IMPORTANCE OF EARLY COPD IN YOUNG ADULTS FOR DEVELOPMENT OF CLINICAL COPD: FINDINGS FROM THE COPENHAGEN GENERAL POPULATION STUDY

Rationale:Individuals that will develop chronic obstructive pulmonary disease(COPD) could be identified at an early age before clinical manifestations appear. Objective:We investigated risk of Clinical COPD 10 years later in young adults from the general population with and without Early COPD with a focus on smoking exposure. Methods:We included 14,870 individuals aged 20-100 from the Copenhagen General Population Study with spirometry 10 years apart. Early COPD was defined as baseline forced expiratory volume in 1second(FEV1)/forced vital capacity(FVC)<lower limit of normal(LLN) in individuals aged<50. Outcomes included Clinical COPD at final examination 10 years later (chronic respiratory symptoms with FEV1/FVC<0.70 and FEV1<80% predicted) and acute exacerbation hospitalisations during follow-up. Measurements and Main Results:Among 5,497 individuals aged<50 at baseline with FEV1/FVC≥0.70, 104(3%) developed Clinical COPD 10 years later; 4% had Early COPD in smokers with ≥10 pack-years, 3% in smokers with <10 pack-years, and 2% in never-smokers. Among smokers with ≥10 pack-years, 24% developed Clinical COPD in those with versus 4% in those without Early COPD. Corresponding numbers were 10% and 1% in smokers with <10 pack-years, and 3% and <1% in never-smokers, respectively. Among individuals with Early COPD, odds ratios for Clinical COPD 10 years later were 7.77(95% CI:4.10-14.7) in smokers with ≥10 pack-years and 8.56(4.92-14.9) in all smokers, while hazard ratios for acute exacerbation hospitalisations were 4.16(95% CI:1.66-10.5) and 4.33(1.89-9.93), respectively. Results were validated in the Copenhagen City Heart Study. Conclusions:Depending on amount of smoking exposure, less than 24% of young adults in the general population with Early COPD develop Clinical COPD 10 years later. A smoking exposure threshold for Early COPD should be re-considered, as younger individuals are less represented in those with high smoking exposure.