title: The genetic epidemiology of joint hypermobility: a population study of female twins.
abstract: OBJECTIVE
  To estimate the genetic influence on joint hypermobility in an unselected population using a classic twin study design.
  
  
  METHODS
  A self-report questionnaire on joint hypermobility as well as data on age, height, weight, estrogen replacement therapy, and menopause status were obtained from 483 monozygotic (MZ) and 472 dizygotic (DZ) unselected female twin pairs ages 21-81 years who were registered with the St Thomas' Adult Twin Registry in the UK.
  
  
  RESULTS
  The overall prevalence of hypermobility was 19.5% in MZ twins and 22.1% in DZ twins. The prevalence of hypermobile joints declined with age, falling from 34% in subjects ages 20-30 years to 18.4% in those ages 60 years or older. Significantly greater concordance for joint hypermobility was observed in the MZ twins when compared with the DZ twins (60% versus 36%), consistent with a genetic influence. In variance components analysis, the age- and body mass index-adjusted heritability of joint hypermobility was estimated to be 70% (95% confidence interval 57-89%).
  
  
  CONCLUSIONS
  Genetic factors have a substantial contribution to joint hypermobility in the adult female population.
authors.affiliation: The Twin Research and Genetic Epidemiology Unit, St Thomas' Hospital, London, UK. alan.hakim@whippsx.nhs.uk
authors.forename: Alan J
authors.initials: AJ
authors.lastname: Hakim
authors.forename: Lynn F
authors.initials: LF
authors.lastname: Cherkas
authors.forename: Rodney
authors.initials: R
authors.lastname: Grahame
authors.forename: Tim D
authors.initials: TD
authors.lastname: Spector
authors.forename: Alexander J
authors.initials: AJ
authors.lastname: MacGregor
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D005260:Female; D006801:Humans; D007593:Joint Instability / Q000453:epidemiology* / Q000235:genetics*; D008875:Middle Aged; D015995:Prevalence; D011795:Surveys and Questionnaires; D014430:Twins, Monozygotic; D006113:United Kingdom / Q000453:epidemiology