P067 Sleepiness upon awakening in non-restorative sleep, insomnia, and healthy controls

Abstract Introduction Non-restorative sleep (NRS) is characterised by unrefreshing sleep despite normal sleep duration, in contrast to insomnia disorder (ID) which is characterised with difficulty with sleep initiation and maintenance. Both disorders have overlapping daytime impairments due to subjective sleep difficulties. We investigated whether morning sleepiness in NRS could be a marker that differentiates from ID and healthy controls. We hypothesise increased morning sleepiness in NRS compared to ID and healthy controls. Methods This case–control study involved a sample of 33 age- and sex-matched participants with NRS, ID, and healthy controls. Using high-density electroencephalography (HD-EEG) during a Karolinska Drowsiness Test, we measured objective sleepiness using alpha attenuation coefficient (AAC) and slowing ratio (SR). Subjective sleepiness was measured using the Karolinska Sleepiness Scale (KSS). Group differences were evaluated using a one-way ANOVA, topographical AAC and SR differences were assessed using cluster-mass permutation ANOVA, and general linear models were used to evaluate the association between KSS and HD-EEG measures. Results ID and NRS samples reported similar sleep architecture but poorer subjective sleep quality and greater fatigue than healthy controls. No group differences were found in subjective (p=.187) or objective (puncorrected = .080) sleepiness upon awakening. There was no significant association between subjective and objective sleepiness across groups, and no significant interaction. Discussion The symptom of unrefreshing sleep might not be associated with sleepiness. This highlights the need to explore other factors contributing to NRS, such as fatigue. Understanding these factors may aid in developing diagnostic criteria and effective treatments for NRS.