Exposure to cold and draught, alcohol consumption, and the NS-phenotype are associated with chronic bronchitis: an epidemiological investigation of 3387 men aged 53–75 years: the Copenhagen Male Study

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Abstract
OBJECTIVES This study was performed to estimate the strength of association between chronic bronchitis and lifetime exposure to occupational factors, current lifestyle, and the NS-phenotype in the MNS blood group among middle aged and elderly men. METHODS The study was carried out within the frameworks of the Copenhagen Male Study. Of 3387 men 3331 men with a mean age of 63 (range 53–75) years could be classified by prevalence of chronic bronchitis. As well as the completion of a large questionnaire on health, lifestyle, and working conditions, all participants had a thorough examination, including measurements of height and weight and blood pressure and a venous blood sample was taken for the measurement of serum cotinine and MNS typing; 16.5% of the men had the NS-phenotype. Chronic bronchitis was defined as cough and phlegm lasting 3 months or more for at least 2 years; 14.6% had chronic bronchitis. RESULTS Smoking and smoke inhalation were the factors most strongly associated with prevalence of chronic bronchitis. There were three major new findings: (a) long term (>5 years) occupational exposure to cold and draught was associated with a significantly increased prevalence of chronic bronchitis; compared with others, and adjusted for confounders, the odds ratio (OR) with 95% confidence interval (95% CI) was 1.4 (1.1 to 1.7), p=0.004; (b) a significant J shaped association existed between alcohol use and bronchitis, pc) a significant gene by environment association existed between smoking and the NS-phenotype in the MNS blood group; only among smokers was the NS-phenotype associated with a significantly decreased risk of chronic bronchitis, OR 0.67 (0.47-0.97), p=0.02. Other well known associations between dust, fumes, and even exposure to solvents and bronchitis were confirmed. CONCLUSION The results emphasise the multifactorial nature of chronic bronchitis, and show some hitherto unrecognised associations between cold and draught exposure, alcohol consumption, and the NS-phenotype and chronic bronchitis.