Cigarette smoking as a risk factor for tuberculosis in young adults: a case-control study.

Setting: The association between smoking and pulmonary tuberculosis has not often been studied.

Objective: To assess the influence of cigarette smoking on the development of active pulmonary tuberculosis in young people who were close contacts of new cases of smear-positive pulmonary tuberculosis.

Design: A case-control study in which 46 'cases' (patients with active pulmonary tuberculosis: isolation of Mycobacterium tuberculosis or clinical and/or radiographic evidence of current pulmonary tuberculosis, with a positive tuberculin skin test) and 46 'controls' (persons with positive tuberculin reaction, negative bacteriological test and without clinical and/or radiological evidence of pulmonary tuberculosis) were included. Smoking habits were investigated by questionnaire. Univariate and multivariate analysis was performed, and odds ratio (OR) was adjusted for age, gender and socio-economic status.

Results: Statistically significant differences were found in active smokers (occasional and daily smokers) (OR: 3.65; 95% CI, 1.46 and 9.21; P < 0.01), daily smokers (OR: 3.53; 95% CI, 1.34 and 9.26; P < 0.05), and individuals who were both passive and active smokers (OR: 5.10; 95% CI, 1.97 and 13.22; P < 0.01) and passive and daily smokers (OR: 5.59; 95% CI, 2.07 and 15.10; P < 0.001). There was a dose-response relationship between the number of cigarettes smoked daily and the risk of active pulmonary tuberculosis.

Conclusions: The data studied show that cigarette smoking is a risk factor for pulmonary tuberculosis in young people, with a dose-response relationship with the number of cigarettes consumed daily.