Abstract 12890: Heritability of Daily Physical Activity as Assessed by Combined Heart Rate and Movement Sensing in 771 Same-Sex Twin Pairs

Abstract

Background: Despite the health-promoting effects of physical activity (PA) and despite efforts to promote PA in the population, the majority of adults do not adhere to the current PA guidelines. The presence of innate, genetic factors that drive PA behavior may explain this contradiction. However, twin and family studies examining the heritability of daily PA have so far been limited by poor PA measurement quality or small sample size. Objective: To examine the heritability of daily PA using combined heart rate and movement sensing in a large population of adult twins. Methods: PA was assessed in daily life for 6.8 ± 1.2 days (mean ± SD) in 419 monozygotic and 352 dizygotic same-sex twin pairs using Actiheart (1,542 individuals aged 56.3 ± 10.3 yrs, BMI 26.0 ± 4.8 kg/m2). Actiheart provided information on trunk acceleration along the longitudinal axis of the body, representing bodily movements produced by skeletal muscles. It also provided information on PA energy expenditure (PAEE) and the time spent on sedentary, light intensity and moderate-to-vigorous intensity activities. We estimated the contribution of genetic (dominant and/or additive) and environmental (common and/or unique) factors to inter-individual variance in daily PA after adjusting for sex, age, age2 and body size (body mass for PAEE; BMI for the remaining measures) using structural equation modeling. Findings: Dominant and additive genetic factors together explain between 37% (95% CI 29% - 45%) of the variance in acceleration to 48% (95% CI 41% - 55%) of the variance in PAEE. The remaining variance is explained by unique environmental factors. Common environmental factors play at most a marginal role (0.5% - 6.4%).

Conclusion: Although environmental factors explain the largest proportion of the variance in daily PA, genetic factors also play a considerable role. Innate biological processes may thus explain inter-individual differences in adherence to the PA guidelines in adults. Such processes may relate to physical fitness, perception of ability, sensitivity to internal/external rewarding cues, physical discomfort following PA and/or triggering of food intake when using PA as a weight loss strategy. Future gene discovery studies are anticipated to increase our understanding of PA behavior.