COPD: Iron Deficiency and Clinical Characteristics in Patients With and Without Chronic Respiratory Failure.

Background The prevalence of iron deficiency in patients with COPD varies in previous studies. We aimed to assess its prevalence according to three well-known criteria for iron deficiency, its associations with clinical characteristics of COPD and mortality. Methods In a cohort study consisting of 84 COPD patients, of which 21 had chronic respiratory failure, and 59 non-COPD controls, ferritin, TSat and mortality across 6.5 years were assessed. Associations between clinical characteristics and iron deficiency were examined by logistic regression, while associations with mortality were assessed in mixed effects Cox regression analyses. Results The prevalence of iron deficiency in the study population was 10-43% according to diagnostic criteria, and was consistently higher in COPD, peaking at 71% in participants with chronic respiratory failure. Ferritin < cutoff was significantly associated with FEV1 (OR 0.33 per liter increase), smoking (OR 3.2) and cardiovascular disease (OR 4.7). TSat < 20% was associated with BMI (OR 1.1 per kg/m2 increase) and hemoglobin (OR 0.65 per g/dL increase). The combined criterion of low ferritin and TSat was only associated with FEV1 (OR 0.39 per liter increase). Mortality was not significantly associated with iron deficiency (HR 1.2-1.8) in adjusted analyses. Conclusion The prevalence of iron deficiency in the study population increased with increasing severity of COPD. Iron deficiency, defined by ferritin < cutoff, was associated with bronchial obstruction, current smoking and cardiovascular disease, while TSat < 20% was associated with reduced level of hemoglobin and increased BMI. Iron deficiency was not associated with increased mortality.