RESUMEN
Background: In developed countries, the prevalence of asthma in children has significantly increased in the last decades. However, there is no information about the trends of asthma in Latin America. Aim: To determine changes in asthma prevalence between 1994 and 2002 in Chilean schoolchildren. Material and methods: The prevalence of asthma symptoms in schoolchildren aged 7 (n =18.697) and 13 years (n =18.939), from South Santiago, Valdivia and Punta Arenas, obtained during phases I and III of the ISAAC, carried out in 1994 and 2002, was compared. Results: From 1994 to 2002, the mean national prevalence of "wheezing in the last 12 months" in the group aged 6-7years, changed from 18.2 percent to 17.9 percent (p =NS); "asthma ever" from 12.5 percent to 10.7 percent (p =NS), and "severe episode" from 3.2 percent to 2.8 percent (p =NS). There was a significant increase of the prevalence of "wheezing in the last 12 months", in children aged 13-14years, from 9.8 percent to 15.5 percent (p =0.01); in "asthma ever" from 10.2 percent to 14.9 percent (p =0.01), and for "severe episode" from 2.8 percent to 3.8 percent (p =0.01). Conclusions: There was a significant increase in the prevalence of respiratory symptoms related to asthma in children aged 13-14 years that was consistent in all the 3 participating centres of the ISAAC. However, the prevalence of asthma symptoms in children aged 6-7 years remained without significant changes between 1994 and 2002.