Obstructive sleep apnea (OSA) has been associated with a broad range of neurocognitive difficulties. The current view is that the neurocognitive impairment in OSA is due to the adverse effects of sleep fragmentation and/or intermittent hypoxia. The overall picture of cognitive deficits in OSA is complex. On balance, there appears to be negative effects of OSA on cognition, most likely in the domains of attention/vigilance, verbal and visual delayed long-term memory, visuospatial/constructional abilities, and executive dysfunction. Continuous positive airway pressure (CPAP) is the most effective and widely used treatment of OSA. In the majority of studies of OSA patients treated with CPAP, attention/vigilance improved, but changes in global functioning, executive functioning, and memory improved in about half of the studies. This may be due, in part, to variability in study design and sampling methodology across studies.
Structural volume changes have been demonstrated in brain regions of OSA patients including areas that regulate memory and executive function (e.g., frontal cortex, anterior cingulate, and hippocampus). Growing evidence suggests that the OSA-related changes in brain morphology may improve with CPAP treatment. Neuroimaging studies performed during cognitive testing have provided insight into CPAP's effect on function of neuroanatomical circuits in the brain. Although neuroimaging can provide important insights into the structural and functional differences associated with OSA, one of the challenges is to interpret the findings in light of comorbid conditions that also cause neural injury. The purpose of this article is to provide a narrative review of the publications on cognition and neuroimaging in OSA before and after CPAP treatment.
