Elevated hemoglobin levels associated with severe sleep-disordered breathing in hemodialysis patients not receiving erythropoiesis-stimulating agents: a case series.

Elevated hemoglobin levels in hemodialysis patients not receiving erythropoiesis-stimulating agents (ESA) are uncommon and may suggest underlying hypoxic conditions. However, the clinical significance of sleep-disordered breathing (SDB) in this context remains underrecognized. We report three non-obese male patients undergoing maintenance hemodialysis without ESA or hypoxia-inducible factor prolyl hydroxylase inhibitor therapy who developed elevated hemoglobin levels. None of the patients exhibited typical symptoms of SDB. All were diagnosed with severe SDB based on sleep studies and were treated with continuous positive airway pressure (CPAP). CPAP adherence was assessed using device-recorded parameters, including average usage time, residual apnea–hypopnea index, and 95th percentile leak over a 3-month period. The degree of hemoglobin reduction appeared to correlate with CPAP usage time. Notably, elevated hemoglobin levels were observed despite relatively low ferritin levels in all cases. Hypoxia-inducible erythropoiesis and altered iron metabolism may explain these findings. In contrast to obstructive sleep apnea, where inflammation-associated hepcidin elevation may limit erythropoiesis, our cases—characterized by non-obesity, relative youth, and suspected central sleep apnea—may have involved less inflammation, allowing hypoxia-induced suppression of hepcidin and enhanced iron utilization. Elevated hemoglobin levels in hemodialysis patients not receiving ESA may be associated with unrecognized SDB, even in the absence of typical symptoms. The combination of elevated hemoglobin and relatively low ferritin may serve as a clinical clue to underlying SDB in this population.