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Physical Activity and Academic Performance: Genetic and Environmental Associations.

INTRODUCTION
Physical activity and academic performance are believed to be associated. Though both traits are partially heritable, it remains unclear whether these traits also share a genetic and/or environmental background in common. We aimed to examine to what extent leisure-time physical activity and academic performance share genetic and environmental effects from early adolescence to young adulthood.


METHODS
Participants were Finnish twins (2543-2693 individuals/study wave) who reported their leisure-time physical activity at ages 12, 14, 17 and 24. Academic performance was assessed with teacher-reported grade point averages at ages 12 and 14 and by self-reported educational levels at ages 17 and 24. Bivariate quantitative genetic modeling at each age and between different ages was performed to decompose the trait correlation between academic performance and physical activity into genetic and environmental components.


RESULTS
The trait correlations between leisure-time physical activity and academic performance were positive, but modest at most (rtrait=0.08-0.22 in males, and 0.07-0.18 in females). The genetic correlations between leisure-time physical activity and academic performance were higher than the trait correlations (rA=0.17-0.43 in males, and 0.15-0.25 in females). Common genetic influences explained 43-100% of the trait correlations. Environmental influences shared by co-twins between leisure-time physical activity and academic performance were also correlated (rC=0.27-0.54 in males, and 0.21-0.69 in females) explaining 41-100% of the trait correlations. Unique environmental influences were correlated only in females (rE=0.10-0.15).


CONCLUSION
Both common genetic background and shared family environment (i.e., familial background) partially account for the associations observed between leisure-time physical activity and academic performance. However, the estimates vary in magnitude by age.