Original Research Towards a Social Epidemiological Perspective on Physical Activity and Health: The Aims, Design, and Methods of the Physical Activity Longitudinal Study (PALS)
The health benefits of physical activity are substantial; however, the lifetime and environmental determinants of sedentary living are poorly understood. The purpose of this article is to outline the conceptual background and methods of the Physical Activity Longitudinal Study (PALS), a follow-up study of a population- and place-based cohort. A secondary purpose is to report on the success of follow-up procedures. Methods: A rationale for conducting a 20-y follow-up of a nationally representative population- and place-based cohort is developed based on the extant literature dealing with socio-environmental determinants of health and on current advancements in thinking about the determinants of involvement in physical activity. Then, methods of the 2002-04 PALS (n = 2511, nonresponse = 29.8%) that began with the 1981 Canada Fitness Survey are described. Descriptive data pertaining to the success of follow-up procedures are outlined. Results: There is general consensus around the relevance of examining lifetime and environmental determinants of physical activity involvement. Longitudinal data represent one source of information for disentangling the relative importance of these determinants. Examination of PALS follow-up data show that there was no selection bias for key individual- (physical activity, other lifestyle, health) and area-level (median income, housing) variables, although fewer respondents than nonrespondents smoked or were underweight at baseline. Some demo-graphic groups were under- or over-represented among the eligible cohort, but not among participants. Conclusions: The social epidemiological perspective emerging from PALS should help policymakers and public health practitioners make strides in changing socio-environmental factors to curb sedentary life-styles and promote population health.