PURPOSE: Both genetic and environmental factors contribute to individual differences in physical activity. However, it remains uncertain whether the home environment can modify the effects of genetic factors on physical activity. We examined to what extent the psychosocial home environment in childhood and adolescence modifies the genetic influences on leisure-time physical activity in young adulthood by using Finnish twin data.
METHODS: Families with twins born between 1983 and 1987 took part in the population-based FinnTwin12 study. The psychosocial home environment was assessed by twins at ages 12, 14 and 17, as well as by their parents when the twins were age 12 using an 8-item questionnaire. At age 24, twins assessed their leisure-time physical activity based on a series of structured questions, which were used to calculate leisure-time MET hours per day. Data of 3,305 twins were analyzed using a gene-environment interaction model with OpenMx software.
RESULTS: Parental ratings of positive home atmosphere as well as the twins’ ratings of both positive home atmosphere at age 14 and lower relational tensions at ages 12 and 14 predicted higher leisure-time physical activity levels in young adulthood (regression coefficients 0.33-0.64). Parental perceptions as well as the twins’ perceptions of positive home atmosphere at ages 14 and 17 increased the additive genetic variation (moderation effects 0.60, 95% CI 0.26-1.05; 0.55, 95% CI 0.29-0.80 and 0.52, 95% CI 0.19-0.87, respectively). The twins’ ratings of positive home atmosphere at age 12 and lower relational tensions at ages 12 and 14 increased the unique environmental variation of their subsequent physical activity (moderation effects 0.46, 95% CI 0.19-0.60; 0.48, 95% CI 0.29-0.64 and 0.85, 95% CI 0.12-0.95, respectively).
CONCLUSION A warm and supportive psychosocial home environment in childhood and adolescence not only increases the level of leisure-time physical activity in young adulthood, but also modifies the variation of genetic and environmental influences on leisure-time physical activity. In terms of clinical implications, it would be important to find ways to help parents create a home environment that is both warm and supportive for their children because it can go a long way toward developing their offspring’s interest in physical activity.