How much sleep is needed to recover from sleep deprivation? Several other studies have tried to find the answer.

In a 2020 randomized trial, 1 night of total sleep deprivation followed by 2 nights of sleep recovery (12 and 8 hours) restored hippocampal connectivity but not memory performance.^[2]

A 2016 trial comparing the participants’ optimal sleep duration to their habitual sleep duration found that individuals who routinely underslept by an hour may need up to 9 days of unrestricted sleep to recover.^[3]

A 2003 trial explored the dose-response of chronic sleep deprivation. It found that even moderate sleep loss could impair neurobehavioral function.^[4]

🔍 Digging Deeper: A summary of the 2003 trial

Cognitive throughput is impaired by ≤4 hours of sleep per day. Working memory and behavioral alertness are impaired by ≤6 hours of sleep per day. These impairments kept worsening over the two weeks the trial lasted.

Study: In this randomized control trial, 48 healthy adults (aged 21–38) were divided into four groups. The three groups who underwent limited sleep for two weeks (4, 6, and 8 hours/day) were compared to a fourth group who didn’t sleep for 88 hours.

All four interventions ended with 3 days of sleep recovery. The participants underwent neurobehavioral assessments every 2 hours of wakefulness.

Results: Compared to the group who slept for 8 hours/day, the group who slept for 6 hours/day showed a progressive decrease in cognitive accuracy and speed and a progressive increase in their number of lapses in behavioral alertness over the 2 weeks of the intervention. These effects were even more pronounced in the group who slept 4 hours/day.

6 days of 4-hour sleep impaired behavioral alertness and working memory as much as 1 day of total sleep deprivation.
12 days of 4-hour sleep impaired behavioral alertness and working memory as much as 2 days of total sleep deprivation.
12–14 days of 6-hour sleep impaired behavioral alertness and working memory as much as 1 day of total sleep deprivation.

(Keep in mind that the limited-sleep interventions lasted only two weeks. Had they lasted longer, behavioral alertness and working memory may have kept declining.)

All this suggests that even moderate sleep loss can impair neurobehavioral function.

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Can a week of unrestricted sleep make up for long-term sleep loss? Original paper