Worldwide impact of human development and inequality on the prevalence of asthma, rhinoconjunctivitis and eczema.

Background: Lower income countries have lower asthma prevalence. However, how differences in human development and inequality can explain changes in the prevalence of asthma and allergic diseases is not known. Methods: The Global Asthma Network Phase I study reported prevalence of asthma and allergic diseases in children (6-7 years), adolescents (13-14 years), and their parents/guardians in 16, 25 and 17 countries. Gini inequality index (GinI) and human development index (HDI), together with mean annual relative humidity and temperature, and latitude, were used as potential explanatory factors of prevalence differences using meta-regression models, fitted values and heatmaps of prevalence. Results: GinI and HDI explained some proportion of asthma prevalence variability, which was highest in children (up to ~70% for disease indicators such as current wheeze or symptoms of severe asthma) and lowest in adolescents (~22% for symptoms of severe asthma or asthma ever). Rhinoconjunctivitis prevalence variability was poorly explained by covariates (from ~53% for current rhinoconjunctivitis among children -an exception- to none). Eczema indicators were explained in a range from ~60% in children (current eczema symptoms and symptoms of severe eczema) to ~12% in adolescents (current eczema symptoms). Overall, heatmaps showed areas of higher prevalence in the intersection of high GinI and high HDI values. Conclusions: HDI and Gini explain part of the worldwide variability in the prevalence of asthma, rhinoconjunctivitis, and eczema. This explanatory power is highest for asthma and lowest for rhinoconjunctivitis. Individuals from lower-resourced communities in highly developed countries are at the greatest risk, particularly for asthma.