075 Systematic Individual Differences in Vulnerability to Sleep Inertia

Abstract Introduction Sleep inertia (SI), the transient grogginess and disorientation that occurs upon awakening, may be particularly problematic in on-call operations require safety-sensitive time-critical action, such as healthcare emergency response. The magnitude of SI is determined by multiple factors, including sleep history, anecdotal evidence suggests individuals differ considerably susceptibility to impairment from SI. Methods As part a larger study investigating individual differences neurobehavioral impairment, N=21 healthy adults (aged 21–38y; 9 females) completed three laboratory-based testing sessions, each preceded baseline sleep. Baseline nightly at-home opportunities during week prior were either 12h (extended) or 6h (restricted); two sessions involved extension one restriction randomized, counterbalanced order. ended at 10:00, whereupon subjects 60min test battery, which began with Karolinska Sleepiness Scale (KSS). battery was repeated every 2h throughout sessions. Results A nonlinear mixed-effects regression, controlling for restriction/extension session number, used estimate subjective immediately awakening sleep, measured KSS scores, exponential dissipation rate effect relative scores later day (12:00-20:00). Following extension, associated 1.82±0.59 score increase (p=0.006), subsequently dissipated level 4.80±0.65 2.98±0.29 (p=<0.001) day. restriction, 1.58±0.58 (p=0.014), 5.39±0.63 3.80±0.30 took ~45min dissipate negligible based on time constant 23.6±15.8min. Importantly, there substantial, systematic SI, between-subjects standard deviation 1.15±0.42 points (ICC=0.51, F=19.5, p<0.001). Conclusion We observed sizeable, sleepiness due inertia. To what degree these predict objective performance deficits remains investigated. Support (if any) NASA grant NAG9-1161 CDMRP W81XWH-20-1-0442