Nutritional anemia is associated with increased risk of severe COPD exacerbations: a prospective cohort study

Background Anemia prevalence in chronic obstructive pulmonary disease (COPD) varies widely across studies, and data on anemia subtypes and their association with mortality or COPD exacerbation readmission is limited. Objective We aimed to investigate anemia subtypes and their association with mortality and readmission for acute exacerbation of COPD (AECOPD) in patients hospitalized for AECOPD. Methods In this prospective observational cohort study, COPD patients ≥45 years hospitalized for severe exacerbations in a Belgian nationwide database were included. Cox regression models investigated associations between anemia (or its subtypes) and (post-discharge) mortality and AECOPD readmission, adjusted for age, sex, socio-economic status, smoking, weight and age-adjusted Charlson Comorbidity Index. Inverse probability of treatment weighting examined the association between anemia treatment and mortality across anemia subtypes. Results Among 32,152 COPD patients discharged from hospital, 5,956 (18.5%) had anemia. Nutritional anemia was most frequent (49.3%), followed by anemia of chronic disease (ACD) (31.3%). Anemia was associated with a 30% higher post-discharge mortality risk (adjusted hazard ratio (aHR) 1.30, 95%CI 1.23, 1.37), and 8% higher readmission risk (aHR 1.08, 95%CI 1.03, 1.14). Patients with hematologic anemia had the highest post-discharge mortality risk (aHR 1.75, 95%CI 1.54, 1.99), followed by nutritional anemia (aHR 1.29, 95%CI 1.20, 1.39). Only nutritional anemia was associated with increased readmission risk (aHR 1.18, 95%CI 1.10, 1.25). Treatment effects differed by anemia subtype, with iron, vitamin B12, and erythroid stimulating agent (ESA) associated with lower post-discharge mortality in nutritional anemia; folic acid and iron in hematologic anemia; and ESA and iron in ACD. Conclusions Nutritional anemia was the predominant subtype in hospitalized AECOPD patients and its increased readmission risk calls closer attention to iron deficiency in COPD patients. All subtypes of anemia were associated with higher post-discharge mortality risk, but targeted treatment may reduce mortality risk and represents a potential strategy to improve outcomes.