Background:

Anemia is a well-known comorbidity of COPD. Previous studies regarding hemoglobin and polycythemia have been investigated to be associated with increased mortality. In this study , we aimed to retrospectively investigate the risk of mortality to serum hemoglobin(Hb) concentration level in COPD patients.

Methods:

A retrospective cohort study was designed using the Korean National Health Insurance Service (NHIS) -National Sample Cohort database. Patients diagnosed with COPD at least twice annually were enrolled between 2003 and 2004. And the patients were followed up until 2019 or death. We identified COPD patients with available Hb level and smoking history. Pateints were divided into three groups according to the Hb level(Anemia: male< 13g/dL, female<12g/dL, Normal, Secondary polycythemia: male > 16.5g/dL, female: 16>g/dL). We calculated the incidence rate, hazard ratio(HR), and 95% confidence interval (CI) using a stratified Cox proportional hazard model.

Results:Anemia group was older than other groups (68.18±10.26 in anemia vs 64.05±10.28 in normal vs 61.68±10.62 in polycythemia). Current smoker and former smoker proportion in  polycythemia group was higher than other groups. The overall mortality rate was 60.8% in anemia group and 43.0% in normal group and 45.3% in polycythemia group. The HR of anemia for mortality was 1.238 (95%CI : 1.175-1.305). And the hazard ratio of secondary polycythemia was 1.141 (95%CI : 1.016-1.283). 

Conclusion:

This large cohort study in South Korea, mortality was the highest in anemia group. And secondary polycythemia COPD group were at a statistically higher risk for mortality than normal Hb concentration COPD group.