By placing nine healthy participants on a 20-hour "day" during a 32-day inpatient protocol, researchers were able to separate the impact of chronic short sleep from any extended wakefulness. The participants were restricted to 4.67 hours of sleep and 15.33 hours of wakefulness for each 20-hour "day"; this corresponds to approximately 5.5 hours of sleep on a 24-hour day. Eight healthy controls were allowed to sleep 6.67 hours and have 13.33 hours of wakefulness per 20-hour "day", the equivalent of sleeping 8 hours in a 24-hour day. As 15.33 hours of wakefulness is not considered extended wakefulness, but 4.67 hours of sleep is considered short sleep, any performance impairments were considered due to the short sleep itself.
‘Chronic short sleep, independent of associated extended wakefulness, causes cognitive impairments yet does not alter a person's self-reported alertness.’
The researchers found that participants with restricted sleep had a fivefold increase in attention lapses and doubled neurobehavioral reaction time compared to controls, yet there was no relationship between an individual's self-reported alertness or sleepiness and their vigilant performance. This means that even though individuals were impaired as a result of chronic sleep restriction, they did not notice these impairments. Further, participants on the restricted sleep schedule worsened in these cognitive tasks over the 32-day protocol, suggesting that people are not able to adapt to chronically restricted sleep.
"We have shown that sleep in itself is important," said Klerman. "People cannot learn to live on insufficient sleep and they may not be aware of their reduced cognitive abilities. More so, our study suggests the importance of longer episodes of sleep, rather than a 'split sleep' schedule, though further evidence would be needed to test this directly."
Source: Eurekalert
