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

The prevalence of iron deficiency in patients with chronic obstructive pulmonary disease (COPD) varies in previous studies. We aimed to assess its prevalence according to 3 well-known criteria for iron deficiency, its associations with clinical characteristics of COPD, and mortality.

In a cohort study consisting of 84 COPD patients, of which 21 had chronic respiratory failure, and 59 were non-COPD controls, ferritin, transferrin saturation (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.

The prevalence of iron deficiency in the study population was 10%-43% according to diagnostic criteria, and was consistently higher in individuals with COPD, peaking at 71% in participants with chronic respiratory failure. Ferritin < cutoff was significantly associated with forced expiratory volume in 1 second (FEV₁) (odds ratio [OR] 0.33 per liter increase), smoking (OR 3.2), and cardiovascular disease (OR 4.7). TSat < 20% was associated with body mass index (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 (hazard ratio [HR] 1.2-1.8).

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 levels of hemoglobin and increased BMI. Iron deficiency was not associated with increased mortality.