title: Association between obesity and asthma in a twin cohort.
abstract: BACKGROUND
  Obesity is linked to asthma in a yet poorly understood manner. We examined the relationship between obesity and asthma in a population-based sample of twins.
  
  
  METHODS
  From the cohorts born between 1953 and 1982, who were enrolled in The Danish Twin Registry, a total of 29 183 twin individuals participated in a nationwide questionnaire study, where data on height, weight and asthma were collected. Latent factor models of genetic and environmental effects were fitted using maximum likelihood methods.
  
  
  RESULTS
  The age-adjusted risk of asthma was increased both in obese females, OR = 1.96 (1.45-2.64), P < or = 0.001 and in obese males, OR = 1.59 (1.08-2.33), P = 0.02. According to best-fitting models, the heritability for obesity was 81% in males and 92% in females, whereas the heritability for asthma was 78% and 68% in males and females respectively. The age-adjusted genetic liabilities to obesity and asthma were significantly correlated only in females, r = 0.28 (0.16-0.38).
  
  
  CONCLUSIONS
  Obese subjects have an increased risk for asthma, which in females seems partly because of common genes.
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, Copenhagen, Denmark.
authors.forename: S F
authors.initials: SF
authors.lastname: Thomsen
authors.forename: C S
authors.initials: CS
authors.lastname: Ulrik
authors.forename: K O
authors.initials: KO
authors.lastname: Kyvik
authors.forename: T I A
authors.initials: TI
authors.lastname: Sørensen
authors.forename: D
authors.initials: D
authors.lastname: Posthuma
authors.forename: L R
authors.initials: LR
authors.lastname: Skadhauge
authors.forename: I
authors.initials: I
authors.lastname: Steffensen
authors.forename: V
authors.initials: V
authors.lastname: Backer
mesh_terms: D000328:Adult; D017677:Age Distribution; D001249:Asthma / Q000453:epidemiology* / Q000235:genetics*; D015992:Body Mass Index; D015331:Cohort Studies; D015897:Comorbidity; D003718:Denmark / Q000453:epidemiology; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease / Q000235:genetics; D006801:Humans; D008297:Male; D009765:Obesity / Q000453:epidemiology* / Q000235:genetics*; D011159:Population Surveillance / Q000379:methods; D015995:Prevalence; D012307:Risk Factors; D012737:Sex Factors; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic