Hypersensitivity pneumonitis in Mexico City.

Objective. To investigate the association between the urban area of origin of patients and the prevalence of hypersensitivity pneumonitis (HP), induce d by avian antigens. Material and methods. A case-control study was conduct ed in 1999 at the National Institute of Respiratory Diseases (NIRD). Cases were 109 consecutive HP patients and controls were 184 patients: 39 with id iopathic pulmonary fibrosis (IPF), 63 with pulmonary tuberculosis (PTB), an d 82 with asthma. Mexico City and surrounding counties (SC) were divided in to 5 geographical areas: 1) Downtown; 2) North-East (NE); 3) South-East (SE ); 4) North-West (NW) and 5) South-West (SW). Statistical analysis consiste d of calculation of disease prevalence by urban area; associations were ass essed with odds ratios and 95% confidence intervals. Multivariate analysis with multiple logistic regression was performed to adjust for age, gender a nd socioeconomic level. Results. Eighty HP cases were located in the NE sou thernmost and SE northernmost areas of Mexico City (48 and 32, respectively ) (OR=3.86; 95% CI 2.17-6.96). Thirty-six controls with asthma came from th e SW area, (where NIRD is located) (p<0.05), and four from SC. Controls wit h PTB and IPF were scattered throughout the study area. Conclusions. The NE southernmost and SE northernmost areas were associated with HP. The cause of HP may not be geographical; a garbage dump used to be located in this ar ea, suggesting that exposure to organic particles might contribute to the d evelopment of HP in susceptible individuals.