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.