Incidence trends of airflow obstruction among European adults without asthma: a 20-year cohort study

Investigating COPD trends may help healthcare providers to forecast future disease burden. We estimated sex- and smoking-specific incidence trends of pre-bronchodilator airflow obstruction (AO) among adults without asthma from 11 European countries within a 20-year follow-up (ECRHS and SAPALDIA cohorts). We also quantified the extent of misclassification in the definition based on pre-bronchodilator spirometry (using post-bronchodilator measurements from a subsample of subjects) and we used this information to estimate the incidence of post-bronchodilator AO (AO(post-BD)), which is the primary characteristic of COPD. AO incidence was 4.4 (95% CI: 3.5–5.3) male and 3.8 (3.1–4.6) female cases/1,000/year. Among ever smokers (median pack-years: 20, males; 12, females), AO incidence significantly increased with ageing in men only [incidence rate ratio (IRR), 1-year increase: 1.05 (1.03–1.07)]. A strong exposure-response relationship with smoking was found both in males [IRR, 1-pack-year increase: 1.03 (1.02–1.04)] and females [1.03 (1.02–1.05)]. The positive predictive value of AO for AO(post-BD) was 59.1% (52.0–66.2%) in men and 42.6% (35.1–50.1%) in women. AO(post-BD) incidence was 2.6 (1.7–3.4) male and 1.6 (1.0–2.2) female cases/1,000/year. AO incidence was considerable in Europe and the sex-specific ageing-related increase among ever smokers was strongly related to cumulative tobacco exposure. AO(post-BD) incidence is expected to be half of AO incidence.