OR WILL YOU?
Let's look at a couple of studies testing this:
Acute Versus Chronic Partial Sleep Deprivation in Middle-Aged People:Differential Effect on Performance and Sleepiness (Philip et al, Sleep. Jul 1, 2012; 35(7): 997–1002.)
18 healthy men aged 46-55years underwent: Habitual night followed by either:
OK, so what did they find :
1. Number of lapses was higher after acute sleep deprivation (Left panel) or two or more nights of chronic sleep restriction (Right panel) than after the baseline night (B), but returned to the baseline after the recovery night (Ra and Rc, respectively)
2. Time taken to fall asleep was ABNORMALLY shorter after acute sleep deprivation (Left panel) or one or more nights of chronic sleep restriction (Right panel) than after the
baseline night (B), but returned to the baseline
after the recovery night (Ra and Rc, respectively)
3. People reported being MUCH MORE SLEEPY after acute sleep deprivation (Left panel) or one or after chronic sleep restriction (Right panel) than after the baseline night (B), but returned to the baseline after the recovery night (Ra and Rc, respectively). Sleepiness was much higher with one night of total sleep deprivation than with 1-5 nights of chronically reduced sleep (the so called 'HABITUATION EFFECT').
While chronically sleep restrivcted people did not REPORT being that sleepy, their MSLT showed that they were in fact, very sleepy. This may suggest that chronically sleep deprived people underestimate their sleepiness.
=========================================================================
Another study by Van Dongen et al looked at 14 days of sleep restriction. Here is the abstract:
Subjective sleepiness ratings showed an acute response to sleep restriction but only small further increases on subsequent days, and did not significantly differentiate the 6 h and 4 h conditions.
Polysomnographic variables and delta power in the non-REM sleep EEG-a putative marker of sleep homeostasis--displayed an acute response to sleep restriction with negligible further changes across the 14 restricted nights.
Comparison of chronic sleep restriction to total sleep deprivation showed that the latter resulted in disproportionately large waking neurobehavioral and sleep delta power responses relative to how much sleep was lost.
A statistical model revealed that, regardless of the mode of sleep deprivation, lapses in behavioral alertness were near-linearly related to the cumulative duration of wakefulness in excess of 15.84 h (s.e. 0.73 h).
Sleepiness ratings suggest that subjects were largely unaware of these increasing cognitive deficits, which may explain why the impact of chronic sleep restriction on waking cognitive functions is often assumed to be benign.
Physiological sleep responses to chronic restriction did not mirror waking neurobehavioral responses, but cumulative wakefulness in excess of a 15.84 h predicted performance lapses across all four experimental conditions. This suggests that sleep debt is perhaps best understood as resulting in additional wakefulness that has a neurobiological "cost" which accumulates over time.
Neurobehavioral responses to varying doses of daily sleep. Four different neurobehavioral assays served to measure cognitive performance capability and subjective sleepiness.
Each panel displays group averages for subjects in the 8 h (diamonds), 6 h (open squared), and 4 h (circles) chronic sleep period conditions across 14 days, and in the 0 h (solid squares) sleep condition across 3 days.
Subjects were tested every 2 h each day; data points represent the daily average (07:30–23:30) expressed relative to baseline (BL).
Panel A shows psychomotor vigilance task (PVT) performance lapses;
panel B shows Stanford Sleepiness Scale (SSS) self-ratings;
panel C shows digit symbol substitution task (DSST) correct responses;
panel D shows serial addition/subtraction task (SAST) correct responses per min.
Upward corresponds to worse performance on the PVT and greater sleepiness on the SSS, and to better performance on the DSST and the SAST. The curves through the data points represent statistical non-linear model-based best-fitting profiles of the response to sleep deprivation (equation (1)) for subjects in each of the four experimental conditions.
The mean ± s.e. ranges of neurobehavioral functions for 1 and 2 days of 0 h sleep (total
sleep deprivation) are shown as light and dark gray bands, respectively, allowing comparison of the 3-day total sleep deprivation condition and the 14-day chronic sleep restriction conditions. For the DSST and SAST, these gray bands are curved parallel to the practice effect displayed by the subjects in the 8 h sleep period condition, to compensate for different amounts of practice on these tasks.
- 1 night of total sleep loss (acute sleep deprivation, SD) followed by an 8-hr recovery night (Ra) OR
- 5 consecutive nights of sleep restriction with of 4 hrs of sleep every night (SR1, SR2, SR3. SR4), or chronic sleep followed by an 8-hr recovery night (Rc).
