Familial resemblance of physical activity levels in the Portuguese population

Objectives: Moderate to high levels of physical activity are related to positive health status. Parents share with their children important cultural aspects and beliefs related to healthy living. However, family studies show contradictory results for familial aggregation of physical activity. The purposes of this study were to assess whether physical activity shows familial aggregation in the Portuguese population and to disentangle the exact pattern of familial resemblance. Design: Cross-sectional family study. Methods: We sampled 2661 Portuguese nuclear families (10,644 subjects) and assessed their physical activity using the Baecke questionnaire, including components for physical activity work/school, leisure-time activity, sports participation, and a total index of physical activity. Generalized estimating equations were used to compute spousal, parent-offspring and sibling correlations. Results: For leisure-time activity and total index of physical activity, the patterns were characterized with spouse correlations higher than parent-offspring correlations (0.20 vs 0.12, p=0.001 and 0.22 vs 0.12, p=10^-4, respectively) but lower than those in offspring (0.20 vs 0.51, p<10^-4 and 0.22 vs 0.35, p<10^-4, respectively). For sports participation, the spouse correlation was higher than parent-offspring correlations (0.30 vs 0.18, p<10^-4), but also higher than sibling correlations (0.30 vs 0.22, p<10^-4). Finally, the physical activity work/school spouse correlation was higher than the sibling correlations (0.22 vs 0.12, p<10^-4). Conclusions: The results support the hypothesis of familial aggregation in physical activity. Further, fathers and mothers had a similar influence on their offspring's physical activity levels irrespective of their sex, and equal sibling correlations point toward shared physical activity habits.