Tobacco smoking and pulmonary tuberculosis.

BACKGROUND The prevalence of tuberculosis in adult men in India is 2-4 times higher than in women. Tobacco smoking is prevalent almost exclusively among men, so it is possible that tobacco smoking may be a risk factor for developing pulmonary tuberculosis. A nested case control study was carried out to study the association between tobacco smoking and pulmonary tuberculosis. METHODS A tuberculosis disease survey was carried out in two Panchayat unions in the Tiruvallur district of Tamil Nadu in India. Eighty five men aged 20-50 years with bacteriological tuberculosis (smear and/or culture positive) were selected as cases and 459 age matched men without tuberculosis were selected randomly as controls. Information on smoking status, type of tobacco smoked, quantity of tobacco smoked, and duration of tobacco smoking was collected from cases and controls using a questionnaire. RESULTS The estimated crude odds ratio (OR) of the association between tobacco smoking and bacillary tuberculosis was 2.48 (95% confidence interval (CI) 1.42 to 4.37), p<0.001. The age adjusted OR (Mantel-Hanszel estimate) was 2.24.(95% CI 1.27 to 3.94), p<0.05. The ORs for mild (1-10 cigarettes/day), moderate (11-20/day), and heavy (>20/day) smokers were 1.75, 3.17, and 3.68, respectively (p<0.0001 test for linear trend). The ORs for smokers with <10 years, 11-20 years, and >20 years of smoking were 1.72, 2.45, and 3.23, respectively (p<0.0001 test for linear trend). CONCLUSION There is a positive association between tobacco smoking and pulmonary (bacillary) tuberculosis (OR 2.5). The association also shows a strong dose-response relationship.