Relationship Between Obstructive Sleep Apnea and Autonomic Failure

To investigate daytime autonomic dysregulation in patients with obstructive sleep apnea (OSA).

This retrospective study was conducted at Brigham and Women's Faulkner Hospital Autonomic Laboratory and evaluated adult patients with a history of orthostatic intolerance and sleep disturbances who completed autonomic testing (deep breathing test, Valsalva maneuver, tilt test) and polysomnography between 2018 and 2024. The Quantitative Scale for Grading of Cardiovascular Autonomic Reflex Tests scoring instrument graded autonomic tests and skin biopsies for the assessment of small fibers. The apnea-hypopnea index was used to assess OSA severity.

In total, 138 patients were evaluated in this study. Subjects with OSA (43 with mild and 29 with moderate/severe OSA) were compared with 66 subjects without OSA. Age, body mass index, and the prevalence of hypertension increased with the severity of sleep apnea. At least moderate autonomic failure was identified in 60% of patients without OSA and in 78% of those with OSA. Autonomic failure score was proportional to the severity of OSA (autonomic failure scores: no OSA 4.2 ± 2.54, mild OSA 5.44 ± 3.41, moderate/severe OSA 8.1 ± 4.3, P < 0.001). Small fiber neuropathy was found in 41.8% of patients without OSA and in 70.8% of patients with moderate/severe OSA.

Autonomic failure associated with small fiber autonomic neuropathy is common in patients with OSA, and the degree of autonomic failure is proportional to the severity of sleep apnea. Autonomic failure can be an additional risk factor contributing to the cardiovascular complications observed in OSA.