From the Guidelines
Elevated hemoglobin and hematocrit can suggest sleep apnea but are not definitive diagnostic markers. Sleep apnea causes intermittent drops in oxygen levels during sleep, and the body may respond by increasing red blood cell production (erythrocytosis) to improve oxygen-carrying capacity. This compensatory mechanism can lead to elevated hemoglobin and hematocrit levels, particularly in severe or long-standing cases. However, many other conditions can also cause these laboratory abnormalities, including dehydration, lung disease, heart disease, living at high altitude, smoking, and certain bone marrow disorders. If elevated hemoglobin and hematocrit are found, especially alongside symptoms like excessive daytime sleepiness, loud snoring, witnessed breathing pauses during sleep, morning headaches, or difficulty concentrating, sleep apnea should be considered.
Key Considerations
- The most recent study 1 emphasizes the importance of proper diagnosis and treatment of obstructive sleep apnea syndrome (OSAS) to reduce morbidity and mortality.
- According to the American Academy of Sleep Medicine 1, the diagnosis of OSA involves measuring breathing during sleep, and a comprehensive sleep evaluation is essential to ensure appropriate diagnostic testing.
- A sleep study (polysomnography) is necessary to confirm the diagnosis of sleep apnea, as it measures breathing patterns, oxygen levels, and other parameters during sleep 1.
- Treatment options for sleep apnea may include continuous positive airway pressure (CPAP) therapy, oral appliances, lifestyle modifications like weight loss, or in some cases, surgery 1.
Diagnostic Approach
- A home sleep apnea test (HSAT) can be used for the diagnosis of OSA in patients for whom in-laboratory PSG is not available or possible due to immobility, safety, or critical illness 1.
- The Apnea Hypopnea Index (AHI) and respiratory disturbance index (RDI) can be used to determine the severity of OSA, with AHI categorized as mild (5 ≤ AHI < 15/h), moderate (15 ≤ AHI < 30/h), and severe (AHI ≥ 30/h) 1.
- Other surrogate parameters like hypoxic burden, hypoxia load, obstruction severity, or phenotypes based on symptoms and comorbidities should be considered together with AHI in the disease management and treatment decision-making processes 1.
From the Research
Association between Elevated Hemoglobin and Hematocrit and Sleep Apnea
- Elevated hemoglobin and hematocrit levels have been observed in patients with obstructive sleep apnea (OSA) 2, 3, 4.
- A meta-analysis found that the prevalence of polycythemia was higher in patients with severe OSA compared to those with mild-to-moderate OSA 2.
- Studies have shown that continuous positive airway pressure (CPAP) treatment can reduce hemoglobin and hematocrit levels in patients with OSA 2, 4.
Predictive Value of Hematocrit Levels
- Research suggests that intermittent nocturnal hypoxemia during episodes of apnea is associated with minor elevations in hematocrit value, but these elevations are unlikely to be useful as markers of hypoxic stress associated with sleep apnea 3.
- Hematocrit levels have been found to decrease significantly after CPAP treatment in patients with OSA, particularly in those with mild and severe cases 4.
Hematological Evaluation in OSA
- Red blood cell distribution width (RDW), mean platelet volume (MPV), and platelet distribution width (PDW) have been recognized as biomarkers of cardiovascular morbidity/mortality in OSA patients 4.
- A prospective study found that RDW values were associated with OSA severity and that red cell and platelet parameters changed significantly after CPAP treatment 4.