title: Risk of asthma in adult twins with type 2 diabetes and increased body mass index.
abstract: OBJECTIVE
  To examine the relationship between asthma, type 2 diabetes and increased body mass index (BMI) in adult twins.
  
  
  METHODS
  We performed record linkage between questionnaire-defined asthma and BMI, and hospital discharge diagnoses of type 2 diabetes in 34,782 Danish twins, 20-71 years of age.
  
  
  RESULTS
  The risk of asthma was increased in subjects with type 2 diabetes relative to nondiabetic subjects both in men (13.5%vs 7.5%), P = 0.001 and in women (16.6%vs 9.6%), P = 0.001. The result remained significant after adjustment for age, BMI, smoking, symptoms of chronic bronchitis, marital status and zygosity, men: OR = 1.70 (1.07-2.70), P = 0.026; women: OR = 1.88 (1.24-2.85), P = 0.003. In this analysis, BMI remained a highly significant predictor for asthma independently of diabetes status in women, P < 0.000 but not in men, P = 0.336. Significant positive genetic correlations were found between asthma and type 2 diabetes, 0.20 (0.01-0.40), P = 0.047; between asthma and BMI in women, 0.15 (0.07-0.22), P < 0.000; and between BMI and type 2 diabetes, 0.40 (0.29-0.43), P < 0.000.
  
  
  CONCLUSIONS
  Asthma, type 2 diabetes and increased BMI are strongly associated in adults, particularly in women. These results suggest a common aetiology for asthma and metabolic syndrome.
authors.affiliation: Department of Respiratory Medicine, Bispebjerg Hospital, Copenhagen, Denmark. sft@city.dk
authors.forename: S F
authors.initials: SF
authors.lastname: Thomsen
authors.forename: D L
authors.initials: DL
authors.lastname: Duffy
authors.forename: K O
authors.initials: KO
authors.lastname: Kyvik
authors.forename: A
authors.initials: A
authors.lastname: Skytthe
authors.forename: V
authors.initials: V
authors.lastname: Backer
mesh_terms: D000328:Adult; D000368:Aged; D001249:Asthma / Q000453:epidemiology* / Q000209:etiology*; D015992:Body Mass Index; D003924:Diabetes Mellitus, Type 2 / Q000150:complications*; D004200:Diseases in Twins / Q000453:epidemiology* / Q000276:immunology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012307:Risk Factors; D014427:Twins / Q000276:immunology; D055815:Young Adult