Physical activity matters: associations among body mass index, physical activity, and health-related quality of life trajectories over 10 years.

BACKGROUND: The objective of this study was to assess the associations among body mass index (BMI), leisure time physical activity (LTPA) and health-related quality of life (HRQL) trajectories among adults. METHODS: Self-reported data were drawn from the Canadian National Population Health Survey, with respondents being interviewed every 2 years between 1996-97 and 2006-07. Using growth curve modeling, HRQL trajectories for individuals aged 18 and over were associated with measures of BMI and LTPA. Growth models were constructed separately for males and females. RESULTS: Findings suggested that, for males, BMI categories had little impact on baseline HRQL, and no impact on the rate of change in HRQL. Among women, higher BMI categories were associated with significantly lower baseline HRQL. However, BMI had no impact on the rate of change of HRQL. Conversely, for both men and women and regardless of BMI category, LTPA had significant impacts on baseline HRQL, as well as the rate of change in HRQL. Individuals who were inactive or sedentary had much steeper declines in HRQL as they aged, as compared with individuals who were active in their leisure time. CONCLUSIONS: The results underscore the importance of LTPA in shaping trajectories of HRQL.