Prevalence of elevated hemoglobin and hematocrit levels in patients with obstructive sleep apnea and the impact of treatment with continuous positive airway pressure: a meta-analysis.
Level 3 - non-randomized controlled study
Meta-analysis of observational studies and single-arm intervention trials without randomized controls
PubMed 35962574 · doi:10.1080/16078454.2022.2109346
What was done
MEDLINE, Embase, and Cochrane were searched for studies of adult patients with obstructive sleep apnea (OSA) reporting hemoglobin or hematocrit levels. Meta-analyses were performed to estimate the pooled prevalence of secondary polycythemia (overall and by OSA severity) across seven studies, and to determine changes in hemoglobin and hematocrit following continuous positive airway pressure (CPAP) treatment across ten single-arm trials.
What was found
In seven studies including 3,654 patients, overall polycythemia prevalence was 2% (95% CI 1-4%), with 2% (95% CI 1-3%) in mild-to-moderate OSA and 6% (95% CI 3-12%) in severe OSA. In ten single-arm trials with 434 patients, CPAP treatment reduced hemoglobin by 3.76 g/L (95% CI -4.73 to -2.80 g/L). In ten single-arm trials with 356 patients without baseline polycythemia, CPAP treatment reduced hematocrit by 1.1% (95% CI -1.4 to -0.9%).
Why it matters
This review quantifies the clinical burden of secondary polycythemia across OSA severity strata and confirms that CPAP therapy produces modest, measurable reductions in red blood cell indices.
Limits
CPAP efficacy estimates relied entirely on single-arm uncontrolled trials rather than randomized controlled trials. Hematocrit response was only reported in patients without baseline polycythemia. The authors note prevalence is likely underestimated due to changes in diagnostic criteria in 2016. Confounders such as smoking, CPAP adherence, and duration of therapy were not detailed in the abstract.
Cited by
- context Elevated hematocrit and hemoglobin in physically unfit, non-exercising individuals is a common clinical indicator of sleep apnea.
- supports CPAP therapy in patients with sleep apnea lowers elevated hematocrit and hemoglobin levels.