title: Motor Development and Physical Activity: A Longitudinal Discordant Twin-Pair Study.
abstract: BACKGROUND
  Previous longitudinal research suggests that motor proficiency in early life predicts physical activity in adulthood. Familial effects including genetic and environmental factors could explain the association, but no long-term follow-up studies have taken into account potential confounding by genetic and social family background. The present twin study investigated whether childhood motor skill development is associated with leisure-time physical activity levels in adulthood independent of family background.
  
  
  METHODS
  Altogether, 1550 twin pairs from the FinnTwin12 study and 1752 twin pairs from the FinnTwin16 study were included in the analysis. Childhood motor development was assessed by the parents' report of whether one of the co-twins had been ahead of the other in different indicators of motor skill development in childhood. Leisure-time physical activity (MET·h·d) was self-reported by the twins in young adulthood and adulthood. Statistical analyses included conditional and ordinary linear regression models within twin pairs.
  
  
  RESULTS
  Using all activity-discordant twin pairs, the within-pair difference in a sum score of motor development in childhood predicted the within-pair difference in the leisure-time physical activity level in young adulthood (P < 0.001). Within specific motor development indicators, learning to stand unaided earlier in infancy predicted higher leisure-time MET values in young adulthood statistically significantly in both samples (FinnTwin12, P = 0.02; and FinnTwin16, P = 0.001) and also in the pooled data set of the FinnTwin12 and FinnTwin16 studies (P < 0.001). Having been more agile than the co-twin as a child predicted higher leisure-time MET values up to adulthood (P = 0.03).
  
  
  CONCLUSIONS
  More advanced childhood motor development is associated with higher leisure-time MET values in young adulthood at least partly independent of family background in both men and women.
authors.affiliation: 1Department of Public Health, University of Helsinki, Helsinki, FINLAND, 2Department of Social Research, University of Helsinki, Helsinki, FINLAND; 3Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN; 4Department of Psychology, University of Jyvaskyla, Jyvaskyla, FINLAND, 5Department of Health Sciences, University of Jyvaskyla, Jyvaskyla, FINLAND, 6Institute for Molecular Medicine, University of Helsinki, Helsinki, FINLAND; and 7Department of Mental Health and Substance Abuse Services, National Institute for Health and Welfare, Helsinki, FINLAND.
authors.forename: Sari
authors.initials: S
authors.lastname: Aaltonen
authors.forename: Antti
authors.initials: A
authors.lastname: Latvala
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Rose
authors.forename: Lea
authors.initials: L
authors.lastname: Pulkkinen
authors.forename: Urho M
authors.initials: UM
authors.lastname: Kujala
authors.forename: Jaakko
authors.initials: J
authors.lastname: Kaprio
authors.forename: Karri
authors.initials: K
authors.lastname: Silventoinen
mesh_terms: D000328:Adult; D002648:Child; D002657:Child Development / Q000502:physiology*; D005260:Female; D006801:Humans; D007899:Leisure Activities; D008137:Longitudinal Studies; D008297:Male; D009043:Motor Activity / Q000502:physiology*; D009048:Motor Skills / Q000502:physiology*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic