The cumulative cost of additional wakefulness: dose-response effects on neurobehavioral functions and sleep physiology from chronic sleep restriction and total sleep deprivation.
Level 2 - randomized trial
Randomized controlled laboratory trial in healthy humans.
PubMed 12683469 · doi:10.1093/sleep/26.2.117
What was done
Forty-eight healthy adults aged 21–38 were monitored continuously in a laboratory setting across 3 baseline days, an intervention phase, and 3 recovery days. Participants were randomized to chronic sleep restriction of 4 h, 6 h, or 8 h time in bed per night for 14 consecutive nights, or to a total sleep deprivation protocol (0 h time in bed for 3 nights). Outcomes included waking cognitive performance across multiple tasks, subjective sleepiness ratings, polysomnography, and non-REM sleep EEG delta power.
What was found
Sleep restriction to 4 h or 6 h per night for 14 days caused cumulative, dose-dependent deficits on all cognitive tasks, matching performance impairments seen after up to 2 nights of total sleep deprivation. Subjective sleepiness increased acutely but changed little on subsequent days, failing to significantly differentiate the 4 h and 6 h groups. Non-REM delta power and polysomnographic variables also showed an acute initial shift with negligible subsequent changes across the 14 days. Behavioral alertness lapses were near-linearly related to cumulative wakefulness exceeding 15.84 h (s.e. 0.73 h).
Why it matters
Moderate chronic sleep restriction (6 hours or less nightly) causes substantial, accumulating neurobehavioral impairment. Because subjective perception of sleepiness rapidly plateaus, individuals cannot accurately gauge their own growing cognitive deficits.
Limits
The sample size was modest (n = 48 split across four experimental arms). The study evaluated only healthy young adults in an artificial laboratory environment, limiting direct generalization to older populations, clinical cohorts, or free-living conditions. Exact numerical performance scores for individual cognitive tasks were not reported in the abstract.
Cited by
- supports At an average of six hours of sleep per night, people begin to show measurable problems on average.