Relation between lung function and RBC distribution width in a population-based study

Study objectives: Pulmonary function is dependent not only on smoking, but also on nutritional status. Since an increased RBC distribution width (RDW) has been associated with nutritional deficiencies, we postulated that RDW has an inverse relation to pulmonary function. The purpose of this study was to test this hypothesis. Design and setting: A cross-sectional study was conducted of a random sample of the general population in western New York. Participants: A total of 1,616 subjects of both genders who were aged 35 to 79 years and were free of respiratory disease. Interventions: None. Measurements: Pulmonary function was assessed from FEV₁, FVC, height, body weight, total pack-years of smoking, smoking status, hemoglobin concentration, and hematologic indexes, eosinophil count, education, and blood levels of retinol, β-cryptoxanthin, and vitamin E. Results: We found a direct relation between RDW and the number of pack-years of smoking and smoking status, and an inverse relation between FEV₁ and FVC with RDW, even when potentially confounding variables such as smoking were taken into account. When the variabfiity of FEV₁ due to smoking was used for comparison, an additional 27% of that variability in FEV₁ was explained by variations in antioxidant vitamin levels, and another 24% by RDW. Conclusions: The results confirmed our hypothesis that there is an inverse relation between RDW and pulmonary function, and raise the possibility that RDW may be a biomarker for as-yet unidentified nutrients that affect pulmonary function.