Risk factors for incident asthma and COPD in a cohort of young adults.

INTRODUCTION: The aim of the study was to describe potential shared risk factors for incident asthma and COPD in a population-based, 9-year follow-up study.

METHODS: From a cohort of 1191 individuals, aged 20-44, who participated in baseline survey including spirometry, bronchial challenge, and skin prick test (SPT) 742 subjects (62%) were reexamined at follow-up in 2012-2014.

RESULTS: A total of 27 incident cases of asthma and 22 cases of COPD were identified at follow-up corresponding to an incidence rate of 5.8 (95% CI 3.9-8.4) and 3.5 (2.2-5.3) per 1000 person years, respectively. Among the identified COPD cases a total of 12 were Asthma-COPD Overlap Syndrome (ACOS). Atopy defined by positive SPT was a risk factor for asthma in males (OR 7.54; 95% CI 1.24-45.90), whereas risk factors in females were nasal allergy (3.81; 1.20-12.11), FEV1 <100% predicted (3.96; 1.07-14.62) and parental asthma (3.06; 1.00-9.40). Risk factors for COPD in males were bronchial hyperresponsiveness (23.13; 1.41-380.50) and FEV1 <100% predicted (all male cases had FEV1 <100% predicted) and in females current smoking (3.34; 1.16-9.59) and asthma at baseline (5.21; 1.48-18.34).

CONCLUSIONS: No shared risk factors for incident asthma and COPD were found. Despite low power when stratifying by sex risk factors for incident asthma and COPD emphasize considerable gender differences.