Chronic obstructive pulmonary disease (COPD) is characterized by varying trajectories of decline. Information regarding the prognostic value of preventing short-term clinically important deterioration (CID) in lung function, health status, or first moderate/severe exacerbation as a composite endpoint of worsening is needed. We evaluated post hoc the link between early CID and long-term adverse outcomes. CID was defined as ≥100 mL decrease in forced expiratory volume in 1 s (FEV ), ≥4-unit increase in St George's Respiratory Questionnaire (SGRQ) score from baseline, and/or a moderate/severe exacerbation during enrollment in two 3-year studies. Presence of CID was assessed at 6 months for the principal analysis (TORCH) and 12 months for the confirmatory analysis (ECLIPSE). Association between presence (+) or absence (-) of CID and long-term deterioration in FEV , SGRQ, future risk of exacerbations, and all-cause mortality was assessed. In total, 2870 (54%; TORCH) and 1442 (73%; ECLIPSE) patients were CID+. At 36 months, in TORCH, CID+ patients (vs CID-) had sustained clinically significant worsening of FEV (- 117 mL; 95% confidence interval CI: - 134, - 100 mL; P < 0.001) and SGRQ score (+ 6.42 units; 95% CI: 5.40, 7.45; P < 0.001), and had higher risk of exacerbations (hazard ratio HR: 1.61 95% CI: 1.50, 1.72; P < 0.001) and all-cause mortality (HR: 1.41 95% CI: 1.15, 1.72; P < 0.001). Similar risks post-CID were observed in ECLIPSE. A CID within 6-12 months of follow-up was consistently associated with increased long-term risk of exacerbations and all-cause mortality, and predicted sustained meaningful loss in FEV and health status amongst survivors. NCT00268216 ; NCT00292552 .