title: Variation in the prevalence of chronic bronchitis among smokers: a cross-sectional study.
abstract: OBJECTIVE
  Given the wide variations in prevalence of chronic obstructive pulmonary disease observed between populations with similar levels of exposure to tobacco smoke, we aimed to investigate the possibility of variations in prevalence of chronic bronchitis (CB) between two geographically distinct smoking populations in rural Karnataka, India.
  
  
  METHODS
  The Burden of Obstructive Lung Disease (BOLD) questionnaire was administered to all men aged >30 years in a cross-sectional survey. The χ(2) and Fisher's exact tests were used to compare CB prevalence in the two populations. Logistic regression was used to analyse the impact of multiple variables on the occurrence of CB.
  
  
  RESULTS
  Two samples of 2322 and 2182 subjects were included in the study. In non-smokers, CB prevalence did not differ between the populations. However, it was significantly different between smoking populations (44.79% vs. 2.13%, P < 0.0001). Logistic regression indicated that, in addition to smoking, region, age, occupational dust exposure and type of house were associated with higher likelihood of CB. An interaction between smoking and area of residence was found (P < 0.001) and appeared to explain the effect of region (without interaction).
  
  
  CONCLUSIONS
  A significant difference in CB prevalence was observed between male populations from two areas of Karnataka state, including when stratified by smoking status. No significant difference was observed between non-smokers.
authors.affiliation: <label>*</label>Department of Pulmonary Medicine, JSS Medical College, JSS University, Mysore, India.
authors.forename: P A
authors.initials: PA
authors.lastname: Mahesh
authors.affiliation: <label>*</label>Department of Pulmonary Medicine, JSS Medical College, JSS University, Mysore, India.
authors.forename: B S
authors.initials: BS
authors.lastname: Jayaraj
authors.affiliation: <label>*</label>Department of Pulmonary Medicine, JSS Medical College, JSS University, Mysore, India.
authors.forename: S K
authors.initials: SK
authors.lastname: Chaya
authors.affiliation: <label>*</label>Department of Pulmonary Medicine, JSS Medical College, JSS University, Mysore, India.
authors.forename: K S
authors.initials: KS
authors.lastname: Lokesh
authors.affiliation: <label><sup>†</sup></label>Barts Health NHS Trust, London, UK.
authors.forename: A J
authors.initials: AJ
authors.lastname: McKay
authors.affiliation: <label>*</label>Department of Pulmonary Medicine, JSS Medical College, JSS University, Mysore, India.
authors.forename: A K
authors.initials: AK
authors.lastname: Prabhakar
authors.affiliation: <label><sup>‡</sup></label>Department of Primary Care & Public Health, Faculty of Medicine, Imperial College London, UK.
authors.forename: U J
authors.initials: UJ
authors.lastname: Pape
mesh_terms: D000328:Adult; D000367:Age Factors; D000368:Aged; D029481:Bronchitis, Chronic / Q000453:epidemiology*; D003430:Cross-Sectional Studies; D004391:Dust; D006801:Humans; D007194:India / Q000453:epidemiology; D016015:Logistic Models; D008297:Male; D008875:Middle Aged; D016273:Occupational Exposure / Q000009:adverse effects; D015995:Prevalence; D012111:Residence Characteristics / Q000706:statistics & numerical data; D012307:Risk Factors; D012424:Rural Population / Q000706:statistics & numerical data*; D012907:Smoking / Q000453:epidemiology*; D011795:Surveys and Questionnaires; D014028:Tobacco Smoke Pollution / Q000706:statistics & numerical data*
chemical_list: D004391:Dust; D014028:Tobacco Smoke Pollution