P047 Slow Wave Dynamics in Mild Cognitive Impairment compared with Age Matched Controls: A High Density EEG study.

INTRODUCTION: Slow wave activity during non-rapid eye movement (NREM) sleep has been linked with memory consolidation in healthy older adults. To date, there has been limited research in mild cognitively impaired populations, particularly looking across the whole brain using high density EEG. We aimed to determine if the dynamics of slow wave activity (delta power) during the first NREM sleep cycle differ between patients with mild cognitive impairment (MCI) and healthy older adults. METHODS: Participants were assessed for MCI by a panel of neuropsychologists and clinicians. They underwent full polysomnography including high-density EEG (256 electrodes). We computed the delta power (0.5-4.5Hz) for each NREM cycle and slope between sleep onset and the peak of delta in the first NREM sleep cycle (rise-rate) which were compared between groups using t-tests. RESULTS: 17 older adults with MCI and 21 older healthy controls were assessed. The mean delta power in the first NREM cycle did not differ between MCI and controls across the whole brain, but the global rise-rate (1/min) of MCI and controls was 0.0015 and 0.0032 respectively (t-value -2.35, p=0.025). DISCUSSION: Global slow wave dynamics in the first NREM period appear to be altered in patients with MCI compared with age-matched controls. The gentler slope of rise-rate to the first delta peak in MCI patients than in healthy controls may indicate the dysfunction of sleep homeostasis in MCI patients. Regional slow wave dynamics, ultra-low frequency delta (0.25-1Hz), and associations with sleep dependent memory consolidation will further be explored.