Objective: To estimate the incidence of allergic rhinitis in schoolchildren in Castellón by comparing phases I and III of the International Study of Asthma and Allergies in Childhood (ISAAC), carried out in 1994 and 2002, respectively.
Material and methods: A cohort study was performed with 3607 schoolchildren aged 6-7 years old who participated in phase I of the ISAAC study. Of these, 1805 participated in phase III (8 years later) at the age of 14-15 years, with 1627 schoolchildren without allergic rhinitis in phase I. The cumulative incidence of allergic rhinitis was estimated. Two definitions of new cases of allergic rhinitis were used: the first was based on medical diagnosis or treatment of the disease, and the second also included symptoms of allergic rhinitis in the previous 12 months. Relative risks were calculated using Poisson regression.
Results: Participation was 50.0 %, and 151 new cases of allergic rhinitis according to the first definition (cumulative incidence of 9.3 % and 1.2 % per year) and 339 new cases according to the second definition (cumulative incidence of 20.8 % and 2.6 % per year) were found. No differences in incidence by gender were observed with the first definition (RR = 1.00 95 % CI 0.73-1.38) but with the second definition, the incidence was greater in girls (RR = 1.46 95 % CI 1.18-1.82).
Conclusions: The cumulative incidence of allergic rhinitis according to the first definition was in the range of incidence from cohort studies of adolescents.