Interaction between smoking and genetic factors in the development of chronic bronchitis.
BACKGROUND
Smoking is a primary risk factor for chronic bronchitis, emphysema, and chronic obstructive pulmonary disease, but since not all smokers develop disease, it has been suggested that some individuals may be more susceptible to exogenous factors, such as smoking, and that this susceptibility could be genetically determined.


OBJECTIVE
The aim of the present study was to assess, in a population-based sample of twins, the following: (1) to what extent genetic factors contribute to the development of chronic bronchitis, including emphysema, taking sex into consideration, and (2) whether the genetic influences on chronic bronchitis, including emphysema, are separate from those for smoking behavior.


METHODS
Disease cases and smoking habits were identified in 44,919 twins older than 40 years from the Swedish Twin Registry. Disease was defined as self-reported chronic bronchitis or emphysema, or recurrent cough with phlegm. Individuals who had smoked 10 pack-years or more were defined as smokers. Univariate and bivariate structural equation models were used to estimate the heritability specific for chronic bronchitis and that in common with smoking.


RESULTS
The heritability estimate for chronic bronchitis was a moderate 40% and only 14% of the genetic influences were shared with smoking.


CONCLUSIONS
Genetic factors independent of those related to smoking habits play a role in the development of chronic bronchitis.
Hallberg
Jenny
J
Department of Occupational and Environmental Health, Norrbacka, Karolinska Hospital, SE-171 76 Stockholm, Sweden. jenny.hallberg@sll.se
Dominicus
Annica
A
Eriksson
Ulrika K
UK
Gerhardsson de Verdier
Maria
M
Pedersen
Nancy L
NL
Dahlbäck
Magnus
M
Nihlén
Ulf
U
Higenbottam
Tim
T
Svartengren
Magnus
M
D000328:Adult; D029481:Bronchitis, Chronic / Q000453:epidemiology* / Q000235:genetics*; D004200:Diseases in Twins / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D020022:Genetic Predisposition to Disease; D006801:Humans; D008297:Male; D015995:Prevalence; D012307:Risk Factors; D012737:Sex Factors; D012907:Smoking / Q000453:epidemiology*; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic