Familial Clustering in Inactivity and Leisure Time Physical Activity. A Quantitative Genetic Analysis

Abstract

PURPOSE: To estimate familial aggregation and quantify the contribution of genetic and environmental factors in inactivity and leisure time physical activity (PA) in Portuguese families. METHODS: The sample consisted of 2375 nuclear families (parents and two offspring) with a total of 9500 subjects. Inactivity and leisure time PA were evaluated according to the Baecke et al. questionnaire, a highly reliable and valid instrument to measure different facets of PA. Phenotypes used were based on the frequency of television viewing (inactivity), walking, cycling and time spent in walking.d-1. Familial correlations were calculated with the FCOR module of SAGE software. Heritability was estimated using variance-components methods implemented in the SOLAR software. RESULTS: (1) All familial correlations (father, mother, and their different off-spring) were significantly greater than zero, ranging from 0.11 to 0.39; (2) Subjects of the same generation tended to be more similar in their inactivity and leisure PA habits than subjects of different generations. (3) When adjusting all phenotypes for significant (p<0.001) covariates such as age, sex, social-economic status and the interaction between age and sex, the proportion of phenotypic variance due to additive genetic factors was: television viewing (h2= 24.8), walking (h2= 24.2), cycling (h2= 31.4) and time spent in walking.d-1 (h2= 36.4). CONCLUSIONS: These results suggest that inactivity and leisure time PA were characterized by a significant degree of familial aggregation and genetic influences were low-to-mo derate.