Variance components models for physical activity with age as modifier: a comparative twin study in seven countries

Area of Science:

• Behavioral genetics
• Human genetics
• Epidemiology

Background:

• Physical activity levels are influenced by a complex interplay of genetic and environmental factors.
• The expression and impact of genetic predispositions can change throughout an individual's lifespan.
• Understanding these age-related changes is crucial for accurate genetic research.

Purpose of the Study:

• To investigate the influence of age as a modifier on the genetic and environmental contributions to physical activity.
• To examine cross-national variations in the heritability of physical activity across different age groups.
• To inform the design and interpretation of genetic association studies for physical activity.

Main Methods:

• Utilized an extended classical twin model incorporating age as a modifier variable.
• Analyzed self-reported physical activity data from a large twin sample (aged 19-50) across seven European countries and Australia.
• Applied statistical modeling to assess gene-environment interactions with age.

Main Results:

• Confirmed significant genetic influences on physical activity across all participating countries.
• Observed an age-related decline in heritability for physical activity in four of the seven countries studied.
• Found minimal effects of shared environment, except in older Swedish twins, and noted limitations in smaller or narrower age-range samples.

Conclusions:

• Age significantly modulates the heritability of physical activity, underscoring its importance in genetic research.
• The findings suggest that genome-wide association studies may have greater power to detect genetic variants for physical activity in younger adult cohorts.
• Future research should incorporate age-specific analyses to better understand the genetic architecture of physical activity.