Intergenerational and genetic influences on physical activity: family data from the HUNT study, Norway.

Objectives: The objectives of this study are to examine the association of physical activity in parents with physical activity in their adult offspring and explore if the offspring's genetic liability (ie, polygenic risk score) to physical activity influences this association.

Methods: The Trøndelag Health Study cohort is a population-based longitudinal study with data collected in 1984-1986, 1995-1997, 2006-2008 and 2017-2019. We calculated the odds ratio for being physically active and mean difference in physical activity levels according to parental physical activity (device-measured and self-reported) and own polygenic risk score.

Results: Compared with offspring with mothers in the lowest third of metabolic equivalent of task (MET)-min/day accumulated by vigorous physical activities, offspring with mothers in the upper third had an OR of 1.93 (95% CI 1.65 to 2.27) for accumulating ≥900 MET-min/week of vigorous physical activity. The OR for the corresponding father-offspring association was 1.78 (95% CI 1.48 to 2.14). Compared with offspring of parents not accumulating ≥900 MET-min/week, we found an OR of 1.89 (95% CI 1.45 to 2.44) for offspring to meet the same threshold if both parents accumulated ≥900 MET-min/week. Offspring with higher polygenic risk score to bephysically active and having physically active parents did more weekly physical activity, but we found no strong evidence of multiplicative synergistic effects between these two factors (all p values ≥0.01).

Conclusion: Both parental physical activity and offspring's polygenic risk score were positively associated with physical activity levels in the adult offspring, but there was no evidence of effect modification between these factors. A family-based approach to promote physical activity may be effective from a public health perspective.