Obstructive sleep apnea (OSA) occurred more frequently in men with idiopathic intracranial hypertension (IIH) compared with men without IIH, regardless of body mass index (BMI), according to study findings published in the Journal of Neuro-ophthalmology.
Researchers at the University of Toronto in Canada conducted a prospective, case-control study of 11 men with IIH compared with 10 healthy, age- and BMI-matched control participants to assess the rate of hypercapnia during polysomnography (PSG) and the relationship between hypercapnia and OSA rate and severity. Seven of the 11 men with IIH and 4 of the 10 control participants had BMIs over 30 kg/m2. The mean age was 41.9 years.
The men underwent overnight PSG with continuous oxygen and carbon dioxide monitoring. The researchers collected and analyzed data on OSA diagnosis, rate of hypercapnia, rate of hypoxia, and the apnea hypoxia index (AHI), comparing the 2 groups.
All of the men with IIH who had BMIs greater than 30 kg/m2 (7 of 7) were diagnosed with OSA, while 2 of the 4 control participants with BMIs over 30 kg/m2 were diagnosed with OSA. OSA diagnosis was two times more prevalent among the men with IIH (9 of 11) compared with control participants (4 of 10).
In comparison, around 50% of the men with IIH with BMIs less than 30 kg/m2 (2 of 4) and 33% (2 of 6) of control participants with BMIs less than 30 kg/m2 received a diagnosis of OSA.
Therefore, BMI significantly predicted OSA severity (P =.023) and total AHI (P =.042).
The rate of hypercapnia did not differ between groups, leading to the conclusion that hypercapnia did not play a causative role in the pathogenesis of IIH.
Additionally, the relationship between OSA and IIH is unknown, although scientists hypothesize three potential mechanisms for this connection. One suggests that the high blood pressure caused by OSA increases intracranial pressure. Another theorizes that mechanical airway obstruction in OSA reduces cerebral venous drainage, which potentially increases the intracranial pressure. The third theory postulates that the hypoxia and hypercapnia caused by OSA results in cerebral vasodilation, thus leading to increased intracranial pressure.
“… BMI is the strongest predictor of OSA diagnosis and severity,” the researchers stated. “OSA is more common in men with IIH compared with men without IIH, even at lower BMI.”
They concluded, “Based on these data, we recommend that all men with the diagnosis of IIH should undergo PSG study.”
Study limitations included the relatively small sample size due to the rarity of idiopathic ICH among men and lack of complete data on hypercapnia for all study participants.
Kabanovski A, Chan A, Shapiro C, Margolin E. Obstructive sleep apnea in men with idiopathic intracranial hypertension: A prospective case-control study. J Neuroophthalmol. Published online November 1, 2022. doi:10.1097/WNO.0000000000001734