Mixed
Chronically restricting sleep to 6 hours or less per night for 14 consecutive days produces cumulative cognitive performance deficits equivalent to 1-2 nights of total sleep deprivation, despite subjects remaining largely unaware of their declining performance.
If you consistently sleep 6 hours or less, your cognitive performance (reaction time, memory, decision-making) will degrade daily over two weeks to the level of someone who has been awake for 48 hours. You will not feel this decline because your subjective sense of sleepiness plateaus early. To maintain peak cognitive function, you must prioritize 7-8 hours of sleep, as 'getting used to' less sleep is a dangerous illusion that impairs your performance without your awareness.
Chronic restriction of sleep to 6 h or less per night produced cognitive performance deficits equivalent to up to 2 nights of total sleep deprivation... Sleepiness ratings suggest that subjects were largely unaware of these increasing cognitive deficits
Why this rating
Randomized controlled trial with strict laboratory monitoring, large sample size (n=48), and sophisticated statistical modeling (mixed-effects regression).
Source
The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology From Chronic Sleep Restriction and Total Sleep Deprivation
Hans P. A. Van Dongen et al. · SLEEP · 2003
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