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[Time trends in prevalence of symptoms of allergic rhinitis in 13-14 year-old schoolchildren in 8 areas of Spain between 1993-1994 and 2001-2002 according to the International Study of Asthma and Allergies in Childhood (ISAAC)].

BACKGROUND AND OBJECTIVE
Our goal was to estimate the time trends in the prevalence of symptoms of allergic rhinitis (AR) and its geographic variations.


POPULATION AND METHOD
During 2001-2002, the phase 3 of ISAAC study was carried out, and a comparison with the phase 1 (1993-1994) was done. This cross sectional study included 30,046 schoolchildren 13-14 years-old from 9 centers (Asturias, Barcelona, Bilbao, Cartagena, Castellon, Madrid, Pamplona, Valencia, and Valladolid). A questionnaire about rhinitis symptoms self-administered to schoolchildren was used at schools and institutes with a participation rate of 100% to 75.8%.


RESULTS
A divergent time trend of AR prevalence symptoms was observed with a decrease in Barcelona and Bilbao, a stabilization in Cartagena, Pamplona, and Valencia, and an increase in Castellon; Madrid and Valladolid; however, there was an overall increase in nasal allergy. The prevalence of rhinoconjunctivitis in the past year (Prevalence Ratio [PR] = 1,13; 95% Confidence Interval [CI], 1.07-1.19) and nasal allergy ever (PR = 1.22; 95% CI, 1.15-1.30) increased after adjusting for gender, center and season change. The prevalence of rhinoconjunctivitis and nasal allergy varied according to centres, Madrid, Asturias, Cartagena and Bilbao exhibiting the higher prevalence. Taken as a whole, these data indicate a middle prevalence of AR when compared with other countries following an ISAAC methodology.


CONCLUSIONS
Two patterns of time trend of prevalence of symptoms of AR were observed. The investigation of risk factors at local level could be important in order to undertake preventive measures.