Anemia as a Significant Predictor of Adverse Outcomes in Hospitalized Patients With Acute Exacerbations of Chronic Obstructive Pulmonary Disease: Analysis of National (Nationwide) Inpatient Sample Database

Background: Acute exacerbation of chronic obstructive pulmonary disease (AECOPD) has significant health implications. Anemia is usually an unseen comorbidity, which could significantly affect outcomes in AECOPD patients, and there is limited data to support this. We conducted this study to assess the effect of anemia on this patient population. Methods: We performed a retrospective cohort study using the National (Nationwide) Inpatient Sample (NIS) data from 2008 to 2014. Patients with AECOPD and anemia with age >40 years were identified using appropriate International Classification of Diseases, Ninth Revision (ICD-9) codes, excluding transfer out to other hospitals. We calculated the Charlson Comorbidity Index as a measure of associated comorbidities. We analyzed bivariate group comparisons in patients with and without anemia. Odds ratios were calculated using multivariate logistic and linear regression analysis using SAS version 9.4 (2013; SAS Institute Inc. Cary, North Carolina, United States). Results: Among 3,331,305 patients hospitalized with AECOPD, 567,982 (17.0%) had anemia as a comorbidity. The majority of patients were elderly, women, and white. After adjusting for potential confounders in regression, mortality (adjusted OR (aOR) 1.25, 95%CI: 1.18-1.32), length of hospital stay (β 0.79, 95%Cl 0.76-0.82), and hospitalization cost (β 6873, 95%Cl 6437-7308) were significantly higher in patients with anemia. In addition, patients with anemia required significantly higher blood transfusion (aOR 16.9, 95%CI 16.1-17.8), invasive ventilator support (aOR 1.72, 95%CI 1.64-1.79), and non-invasive ventilator support (aOR 1.21, 95%CI 1.17-1.26). Conclusion: In this first retrospective largest cohort study on this topic, we find anemia is a significant comorbidity associated with adverse outcomes and healthcare burden in hospitalized AECOPD patients. We should focus on close monitoring and management of anemia to improve the outcomes in this population.