Is obstructive sleep apnea associated with erythrocytosis? A systematic review and meta‐analysis

OBJECTIVE: The aim of this systematic review and meta‐analysis was to investigate the association between obstructive sleep apnea (OSA) and erythrocytosis. METHODS: The PubMed, Web of Science, and Cochrane Library databases were searched for articles examining hematocrit values in patients with OSA and control individuals published till September 1, 2021. The pooled standardized mean difference (SMD) with 95% confidence interval (CI) was calculated, and subgroup analyses were performed. RESULTS: Eleven eligible studies with a total of 4608 patients with OSA were included in this meta‐analysis. Pooled outcomes revealed that hematocrit values were significantly higher in patients with OSA than in controls (SMD, 0.19; 95% CI, 0.08–0.29; p < .01). When studies were stratified by disease severity, the significant differences in hematocrit values between patients and controls were only observed in the severe OSA group (SMD, 0.34; 95% CI, 0.08–0.59; p < .01), but not in the mild and moderate OSA groups. In subgroup analyses according to sex and publication year, significant differences in hematocrit values between patients and controls remained stable in studies with only female patients (SMD, 0.25; 95% CI, 0.12–0.38; p < .01) and in studies published after 2012 (SMD, 0.17; 95% CI, 0.06–0.28, p < .01). CONCLUSION: Our meta‐analysis revealed that the hematocrit value was significantly increased in patients with OSA, particularly in severe patients, compared with that in controls. However, the elevation was modest, and the hematocrit value is expected to be within the normal range in patients with OSA. These data suggest that OSA leads to slight increases in hematocrit but does not cause clinically significant erythrocytosis.