The relationship between sleep and cognitive performance on tests of pattern separation in older adults

Study objectives: Sleep disturbances are considered both a risk factor and symptom of dementia. The present research aimed to identify cognitive tests in which performance is associated with objective sleep quality or quantity, focusing on cognitive tests designed to evaluate the earliest cognitive changes in dementia. Methods: We recruited older adults (50 years of age or older) and remotely monitored their sleep patterns for 7 consecutive days using wrist actigraphy and sleep diaries. On day 7, participants completed a battery of cognitive tests, which included the Psychomotor Vigilance Task (PVT), the Prodromal Alzheimer's and Mild Cognitive Impairment battery from the Cambridge Neuropsychological Test Automated Battery (CANTAB), and the Mnemonic Similarity Task (MST), designed to tax pattern separation. The participants were also assessed with the Montreal Cognitive Assessment (MoCA). Results: The final sample included 34 participants (mean age: 65.56, SD: 9.57). There were significant correlations between objective total sleep time and PVT and MST performance. MoCA scores were correlated with performance on CANTAB and MST. Objective total sleep time also predicted MST performance when controlling for age and gender. Conclusions: Performance on cognitive tests designed to assess pattern separation are sensitive to older adults' objective sleep duration and the early cognitive changes associated with dementia. MST should be evaluated for potential use as a clinical trial outcome measure for sleep-promoting treatments in older adults.