1Department of Community Medicine, University of Tromsø, Tromsø, Norway. 2Department of Health and Care Sciences, University of Tromsø, Tromsø, Norway. 3Department of Clinical Therapeutic Services, University hospital of Northern Norway, Tromsø, Norway.
PURPOSE:: Physical activity plays an important role in prevention of many serious diseases. In order to develop targeted strategies that encourage physical activity, knowledge of stability of physical activity levels over time is essential. The aim of this study was to examine tracking of leisure time physical activity in adults in Northern Norway over three decades. METHODS:: We followed 5 432 women and men who attended the Tromsø Study in 1979-1980, as well as repeated examinations after 7 and 28 years. Baseline age was 20-54 years (mean age 35.8). Physical activity was assessed by self-administered questionnaires. Tracking of physical activity, defined as maintenance of relative rank of physical activity level, was estimated by Spearman's correlation coefficient and by weighted Kappa statistics. Tracking in terms of predictability of later values from earlier measurements was analyzed by generalized estimating equations (GEE). RESULTS:: A higher than expected proportion of subjects maintained their physical activity level from examination I to II (58%) and III (53%). Kappa statistics showed agreement of 0.41 and 0.29, respectively. Belonging to a specific physical activity level at baseline increased the odds of belonging to the same category at later examinations (sedentary OR 3.9 (CI 3.5, 4.4), moderately active OR 2.2 (CI 2.0, 2.4), active OR 2.9 (CI 2.6, 3.3), and highly active OR 14.0 (CI 8.7, 22.5)). Being physically active in young adulthood increased the odds of being physically active later in life (moderately active OR 3.4 (CI 3.0, 3.9), active OR 5.4 (CI 4.6, 6.4), and highly active OR 13.0 (CI 7.4, 22.8)). CONCLUSION:: This study showed tracking of leisure time physical activity over 28 years in a cohort of adults.