Is polycythemia consistent with Obstructive Sleep Apnea (OSA)?

From the Guidelines

Yes, polycythemia is consistent with obstructive sleep apnea (OSA). Patients with OSA often develop secondary polycythemia as a compensatory response to chronic intermittent hypoxia that occurs during repeated apneic episodes during sleep [ 1 ]. When breathing stops temporarily during these episodes, oxygen levels in the blood drop, triggering the kidneys to produce more erythropoietin. This hormone stimulates the bone marrow to increase red blood cell production, resulting in elevated hemoglobin and hematocrit levels. The body essentially attempts to improve oxygen-carrying capacity to compensate for the recurrent nocturnal hypoxemia.

Key Points to Consider

• OSA is characterized by recurrent partial or complete collapse of the upper airway during sleep, affecting an estimated 9% of adult women and 24% of adult men [ 1 ].
• The condition has been associated with an increased risk of cardiovascular morbidity and mortality, with a relative risk of 1.7 [ 1 ].
• Finding polycythemia in a patient should prompt consideration of OSA as a potential underlying cause, particularly if other symptoms such as snoring, witnessed apneas, excessive daytime sleepiness, or morning headaches are present.
• Treatment of the underlying OSA with continuous positive airway pressure (CPAP) therapy or other appropriate interventions typically leads to normalization of the red blood cell count over time as the chronic hypoxic stimulus is removed [ 1 ].

Diagnosis and Treatment

• Screening for OSAS can be performed using the Berlin Questionnaire and daytime sleepiness can be assessed by the Epworth Sleepiness Scale and overnight oximetry [ 1 ].
• Definitive diagnosis often requires polysomnography, usually during a night in a sleep laboratory during which multiple physiological variables are continuously recorded [ 1 ].
• Continuous positive airway pressure is the gold-standard therapy and reduces CV mortality and events [ 1 ].

From the Research

Relationship Between Polycythemia and OSA

• The relationship between polycythemia and obstructive sleep apnea (OSA) is complex and has been studied in various research papers 2, 3, 4, 5.
• A study published in 2015 found that polycythemia is not commonly seen in patients with sleep apnea syndrome, and only 1 male patient with severe OSA (0.3%) had clinically significant polycythaemia 2.
• In contrast, a 2022 study found that the prevalence of polycythemia was significantly higher in patients with overlap syndrome (OVS), where OSA and chronic obstructive pulmonary disease (COPD) coexist, compared to patients with COPD alone 3.
• Another study published in 2017 found that OSA severity was not associated with hematocrit or clinically significant erythrocytosis, but rather with hypoxemia as measured by awake and mean nocturnal oxygen saturation 4.
• A 2020 study found that OSA was associated with polycythemia in hypogonadal men on testosterone replacement therapy, with an odds ratio of 2.09 [95% CI 1.17,3.76] 5.

Factors Influencing the Relationship

• The relationship between polycythemia and OSA may be influenced by various factors, including:
  • Severity of OSA: A 2022 study found that the prevalence of polycythemia increased with OSA severity 3.
  • Hypoxemia: A 2017 study found that hypoxemia, as measured by awake and mean nocturnal oxygen saturation, was associated with hematocrit and erythrocytosis 4.
  • Testosterone replacement therapy: A 2020 study found that OSA was associated with polycythemia in hypogonadal men on testosterone replacement therapy 5.
  • Body mass index (BMI): A 2020 study found that BMI was strongly associated with OSA in hypogonadal men on testosterone replacement therapy 5.