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

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.

Disconnection Between Self-Reported and Objective Cognitive Impairment in Obstructive Sleep Apnea.

STUDY OBJECTIVES: Recent studies show that obstructive sleep apnea (OSA) is a possible contributor to abnormal cognitive decline in older adults. These new observations create the need to identify older adults with OSA who are at risk of the developing dementia if not treated. This study's goal was to verify whether self-reported cognitive complaints could become a useful tool to screen for objective cognitive deficits in late middle-aged and older adults with OSA. METHODS: Fifty-seven participants with OSA with an apnea-hypopnea index (AHI) ≥ 15 events/h (3% or arousal) and aged between 55 and 85 years were compared to 54 participants in a mild/non-OSA group on their ability to evaluate their objective cognitive functioning. They underwent overnight polysomnography followed by a comprehensive neuropsychological assessment. We recruited a similar proportion of participants with mild cognitive impairment (MCI) in both groups (OSA: 36.8%; mild/non-OSA: 35.2%). They filled out questionnaires assessing mood, sleep, and cognition. Group (OSA versus mild/non-OSA) × cognitive status (MCI versus non-MCI) analyses of variance were performed on cognitive complaint questionnaires. RESULTS: We found that among participants without objective cognitive deficits, participants in the OSA group reported more cognitive complaints compared to those in the mild/non-OSA group. Among participants with objective cognitive deficits, those in the OSA group reported less cognitive complaints compared to those in the mild/non-OSA group. CONCLUSIONS: Participants with OSA and MCI were less aware of their deficits compared to those in the mild/non-OSA group, possibly reflecting a distinctive OSA-associated cognitive impairment. Our results underscore the importance of referring patients with OSA for a comprehensive neuropsychological assessment when an abnormal cognitive decline is suspected.