Risk factors of new-onset asthma in adults: A population-based international cohort study

Background: The occurrence of new-onset asthma during adulthood is common, but there is insufficient understanding of its determinants including the role of atopy. Objective: To assess the risk factors for the development of new-onset asthma in middle-aged adults and to compare them according to atopy. Methods: A longitudinal analysis of 9175 young adults who participated in two surveys of the European Community Respiratory Health Survey (ECRHS) conducted 9 years apart. Findings: We observed 179 cases of new-onset asthma among 4588 participants who were free of asthma and reported at the beginning of the follow-up that they had never had asthma (4.5 per 1000 person-years). In a logistic regression, the following risk factors were found to increase the risk of new-onset asthma: female gender (OR: 1.97; 95% confidence interval (CI): 1.38,2.81), bronchial hyperresponsiveness (3.25; 2.19,4.83), atopy (1.55;1.08,2.21), FEV₁ <100 % predicted (1.87;1.34,2.62), nasal allergy (1.98;1.39,2.84) and maternal asthma (1.91;1.13;3.21). Obesity, respiratory infections in early life and high-risk occupations increased the risk of new-onset asthma although we had limited power to confirm their role. Among the atopics, total IgE and sensitization to cat were independently related to the risk of new-onset asthma. The proportion of new-onset asthma attributable to atopy varied from 12% to 21%. Conclusion: Adults reporting that they had never had asthma were at a substantial risk of new-onset asthma as a result of multiple independent risk factors including lung function. Atopy explains a small proportion of new-onset adult asthma.