1120 Inverse U-Curve Association Between Sleep Duration and Cognitive Performance Among Patients with Dementia: Findings From the Cretan Aging Cohort

Abstract

Abstract Introduction Previous research reports an inverse U-curve association between subjective sleep duration and cognition in elderly, while findings on objective sleep duration are inconsistent. Only one study found weak association between objective short sleep duration and cognition, mainly driven by demented elders. Our aim was to examine the non-linear associations between objective sleep duration and cognitive performance among community-dwelling patients with dementia. Methods A sub-sample of 46 patients with mild-to-moderate dementia(AD) [mean age: 80.3 (SD=5.6) years, 40% males] and 85 cognitively intact controls(NI) [mean age: 73.0 (SD=7.4) years, 37% males], were recruited from a large, population-based cohort [Cretan Aging Cohort] in the island of Crete, Greece of 3,140 older adults (≥60yrs). All participants underwent medical history/physical examination, extensive neuropsychiatric and neuropsychological evaluation, and 3-day 24-h actigraphy. Comparisons between AD and NI participants on sleep parameters and neuropsychological performance were made using ANOVA controlling for demographics. Associations between 24-TST, and age- and education-adjusted cognitive scores and Independent Activity of Daily Living Scale (IADL) scores were assessed using hierarchical, non-linear, regression models, controlling for confounders. Results Dementia patients had significantly longer 24-h total sleep time (24h-TST) (491.2±107.1 min vs. 444.6±88.5 min, respectively, p=0.027), as well as lower cognitive/IADL sores as compared to the NI group. Significant associations between objective sleep and various cognitive /IADL scores were found only among patients with dementia. Specifically, we found a negative curvilinear association between 24-h TST and IADL, episodic memory indices (AVLT Retention, autobiographic memory) and visuomotor coordination speed (Trail Making Test, Part A). Conclusion Our study showed an inverse U-curve association between objective sleep duration and daily function, memory, and executive function in patients with dementia. Possibly, sleep loss may lead to cognitive impairment, whereas, prolonged sleep may be an indicator of worse cognitive performance among patients with dementia. Support National Strategic Reference Framework (ESPA) 2007-2013, Program: THALES, University of Crete, title: “A multi-disciplinary network for the study of Alzheimer’s Disease” (Grant: MIS 377299).