title: Concordance rates of insulin dependent diabetes mellitus: a population based study of young Danish twins.
abstract: OBJECTIVE
  To study the genetic contribution to the aetiology of insulin dependent diabetes mellitus.
  
  
  METHODS
  Historical cohort study of twins, with information on diabetes being gathered by questionnaire, verification of the diagnosis by the subject's diabetologist or general practitioner, and clinical examination in available twins.
  
  
  METHODS
  Danish twin register and diabetic clinics and general practices throughout Denmark.
  
  
  METHODS
  20,888 twin pairs born during 1953-82, included in a population based nationwide register.
  
  
  METHODS
  Crude and cumulative concordance rates and heritability in monozygotic and dizygotic twins.
  
  
  RESULTS
  The crude probandwise concordance rate was 0.53 (95% confidence interval 0.33 to 0.73) for monozygotic twin pairs and 0.11 (0.05 to 0.21) for dizygotic twin pairs. When adjusted for age at onset of diabetes and age at last observation among unaffected twin partners the cumulative proband-wise risk from birth to age 35 was estimated as 0.70 (0.45 to 0.95) for monozygotic twins and 0.13 (0.05 to 0.20) for dizygotic twins. The correlations of liability for monozygotic and dizygotic twin pairs were estimated as 0.96 (SE 0.09) and 0.58 (0.07), with a heritability estimate of 0.72 (0.21).
  
  
  CONCLUSIONS
  The risk of insulin dependent diabetes in monozygotic twins is higher than previously thought and for dizygotic twins is higher than in ordinary first degree relatives. Based on the findings of this study the genetic component to the disease seems more important than hitherto believed.
authors.affiliation: Genetic Epidemiology Research Unit, Institute of Community Health, Odense University, Denmark.
authors.forename: K O
authors.initials: KO
authors.lastname: Kyvik
authors.forename: A
authors.initials: A
authors.lastname: Green
authors.forename: H
authors.initials: H
authors.lastname: Beck-Nielsen
mesh_terms: D015331:Cohort Studies; D016001:Confidence Intervals; D003718:Denmark / Q000453:epidemiology; D003922:Diabetes Mellitus, Type 1 / Q000453:epidemiology / Q000209:etiology / Q000235:genetics*; D006801:Humans; D012307:Risk Factors; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic