0636 Objective sleep as a predictor of cognitive decline among non-demented elderly: preliminary results from the Cretan Aging Cohort
Authors: Basta Maria , Skourti Eleni , Zampetakis Alexandros , Alexopoulou Christina , Ganiaris Andronikos , Aligizaki Marina , Simos Panagiotis , Vgontzas Alexandros 
Published: May 2022

Abstract

Introduction
Sleep disturbances have been linked with cognitive decline and previous cross-sectional have shown that long sleep duration is a marker of disease severity in patients Mild Cognitive Impairment (MCI) and Dementia.Our aim was to examine the longitudinal associations between sleep quantity and quality indices and cognitive progression in non-demented community-dwelling elderly.

Methods
A sub-sample of 62 participants (72.6% females) were recruited from a large population-based cohort in the island of Crete, Greece of 3,140 older adults (&gt;60yrs). Participants were followed-up 8 years later (phase III). All participants underwent neuropsychiatric/neuropsychological evaluation (phases II & III) and a 3-day 24h actigraphy (phase II).Participants were diagnosed as CNI(N=38) and MCI(N=24) during phase II, and CNI (N=22), MCI (N=27) and Dementia (N=13) during phase III. On follow-up, 28 participants progressed to a cognitively declined diagnosis compared to phase II (deteriorated group), while 34 did not (non-deteriorated group). Objective sleep variables at phase II were compared between the deteriotated/non-deteriorated groups using ANCOVA controlling for confounders. Also, differences in neuropsychological testing scores (phase II- phase III) were calculated and associations of differences with sleep variables were examined using partial correlation models controlling for confounders.

Results
The deteriorated group compared to non-deteriorated had significantly longer night total sleep time (TST) (442±72.6min vs. 407±53.6min, p=0.033), 24h-TST (484±8.9min vs. 434±66.4min, p=0.008), night time in bed (TMB) (537±78.7min vs. 497±62.7min, p=0.03), and 24h-TMB (603±85min vs. 539±85min, p=0.005). Episodic memory worsening was moderately correlated with night TST (r=.316), night and 24h-TMB (r=.526, and r= .442 respectively), wake time after sleep onset (r=.351), and average duration of night awakenings (r=.405). Immediate episodic memory recall decline was positively correlated with night TMB (r=.338).

Conclusion
Preliminary results from the Cretan aging cohort indicate that almost half of the participants deteriorated cognitively in 8 years and this decline was predicted by objective sleep duration at baseline. Long sleep at baseline may predict deterioration of clinical cognitive status in non-demented elderly at follow-up. It appears that prolonged objective sleep duration and time in bed are novel and clinically useful prognostic factors of cognitive deterioration in elderly with or without cognitive deficits.

Support (If Any)
National Strategic Reference Framework (NSRF) - Research Funding Program: THALES entitled “UOC-Multidisciplinary network for the study of Alzheimer’s Disease” Grant Cod: MIS 377299HELLENIC FOUNDATION FOR REASEARCH AND INNOVATION (HFRI)- Research Funding Program: ELIDEK entitled “Sleep Apnea (OSA) and poor sleep as Risk Factors for decreased cognitive performance in patients with Mild Cognitive Impairment: the Cretan Aging Cohort (CAC)”, Grant Cod: HFR1-FM17-4397