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.