Asthma attributable to atopy: does it depend on the allergen supply?

The use of the population attributable fraction (PAF) of asthma owing to atopy has not been widely used in epidemiological studies on childhood asthma, especially to compare regions of the same country. The present study includes 1039 children from Cartagena, Spain (Mediterranean coast) and 663 from Madrid (centre of Spanish plateau) using the ISAAC phase II methodology (questionnaire and prick test to the most common allergens). While there were no differences in asthma symptoms between school children (aged 10–11 yr) from Madrid and Cartagena, atopy to any allergen was significantly higher in those from Madrid (40.9% vs. 29.3%, respectively, p < 0.0001). However, children from Madrid were mainly positive to pollen allergy whereas those from Cartagena were positive for mite allergy. PAF of all the different asthma symptoms owing to atopy (any positive skin test) and PAF of current wheezing owing to a more severe atopy (three positive wheals) were higher in children from Cartagena than those from Madrid (45.5% vs. 28.6% and 14.2% vs. 6.2%, respectively). Per cent of previous year wheezing attributable to atopy to specific allergens varied among those cities and was higher for D. pteronissinus, D. farinae, cat, and olive tree in children from Cartagena, and – conversely – higher for mixed grasses, mixed trees and Alternaria in those from Madrid. All of these differences remained significant even after adjusting for risk factors. PAF for asthma owing to atopy could be very different within the same country, probably depending on the allergen supply which may depend on environmental factors such as the climate. [ABSTRACT FROM AUTHOR]