Evaluation of Cerebrovascular Reactivity in Subjects with and without Obstructive Sleep Apnea

Both obstructive sleep apnea (OSA) and altered cerebrovascular reactivity (CVR) are associated with increased stroke risk. Nevertheless, the incidence of abnormal CVR in patients with OSA is uncertain due to the high variability in the way CVR is measured both within and between studies. We hypothesized that a standardized CVR with a consistent vasoactive stimulus and cerebral blood flow (CBF) measure would be reduced in patients with severe OSA compared with healthy controls.This was a prospective study in which subjects with and without OSA were administered a standardized hypercapnic stimulus, and CBF was monitored by blood oxygen level-dependent magnetic resonance signal changes, a high space and time resolved surrogate for CBF.Twenty-four subjects with OSA (mean age 45.9 years, apnea-hypopnea index [AHI] 26.8 per hour) and 6 control subjects (mean age 42.8 years, AHI 2.4 per hour) were included. Compared with controls, subjects with OSA had a significantly greater whole brain (.1565 versus .1094, P = .013), gray matter (.2077 versus .1423, P = .009), and white matter (.1109 versus .0768, P = .024) CVR, respectively.Contrary to expectations, subjects with OSA had greater CVR compared with control subjects.