Incidence of asthma in young adults from Castellon, Spain: A prospective cohort study

The objective was to estimate the incidence of asthma in young adults from 13–15 years old to 23–25 years old, and associated factors. In 2012, a population-based prospective cohort study was carried out in Castellon from the cohort who had participated in the International Study of Asthma and Allergy in Childhood in 1994 and 2002. A telephone survey was undertaken using the same questionnaires. A new case of asthma was defined as a participant free of the disease in 2002 who suffered asthma, was diagnosed with asthma, or took medications against asthma based on self-report from 2002 to 2012. The mean age of participants was 24.9±0.6 with a follow-up of 79.1%. Asthma cumulative incidence was 3.4%: 44 new cases occurred among 1280 participants. The incidence was higher in females than males with relative risk (RR)=2.02 (95% confidence interval [CI] 1.1–3.8). A significant decrease of asthma incidence density was observed (8.2 cases to 3.5 cases per 1000 person/year). Factors associated with the incidence of asthma were allergic rhinitis (RR=4.05; 95% CI 1.7–9.6), bronchitis (RR=2.13; 95% CI 1.0–4.5), mother's age at time of birth (RR=0.87; 95% CI 0.8–0.9) and a pet other than a dog or cat (RR=0.42; 95% CI 0.2–0.9). For gender, some variations in the risk factors were observed. A significant decrease in the incidence of asthma was observed. Several risk and protective factors were found.