Sleep regulation and waking function: Lessons from chronic versus acute sleep deprivation studies

Abstract

In modern societies, many humans are exposed to a combination of acute and chronic sleep loss and circadian misalignment. Whereas it is known that these factors can impair alertness and cognitive performance, the contribution of each of them as well as their interaction when they operate together, are largely unknown. We therefore subjected young healthy individuals in the lab to a 3-week forced desynchrony protocol during which they were exposed to a long sleep-wake cycle (42.85 h) and a reduced sleep:wake ratio of 1:3.3. Over three weeks, the protocol therefore induced an increasing chronic sleep loss while allowing extended wake and sleep episodes to occur at all circadian phases. We quantified the occurrence of spontaneous attentional failures by hours awake (acute sleep loss), by study week (chronic sleep loss), and by circadian phase derived from plasma melatonin. It was found that chronic sleep loss 1) speeds up the rate at which inadvertent attentional failures accumulate during a wake episode, and 2) amplifies the circadian variation in attentional failures. Thus, acute and chronic sleep loss in combination with circadian phase should be considered as distinct factors that interact in a non-additive way to affect waking function. In another series of studies we compared short and long sleepers and identified trait-like individual differences in the tolerance of acute and chronic sleep loss.