0149 Perception of Prior Sleep-Wake State upon Abrupt Exogenous Awakenings

Abstract Introduction The period immediately following an awakening is characterized by sleepiness, poor cognitive performance, and disorientation known as sleep inertia. In an exploratory analysis, we investigated the accuracy of perceived sleep-wake state after being abruptly awoken. Methods Thirty-six participants (18 female; 26.6 years ± 6.1) slept in their own homes and were called on a pre-set cell phone three times: twice during their habitual sleep period (approximately 45 min and 135 min after habitual bedtime) and once at their habitual waketime the next morning (n = 108 awakenings). Sleep stage prior to waking was measured by polysomnography. Researchers observed participants remotely via an infrared camera. Participants were asked whether they thought they had been ‘asleep’, ‘awake’, or ‘unsure’ immediately prior to receiving the phone call. Results Polysomnography determined that participants were asleep prior to the call for 88.0% (n = 99) of the awakenings (Wake: 8.3%, N1: 10.2%, N2: 27.8%, N3: 38.9%, REM: 11.1%, Undefined: 3.7%). Participants were asleep for all instances in which the self-perceived state prior to awakening was ‘asleep’. When state was self-perceived as ‘awake’ or ‘unsure’, participants were awake 25% of the time and in N3 sleep 19% of the time (sensitivity: 71.6%; specificity: 100%). One-fifth (n = 7) of the cohort were unable to correctly identify being asleep on multiple awakenings. Conclusion Participants correctly identified themselves as being asleep with moderately low sensitivity, but high specificity. Interestingly, even participants in deep sleep stages (N3) sometimes perceived themselves to be awake before the call. A portion of participants were consistently poor at identifying being asleep. These misperceptions of sleep-wake state upon awakening may contribute to the disorientation experienced during the sleep inertia period and may be influenced by individual differences. Although the uneven distribution of sleep-wake states in this sample limits us to descriptive statistics, our exploratory analysis suggests that a systematic assessment of perception during the sleep-wake transition and its subsequent effect on alertness, cognitive performance, and decision making is warranted. Support (if any) Naval Postgraduate School, via the Naval Medical Research Center's Naval Advanced Medical Development Department (MIPR N3239820WXHN007). NASA Airspace Operations and Safety Program, System-Wide Safety.