Relation between erythropoietin, hemoglobin and renal function in the oldest old. The Leiden 85-plus Study

Background In clinical practice, the occurrence of anemia in very old people is likely to be caused by an age-related low erythropoietin response. Erythropoietin response depends on renal function, which is often compromised in old age. The aim of our study was to unravel the relation between erythropoietin, hemoglobin and renal function in the oldest old. Methods Within the Leiden 85-plus Study, an observational population-based prospective follow-up study, erythropoietin, hemoglobin and creatinine levels were determined at the age of 86 (n=491). Anemia was defined as Hb <12 g/dL for women and Hb <13 g/dL for men. Creatinine clearance was estimated with the Cockcroft-Gault formula. Results The median (interquartile range) erythropoietin level was 10.2 mIU/mL (7.7-13.8 mIU/mL). In both anemic and non-anemic subjects the highest erythropoietin levels were found in subjects with the highest creatinine clearance. Subjects with creatinine clearance <30 mL/min had significantly lower hemoglobin levels (12 g/dL) than the subjects with creatinine clearance >60 mL/min (13 g/dL, p<0.001). Furthermore, participants with creatinine clearance <30 mL/min had significantly lower erythropoietin levels (9.1 mIU/mL) compared to subjects with creatinine clearance >60 mL/min (11.2 mIU/mL, ptrend=0.05). Conclusion Despite compromised renal function in the oldest old, erythropoietin production in response to anemia is relatively intact. Only when creatinine clearance was lower than 30 mL/min, relatively low erythropoietin levels were found in relation with hemoglobin levels, suggesting a causal relationship.