NHMRC Career Development Awards 284556 and 546405. KH contributed to the design, acquisition and interpretation of the data, revised the manuscript and is supported by an NHMRC/NHFA Postdoctoral Fellowship. PH contributed to the analysis plan and revision of the manuscript. EW contributed to the original conception and design of the study and interpretation of the data and revised the manuscript. GP is supported by an NHMRC Senior Principal Research Fellowship, contributed to the original conception and design of the study and interpretation of the data, and revised the manuscript. All authors have given final approval for the article to be published. We would also like to acknowledge the contribution of all field workers who conducted the data collection.
Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.