title: Heritability of objectively assessed daily physical activity and sedentary behavior.
abstract: BACKGROUND
  Twin and family studies that estimated the heritability of daily physical activity have been limited by poor measurement quality and a small sample size.
  
  
  OBJECTIVE
  We examined the heritability of daily physical activity and sedentary behavior assessed objectively by using combined heart rate and movement sensing in a large twin study.
  
  
  METHODS
  Physical activity traits were assessed in daily life for a mean (± SD) 6.7 ± 1.1 d in 1654 twins from 420 monozygotic and 352 dizygotic same-sex twin pairs aged 56.3 ± 10.4 y with body mass index (in kg/m(2)) of 26.1 ± 4.8. We estimated the average daily movement, physical activity energy expenditure, and time spent in moderate-to-vigorous intensity physical activity and sedentary behavior from heart rate and acceleration data. We used structural equation modeling to examine the contribution of additive genetic, shared environmental, and unique environmental factors to between-individual variation in traits.
  
  
  RESULTS
  Additive genetic factors (ie, heritability) explained 47% of the variance in physical activity energy expenditure (95% CI: 23%, 53%) and time spent in moderate-to-vigorous intensity physical activity (95% CI: 29%, 54%), 35% of the variance in acceleration of the trunk (95% CI: 0%, 44%), and 31% of the variance in the time spent in sedentary behavior (95% CI: 9%, 51%). The remaining variance was predominantly explained by unique environmental factors and random error, whereas shared environmental factors played only a marginal role for all traits with a range of 0-15%.
  
  
  CONCLUSIONS
  The between-individual variation in daily physical activity and sedentary behavior is mainly a result of environmental influences. Nevertheless, genetic factors explain up to one-half of the variance, suggesting that innate biological processes may be driving some of our daily physical activity.
authors.affiliation: Medical Research Council Epidemiology Unit, University of Cambridge, Institute of Metabolic Science, Addenbrooke's Hospital, Cambridge, United Kingdom (MdH, SB, JHZ, KW, UE, NJW, and RJFL); the Department of Medical Sciences, Molecular Epidemiology and Science for Life Laboratory, Uppsala University, Uppsala, Sweden (MdH); the Department of Twin Research and Genetic Epidemiology Unit, St Thomas' Campus, King's College London, St Thomas' Hospital, London, United Kingdom (AN and TDS); the Department of Sports Medicine, Norwegian School of Sport Sciences, Oslo, Norway (UE); and The Charles Bronfman Institute for Personalized Medicine (RJFL), The Mindich Child Health and Development Institute (RJFL), and The Genetics of Obesity and Related Metabolic Traits Program (RJFL), The Icahn School of Medicine at Sinai School, New York, NY.
authors.forename: Marcel
authors.initials: M
authors.lastname: den Hoed
authors.forename: Søren
authors.initials: S
authors.lastname: Brage
authors.forename: Jing Hua
authors.initials: JH
authors.lastname: Zhao
authors.forename: Kate
authors.initials: K
authors.lastname: Westgate
authors.forename: Ayrun
authors.initials: A
authors.lastname: Nessa
authors.forename: Ulf
authors.initials: U
authors.lastname: Ekelund
authors.forename: Tim D
authors.initials: TD
authors.lastname: Spector
authors.forename: Nicholas J
authors.initials: NJ
authors.lastname: Wareham
authors.forename: Ruth J F
authors.initials: RJ
authors.lastname: Loos
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D004734:Energy Metabolism / Q000235:genetics*; D004777:Environment; D005260:Female; D059647:Gene-Environment Interaction; D006801:Humans; D008297:Male; D008875:Middle Aged; D009043:Motor Activity / Q000235:genetics*; D010641:Phenotype; D057185:Sedentary Behavior; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics; D055815:Young Adult
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