Cooking with biomass stoves and tuberculosis: a case control study

OBJECTIVE: To search for an association between tuberculosis and use of bio mass stoves found recently in a cross sectional study. DESIGN: In a case-control study based in a chest referral hospital, the cas es were 288 patients with active smear-positive or culture-positive tubercu losis, and the controls were 545 patients with car nose and throat ailments with no evidence of chest disease studied at the same time as the cases. E xposure to present or previous biomass smoke by history of cooking with tra ditional wood stoves was assessed by positive or negative response. RESULTS: Exposure to biomass smoke was significantly higher in casts than i n controls. Crude odds ratios for tuberculosis and biomass smoke exposure w ere 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 associat ion was observed only for patients living in Metropolitan Mexico City and u rban or suburban areas in the center of Mexico providing most cases and con trols. For rural areas, the power of the study was low and the origin of th e 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 a nd 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 s moke exposure in tuberculosis.