Obstructive sleep apnea during REM sleep and daytime cerebral functioning: A regional cerebral blood flow study using high-resolution SPECT

Abstract

Obstructive sleep apnea (OSA) predominantly during rapid eye movement (REM) sleep may have impacts on brain health, even in milder OSA cases. Here, we evaluated whether REM sleep OSA is associated with abnormal daytime cerebral functioning using high-resolution single-photon emission computed tomography (SPECT). We tested 96 subjects (25 F, age: 65.2 ± 6.4) with a wide range of OSA severity from no OSA to severe OSA (apnea-hypopnea index: 0-97 events/h). More respiratory events during REM sleep were associated with reduced daytime regional cerebral blood flow (rCBF) in the bilateral ventromedial prefrontal cortex and in the right insula extending to the frontal cortex. More respiratory events during non-REM (NREM) sleep were associated with reduced daytime rCBF in the left sensorimotor and temporal cortex. In subjects with a lower overall OSA severity (apnea-hypopnea index<15), more respiratory events during REM sleep were also associated with reduced daytime rCBF in the insula and extending to the frontal cortex. Respiratory events that characterized OSA during NREM versus REM sleep are associated with distinct patterns of daytime cerebral perfusion. REM sleep OSA could be more detrimental to brain health, as evidenced by reduced daytime rCBF in milder forms of OSA.

Keywords: Functional neuroimaging; perfusion; rapid eye movement-predominant obstructive sleep apnea; single-photon emission computed tomography; sleep-disordered breathing.

Figure 1.

Daytime brain perfusion patterns associated with OSA during REM versus NREM sleep. In the complete sample representing all OSA severities (n = 96, AHI from 0 to 97, model 1), reduced daytime rCBF is associated with (a) a higher REM-AH in the bilateral ventromedial prefrontal cortex and right insula extending to the frontal cortex; (b) a higher NREM-AH in the left sensorimotor and lateral temporal cortex. Regressions model were between REM-AH and daytime rCBF, adjusted for age, total sleep duration and NREM-AH (a); and between NREM-AH and daytime rCBF, adjusted for age, total sleep duration and REM-AH (b). Statistical analyses were performed on every voxel of gray matter. Significant regions of abnormal rCBF were identified when single voxels showed a significant regression with the OSA variable (statistical threshold at p < 0.001) and when these were surrounded by a cluster of ≥100 voxels with rCBF values that behave similarly. Similar regions of daytime hypoperfusion were observed when REM-AHI and NREM-AHI were used instead of REM-AH and NREM-AH. rCBF: regional cerebral blood flow; NREM: non-rapid eye movement sleep; REM: rapid eye movement sleep; AH: apneas + hypopneas; AHI: apnea–hypopnea index; OSA: obstructive sleep apnea.