Cooking with biomass stoves and tuberculosis: a case control study.

OBJECTIVE To search for an association between tuberculosis and use of biomass stoves found recently in a cross sectional study. DESIGN In a case-control study based in a chest referral hospital, the cases were 288 patients with active smear-positive or culture-positive tuberculosis, and the controls were 545 patients with ear nose and throat ailments with no evidence of chest disease studied at the same time as the cases. Exposure to present or previous biomass smoke by history of cooking with traditional wood stoves was assessed by positive or negative response. RESULTS Exposure to biomass smoke was significantly higher in cases than in controls. Crude odds ratios for tuberculosis and biomass smoke exposure were 5.2 (95%CI 3.1-8.9) for current exposure, 3.4 (95%CI 2.4-5.0) for past or present exposure and 1.8 (95%CI 1.1-3.0) for past exposure. The association was observed only for patients living in Metropolitan Mexico City and urban or suburban areas in the center of Mexico providing most cases and controls. For rural areas, the power of the study was low and the origin of the patients heterogeneous. Odds ratio for Mexico City Metropolitan area and the center of Mexico was 2.4 (95%CI 1.04-5.6), adjusted for age, sex, level of education, crowding, smoking, socio-economic level, zone of residence and state of birth. In the same model smoking had an OR of 1.5 (95%CI 1.0-2.3) for tuberculosis. CONCLUSION Our results support a causal role of current domestic biomass smoke exposure in tuberculosis.