Rural to urban migration contributes to the high burden of asthma in the urban area.

Introduction It is unknown whether rural-urban migration contributes to worse the burden of asthma in the cities. Objectives The aim of this study was to evaluate whether subjects with asthma that migrated from rural areas to a large urban center in Brazil have more severe disease than asthmatic subjects that was born and always lived in the urban area. Methods This is a case-control study. We enrolled two groups of subjects with asthma currently living in a large urban center in Brazil: 486 subjects with moderate-severe asthma and 432 subjects with mild asthma. Results Rural-urban migrants had higher odds of moderate-severe asthma [adjusted OR 1.57, 95% CI (1.18-2.01)] and uncontrolled symptoms of asthma [adjusted OR 1.80, 95% CI (1.16-2.76)] than urban-born subjects. Conclusions Rural-urban migrants in Brazil have more severe asthma than urban-born subjects. Our results suggest that rural-urban migration is associated with the high burden of asthma in the urban area.