Importance of Early COPD In Young Adults for Development of Clinical COPD: Findings from the Copenhagen General Population Study.

RATIONALE Individuals that will develop COPD could be identified at an early age before clinical manifestations appear. OBJECTIVE We investigated risk of Clinical COPD 10years 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 10years apart. Early COPD was defined as baseline FEV1/ FVC< LLN in individuals aged<50. Outcomes included Clinical COPD at final examination 10years later (chronic respiratory symptoms with FEV1/FVC<0.70 and FEV1<80% predicted) and acute exacerbation hospitalisations during follow-up. RESULTS Among 5,497 individuals aged<50 at baseline with FEV1/FVC≥0.70, 104(3%) developed Clinical COPD 10years later; 4% had Early COPD in smokers with ≥10pack-years, 3% in smokers with <10pack-years, and 2% in never-smokers. Among smokers with ≥10pack-years, 24% developed Clinical COPD in those with versus 4% in those without Early COPD. Corresponding numbers were 10% and 1% in smokers with <10pack-years, and 3% and <1% in never-smokers, respectively. Among individuals with Early COPD, odds ratios for Clinical COPD 10years later were 7.77(95%CI:4.10-14.7) in smokers with ≥10pack-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.