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Interaction between Smoking and Genetic Factors in the Development of Chronic Bronchitis

¹ Department of Public Health Sciences, and ² Centre for Allergy Research, Karolinska Institutet, Stockholm, Sweden; ³ Department of Occupational and Environmental Health, Stockholm County Council, Stockholm, Sweden; ⁴ Department of Medical Epidemiology and Biostatistics, Karolinska Institutet, Stockholm, Sweden; ⁵ AstraZeneca R&D, Lund, Sweden; and ⁶ Clinical Science, AstraZeneca R&D, Charnwood, United Kingdom

Correspondence and requests for reprints should be addressed to Jenny Hallberg, M.Sc., Department of Occupational and Environmental Health, Norrbacka, Karolinska Hospital, SE-171 76 Stockholm, Sweden. E-mail: jenny.hallberg{at}sll.se

Rationale: 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.

Objectives: 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.

Measurements and Main 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.

Key Words: chronic bronchitis • smoking • chronic obstructive pulmonary disease • twin study • genes

AT A GLANCE COMMENTARY Scientific Knowledge on the Subject The relative importance of the role that genetic factors play in the development of chronic bronchitis has not been quantified. It is unclear if the genetic factors influencing chronic bronchitis are the same as those contributing to smoking behavior. What This Study Adds to the Field Genetic factors independent of those related to smoking habits play a role in the development of chronic bronchitis.