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Flowchart of the population included in the study. Between 2015 and 2021, a total of 1,264 patients were retrospectively reviewed; 528 were excluded from the analysis due to missing medical records, asthma, and interstitial lung disease. The number of patients with COPD (FEV1/FVC < 70%) was 736, which were eligible for this study. Of the 736 patients included, 236 cases had COPD with lung cancer, and 500 controls had COPD only.
