Prevalence of asthma and allergic symptoms in Suzhou, China: Trends by domestic migrant status.

Rapid urbanization in developing countries, with significant rural-to-urban and between-urban areas migration, presents a natural epidemiological model to better understand population-level trends in asthma and allergy prevalance without confounding by genetic factors. This cross-sectional study, conducted November 2014 to January 2015 in Suzhou, China, investigated differences in asthma and allergic symptoms between domestic migrant residents and long-term residents and their children. Using multivariate logistic regression, the odds ratios for children in migrant families compared to those in long-term resident families in Suzhou for doctor-diagnosed asthma, pneumonia, rhinitis, and eczema were 0.56 (95% CI: 0.42.0.73), 0.60 (95% CI: 0.49, 0.72), 0.63 (95% CI:0.52, 0.77), and 0.73 (95% CI: 0.60, 0.89), respectively. While there was a lower prevalence of asthma and allergic symptoms for domestic migrants (children and parents) compared to the local population in Suzhou, migrant children had a higher asthma rate than their parents. This follows the trend of increasing asthma rates for children in the urban local population, suggesting an environmental component. Parental migration plays a role in both parental and children's health but further investigations are needed to determine how these results may be shaped by early life exposures, lifestyle differences, and other environmental factors.