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Hematocrit levels and presence of erythrocytosis do not appear to be associated with obstructive sleep apnea (OSA) as measured by the apnea-hypopnea index (AHI), according to research presented at SLEEP 2017, the 31st Annual Meeting of the Associated Professional Sleep Societies, held June 3-7 in Boston, Massachusetts.
Researchers from the Department of Medicine at Stanford University in Palo Alto, California, reviewed data of 1604 veterans who exhibited OSA based on the AHI. A prospective sleep questionnaire was used to record self-reported habits, demographics, medical comorbidities, and medication use. Laboratory information was obtained using an electronic medical record.
Of the 1604 patients, 92% were male (age, 57.6±13.4 years), with 48.2% having moderate-severe OSA. Only 7.4% of patients had a hematocrit ≥48%, with only 1.6% having clinical erythrocytosis.
In a multivariate analysis testing the association between AHI and hematocrit, factors associated with higher hematocrit levels (≥48%) were as follows: awake hypoxemia (odds ratio [OR], 4.7; P <.001), nocturnal hypoxemia (OR, 1.8; P =.021), diabetes mellitus (OR, 0.40; P =.002), and testosterone therapy (OR, 2.9; P =.001).
In addition, OSA, specifically severe OSA, was associated with nocturnal hypoxemia (OR, 7.4; P <.001), but awake hypoxemia (OR, 5.2; P <.001) and chronic obstructive pulmonary disease (OR, 2.6; P <.001) were less predictive of nocturnal hypoxemia. However, only 8% of patients with moderate-severe OSA who had nocturnal hypoxemia had erythrocytosis.
In patients with suspected or confirmed OSA, clinically significant erythrocytosis appears uncommon. In addition, instead of hematocrit levels and presence of erythrocytosis, awake and nocturnal hypoxemia were associated with OSA as measured by AHI.
“Nocturnal oximetry may provide diagnostic utility in the evaluation of unexplained secondary erythrocytosis[, and polysomnography] may be warranted in those with unexplained nocturnal hypoxemia,” noted the researchers.
Reference
Nguyen C, Holty J. Obstructive sleep apnea and secondary erythrocytosis: analysis from a large cross-sectional observational study. Presented at: SLEEP 2017: 31st Annual Meeting of the Associated Professional Sleep Societies; June 3-7; Boston, MA. Abstract 1023.
