Bronchial asthma in children: clinical and epidemiologic approach in different Portuguese speaking countries

Geographical differences in asthma prevalence are currently accepted, but evidence is sparse due to the lack of multicentre studies using the same protocol.

To compare the prevalence of asthma and atopy among schoolchildren from Portuguese speaking countries (ISAAC and Portuguese Study) and evaluate some environmental variables, such as house dust mite exposure.

Significant random samples of schoolchildren studied with standard validated methods--questionnaires, skin prick tests, methacholine bronchial challenge tests; dust bed sampling for analysis of mite antigens.

In the ISAAC study, in the 13-14 year-old age group, statistical significant differences were found, with higher wheezing prevalence in Brazil than in Portugal (two-fold). In the Portuguese Study, atopy prevalence ranged between 6.0 and 11.9% in Sal and S. Vicente (Cape Verde), up to 48.6 and 54.1% in Macau and Madeira. Active asthma had the higher values in Madeira (14.6%), and the lower in Macau (1.3%). Cape Verde had intermediate asthma prevalence (10.6 and 7.0%). The bronchial challenge test was positive in 25, 66 and 70% of asthmatic children from Sal, S. Vicente and Madeira respectively. Significant HDM antigen concentrations (Der p1) were found in Cape Verde and Madeira.

There are significant variations in asthma and atopy prevalence between these pediatric populations. The reasons remain under discussion, but genetics linked to race, seem to play a central role, modulated by environmental and lifestyle variables.