title: Heredity of chronic bronchitis: a registry-based twin study.
abstract: BACKGROUND
  Smoking is a major risk factor for lung diseases and lower respiratory symptoms, but since not all smokers develop chronic bronchitis and since chronic bronchitis is also diagnosed in never-smokers, it has been suggested that some individuals are more susceptible to develop chronic bronchitis due to genetics.
  
  
  OBJECTIVE
  To study the relative influence of genetic and environmental factors on the variation in the susceptibility to chronic bronchitis.
  
  
  METHODS
  In a population-based questionnaire study of 13,649 twins, 50-71 years of age, from the Danish Twin Registry, we calculated sex-specific concordance rates and heritability of chronic bronchitis. The response rate was 75%.
  
  
  RESULTS
  The prevalence of chronic bronchitis was 9.3% among men and 8.5% among women. The concordance rate for chronic bronchitis was higher in monozygotic twins than in dizygotic twins among women; 0.30 vs. 0.17, but not among men; 0.15 vs. 0.18. The heritability of chronic bronchitis adjusted for smoking and age was 55% (36-71%) in women, whereas the susceptibility to chronic bronchitis in men for 25% (8-41%) was ascribable to familial environment but not to genetic factors.
  
  
  CONCLUSIONS
  Chronic bronchitis shows a moderate familial aggregation, particularly in women. Increased susceptibility to respiratory disease among female smokers relative to male smokers may have a genetic origin.
authors: Respiratory and Allergy Research Unit, Bispebjerg Hospital, Copenhagen, Denmark. Electronic address: hmeteran@gmail.com.
authors: Howraman
authors: H
authors: Meteran
authors: Respiratory and Allergy Research Unit, Bispebjerg Hospital, Copenhagen, Denmark.
authors: Vibeke
authors: V
authors: Backer
authors: Odense Patient Data Exploratory Network, Institute of Regional Health Services Research, University of Southern Denmark, Odense, Denmark; The Danish Twin Registry, University of Southern Denmark, Odense, Denmark.
authors: Kirsten Ohm
authors: KO
authors: Kyvik
authors: The Danish Twin Registry, University of Southern Denmark, Odense, Denmark.
authors: Axel
authors: A
authors: Skytthe
authors: Respiratory and Allergy Research Unit, Bispebjerg Hospital, Copenhagen, Denmark.
authors: Simon Francis
authors: SF
authors: Thomsen
mesh_terms: D000368:Aged; D029481:Bronchitis, Chronic / Q000453:epidemiology / Q000235:genetics*; D003718:Denmark / Q000453:epidemiology; D004200:Diseases in Twins / Q000453:epidemiology / Q000235:genetics*; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D008875:Middle Aged; D015995:Prevalence; D012042:Registries; D014429:Twins, Dizygotic / Q000235:genetics; D014430:Twins, Monozygotic / Q000235:genetics
keywords: COPD; Chronic bronchitis; Heritability; Twin studies