Connecting the Dots: From Trait Vulnerability during Total Sleep Deprivation to Individual Differences in Cumulative Impairment during Sustained Sleep Restriction

1031 Editorial—Van Dongen Prominent discoveries in human sleep deprivation research since the turn of the millennium include (1) the cumulative, dose-response build-up of cognitive performance deficits across days of sustained sleep restriction1,2; and (2) the substantial, traitlike individual differences in vulnerability to cognitive impairment during acute total sleep deprivation (controlling for prior sleep history).3 These findings have spurred further research in laboratories around the world, yielding increasingly detailed knowledge about the effects on cognitive performance caused by total sleep deprivation, sustained sleep restriction, nap sleep, displaced sleep, recovery sleep, prior sleep history, interactions with circadian rhythmicity, and individual differences therein. Some of these effects have also been captured in quantitative models of fatigue and performance.4,5 Investigation of the temporal dynamics thereof has indicated that in schedules with sleep restriction to less than ~4 hours per day (which includes total sleep deprivation), performance deficits escalate progressively.5 Such schedules appear to be fundamentally more challenging to sustain than schedules with sleep restriction to more than ~4 hours per day, which also cause cumulative deficits1,2,6 but more gradually.5 Despite such progress in human sleep deprivation research, individual differences in responses to sleep loss have remained under-investigated and largely unexplained.7 In this issue of SLEEP, Rupp and colleagues8 contribute to filling this gap, by bridging between the findings of cumulative build-up of cognitive performance deficits across days of sustained sleep restriction and substantial individual differences in vulnerability to impairment during total sleep deprivation. In a within-subject research design, N = 19 carefully screened healthy volunteers (ages 18–39, 8 females) were studied in two conditions: (a) 2 nights and days of total sleep deprivation (63 hours of continuous wakefulness), and (b) 7 days of sleep restriction to 3 hours time in bed (04:00–07:00) each night. The two conditions were administered in randomized, counterbalanced order; were separated by 2 to 4 weeks; and were each preceded by 7 days with 10 hours time in bed (laboratory controlled) to satiate the need for sleep prior to the experimental interventions. During the sleep deprivation days and sleep restriction days of the two study conditions, subjects were continuously monitored, and cognitive performance was measured hourly. CogniEDITORIAL