Airflow obstruction among young adults in Europe: a Chronic Airway Diseases Early Stratification (CADSET) collaboration with 48 612 individuals across eight population-based cohorts.

Background: The extent to which airflow obstruction, a key feature of COPD, can be already present in early adulthood is unclear. We investigated the prevalence of airflow obstruction in young adults across European populations. Methods: We identified 48 612 individuals aged 20-40 years across eight population-based European cohorts in the Chronic Airway Diseases Early Stratification (CADSET) collaboration and applied two commonly used definitions of airflow obstruction: pre-bronchodilator forced expiratory volume in 1 s (FEV1)/forced vital capacity (FVC) <0.70 and below the lower limit of normal (LLN). We explored how the prevalence of airflow obstruction according to both criteria was related to age, sex and smoking. Results: Airflow obstruction prevalence increased with increasing age from 2.3% in those aged 20-24.9 years to 6.3% in those aged 35-39.9 years according to FEV1/FVC <0.70, and from 7.3% to 8.3% according to FEV1/FVC <LLN. The corresponding increase in airflow obstruction prevalence was up to 8.8% in males versus 7.5% in females, and up to 9.0% in ever-smokers versus 6.9% in never-smokers. Difference in prevalence of airflow obstruction between FEV1/FVC <0.70 and <LLN was highest for females and ever-smokers. Active smoking ranged from 19% to 28% and ever-smoking from 37% to 51%. The prevalence of airflow obstruction increased with pack-years, plateauing at ∼5 pack-years. Conclusion: Up to 8% of young adults across Europe have airflow obstruction; its cause and its role in prior, concurrent and future airway disease merit further investigation.