Sleep‐mediated cognitive assessment and sleep architecture associations for real‐world diagnostic phenotyping of neurocognitive disorders

AbstractBackgroundSleep disorders precede cognitive deficits by an average of four years in Alzheimer’s disease, and disrupted sleep has been associated with worse cognitive performance. We examined the association of a novel sleep‐mediated cognitive assessment to sleep architecture in people with and without cognitive impairment, towards earlier diagnosis of cognitive impairment.MethodForty‐three participants from the Sleep & Memory Center at the Neurological Institute of Athens cohort underwent a comprehensive evaluation that included polysomnography and pre‐ and post‐ sleep cognitive assessments of a novel short term verbal memory test as well as phonemic fluency testing. We examined the correlation of sleep‐mediated cognitive performance to sleep metrics of total sleep time, NREM/REM sleep, as well as respiratory metrics of Apnea‐Hypopnea Index and oxygen saturation during sleep.ResultSleep‐mediated spontaneous recall and phonemic fluency metrics were not associated to sleep architecture metrics. Instead, sleep‐mediated cued recall and recognition was positively associated to REM metrics of sleep time and relative REM/NREM ratio (R > 0.39; p < 0.039). On individual metrics, pre‐sleep verbal learning was positively associated to total sleep time (R > 0.30; p<0.05) as well as a larger REM/NREM ratio (R 0.52; p = 0.003). Finally, higher levels of oxygen during sleep, especially REM sleep, were associated with better pre‐sleep verbal learning (R > 0.39; p < 0.44).ConclusionOur results on people across a spectrum of cognitive abilities suggest that sleep‐mediated cognitive performance is significantly affected by shorter sleep times, and to a large extent these effects are dependent to the integrity of REM sleep. It is possible that both late evening learning abilities and sleep‐mediated memory reflects a person’s cholinergic capacity, as represented in subsequent REM sleep.