Aims:

Obstructive sleep apnea (OSA) may cause secondary erythrocytosis due to sustained hypoxemia. However, controversial findings have also been reported. The present study investigated the relationship between hematological parameters and OSA severity.

Methods:

This retrospective study included individuals who underwent a polysomnography test. Patients were divided into 4 groups based on their apnea-hypopnea index: normal, mild, moderate, and severe OSA. Hemoglobin (HGB), red blood cell (RBC), hematocrit (HCT), red cell distribution width (RDW), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), white blood cell (WBC), #neutrophil, #lymphocyte, erythrocyte sedimentation rate (ESR) and serum lactate dehydrogenase (LDH) levels were evaluated.

Results:

The total sample included 400 patients. Mean HGB, RBC, HCT and ESR were significantly higher in severe OSA group (p=0.05, p=0.05, p=0.02 and p=0.01, respectively). Mean MCV was significantly lower in subjects with OSA (p=0.01). RDW-CV showed association to the OSA severity (p=0.01), but RDW-SD was similar in OSA groups (p=0.07). Mean AHI, ESR and LDH were higher in obese patients (p=0.001, p=0.01, p=0.005, respectively). While mean HGB, RBC, HCT values were higher in obese cases (p=0.05, p=0.05, p=0.01), mean MCV was higher in nonobese individuals (p=0.01).

Conclusions:

Our results suggest that the severity of OSA can modify HGB and HCT levels in the complete blood count. Whether the magnitude of such a stimulation is high enough to cause secondary polycythemia needs further studies.

Keywords: obstructive sleep apnea, erythrocytosis, hemoglobin, red blood cell, hematocrit, body mass index.