High rate of asthma among immigrants

Articles dealing with the epidemiological aspects of asthma were carefully reviewed in order to support or reject our clinical impression of increased rate of asthma among immigrants. Particular emphasis was put on data on very high or very low rates of asthma. The proposed theories to explain these differences were critically examined. The prevalence of asthma in China and in Africa is 1-2% and 0.5-5%, respectively. The prevalence of the disease in other indigenous populations ranges between 0.5% and 12%. On the other hand, asthma is much more frequently seen in Australia and in New Zealand (approximately 20-25%), where peoples' ancestors immigrated from distant areas. Statistical meta-analysis found a significant difference between the rates of asthma in the two groups of populations (P < 0.001). Immunoglobulin E levels of immigrants in Sweden are higher than those of native Swedes. Similarly, cord blood immunoglobulin E concentrations are more elevated in neonates whose mothers emigrated to Germany from Eastern countries than in those of native German mothers. There is an increased rate of IgE-mediated asthma among immigrant populations.