Prevalence of asthma, allergic rhinoconjunctivitis and allergic sensitization in Mongolia.

BACKGROUND

Studies in countries, such as Mongolia, which are in transition from farming to industrial society permit evaluation of the impact of environmental change on atopic diseases.

METHODS

In the screening study, questionnaire data were obtained from 9453 subjects aged 10-60 years. In the clinical study, a subsample of 869 subjects (participation rate 50.0%) was examined. A questionnaire-based interview, clinical examination, skin prick tests, spirometry and bronchodilation test or methacholine challenge test were used to define the clinical diagnoses. The prevalences of atopic diseases were evaluated at the population level using two-phase data and sampling weights.

RESULTS

The prevalences of asthma, allergic rhinoconjunctivitis and allergic sensitization with 95% confidence intervals were 1.1% (0.3-2.0%), 9.3% (4.0-14.6%) and 13.6% (7.4-19.9%) in Mongolian villages, 2.4% (1.4-3.5%), 12.9% (8.2-17.7%) and 25.3% (17.1-33.6%) in rural towns and 2.1% (1.3-3.0%), 18.4% (13.3-23.4%) and 31.0% (24.5-37.5%) in Ulaanbaatar city, respectively. The prevalence of allergic rhinoconjunctivitis (P = 0.02) and allergic sensitization (P = 0.003) increased significantly with increasing urbanization.

CONCLUSIONS

The prevalences of atopic diseases were low in rural Mongolia and increased with increasing urbanization suggesting that rural living environment protects against atopy.