1047 Sleep Fragmentation Predicts Diminished Processing Speed in Non-demented Elderly from the Cretan Aging Cohort

Abstract Introduction Processing speed is an early index of cognitive decline in elderly. Also, sleep quality predicts memory deficits in this age group. However, the relationship between sleep fragmentation and processing speed remains controversial. Our aim was examine the longitudinal associations between sleep quality and processing speed in non-demented community dwelling elderly. Methods A sub-sample of 148 participants diagnosed with Mild Cognitive Impairment (MCI;n=79) or cognitively non-impaired (CNI;n=69) from the Cretan Aging Cohort, a large population-based cohort of 3,140 older adults (60 years; baseline) were followed-up 8 years later (follow-up). Mean age at baseline was 74.9±6.33 and 70.4 ±6.24 years for MCI and CNI persons. Processing speed was assessed based on age and education adjusted z-scores of the Symbol Digit Modality Test. Sleep fragmentation (wake after sleep onset; WASO) was assessed using a 3-day actigraphy at baseline and follow-up. Change between the two time points was calculated using paired sample t-tests. The direct and indirect effects of baseline WASO on subsequent processing speed after controlling for sociodemographic covariates were estimated using panel models in AMOS. Results Average WASO among MCI and CNI participants was 80.6±41min and 72.3±31.2min; p=0.1 and 75.7±34.8min and 59.3±20.6min; p 0.001 at baseline and follow-up, respectively. Average processing speed decreased between the two measurement points (CNI: 0.23±0.97 and -0.40±1.04; p 0.001 and MCI: -0.75±0.60 and -1.09±0.72; p 0.001 at baseline and follow-up, respectively). Baseline WASO directly predicted processing speed (β=-0.201; p=0.04) among MCI persons, while WASO at follow-up fully mediated the relationship between baseline WASO and subsequent processing speed (β=-0.098; p=0.004) in the CNI group. Conclusion Sleep fragmentation predicts diminished processing speed among non-demented elderly. Given the significance of processing speed on cognitive function, interventions improving sleep quality in elderly may prevent/delay cognitive decline. 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 377299 HELLENIC 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: HFRI-FM17-4397