- Multiple sleep latency test: The MSLT is a full-day test that consists of five scheduled naps separated by two-hour breaks. During each nap trial, you will lie quietly in bed and try to go to sleep. Once the lights go off, the test will measure how long it takes for you to fall asleep. You will be awakened after sleeping 15 minutes. If you do not fall asleep within 20 minutes, the nap trial will end.What is being evaluated is how much time does it take for you to fall asleep during the naps on an average. Anything below 5 minutes is considered very sleepy.
- Karolinska Sleepiness Scale scores: People rate their sleepiness on this 9-point scale, from 1 = “extremely alert” to 9 = “very sleepy, great effort to keep alert, fighting sleep.”
- simple reaction time test: A black square was displayed 100 times on the screen at randomized (2–7 s) intervals over 10 min. The participant was required to respond to the stimulus by pressing a key to turn off the square.The number of times people missed it (lapses) was counted. The sleepier/ more inattentive you are, the more lapses you could be expected to have.
OK, so what did they find :
1. Number of lapses was higher after acute sleep deprivation (Left panel) or two or more nights of chronic sleep restriction (Right panel) than after the baseline night (B), but returned to the baseline after the recovery night (Ra and Rc, respectively)
3. People reported being MUCH MORE SLEEPY after acute sleep deprivation (Left panel) or one or after chronic sleep restriction (Right panel) than after the baseline night (B), but returned to the baseline after the recovery night (Ra and Rc, respectively). Sleepiness was much higher with one night of total sleep deprivation than with 1-5 nights of chronically reduced sleep (the so called 'HABITUATION EFFECT').
While chronically sleep restrivcted people did not REPORT being that sleepy, their MSLT showed that they were in fact, very sleepy. This may suggest that chronically sleep deprived people underestimate their sleepiness.
=========================================================================
Another study by Van Dongen et al looked at 14 days of sleep restriction. Here is the abstract:
OBJECTIVES:
To inform the debate over whether human sleep can be chronically reduced without consequences, we conducted a dose-response chronic sleep restriction experiment in which waking neurobehavioral and sleep physiological functions were monitored and compared to those for total sleep deprivation.DESIGN:
The chronic sleep restriction experiment involved randomization to one of three sleep doses (4 h, 6 h, or 8 h time in bed per night), which were maintained for 14 consecutive days. The total sleep deprivation experiment involved 3 nights without sleep (0 h time in bed). Each study also involved 3 baseline (pre-deprivation) days and 3 recovery days.SETTING:
Both experiments were conducted under standardized laboratory conditions with continuous behavioral, physiological and medical monitoring.PARTICIPANTS:
A total of n = 48 healthy adults (ages 21-38) participated in the experiments.INTERVENTIONS:
Noctumal sleep periods were restricted to 8 h, 6 h or 4 h per day for 14 days, or to 0 h for 3 days. All other sleep was prohibited.RESULTS:
Chronic restriction of sleep periods to 4 h or 6 h per night over 14 consecutive days resulted in significant cumulative, dose-dependent deficits in cognitive performance on all tasks.Subjective sleepiness ratings showed an acute response to sleep restriction but only small further increases on subsequent days, and did not significantly differentiate the 6 h and 4 h conditions.
Polysomnographic variables and delta power in the non-REM sleep EEG-a putative marker of sleep homeostasis--displayed an acute response to sleep restriction with negligible further changes across the 14 restricted nights.
Comparison of chronic sleep restriction to total sleep deprivation showed that the latter resulted in disproportionately large waking neurobehavioral and sleep delta power responses relative to how much sleep was lost.
A statistical model revealed that, regardless of the mode of sleep deprivation, lapses in behavioral alertness were near-linearly related to the cumulative duration of wakefulness in excess of 15.84 h (s.e. 0.73 h).
CONCLUSIONS:
Since 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, it appears that even relatively moderate sleep restriction can seriously impair waking neurobehavioral functions in healthy adults.Sleepiness ratings suggest that subjects were largely unaware of these increasing cognitive deficits, which may explain why the impact of chronic sleep restriction on waking cognitive functions is often assumed to be benign.
Physiological sleep responses to chronic restriction did not mirror waking neurobehavioral responses, but cumulative wakefulness in excess of a 15.84 h predicted performance lapses across all four experimental conditions. This suggests that sleep debt is perhaps best understood as resulting in additional wakefulness that has a neurobiological "cost" which accumulates over time.
Neurobehavioral responses to varying doses of daily sleep. Four different neurobehavioral assays served to measure cognitive performance capability and subjective sleepiness.
Each panel displays group averages for subjects in the 8 h (diamonds), 6 h (open squared), and 4 h (circles) chronic sleep period conditions across 14 days, and in the 0 h (solid squares) sleep condition across 3 days.
Subjects were tested every 2 h each day; data points represent the daily average (07:30–23:30) expressed relative to baseline (BL).
Panel A shows psychomotor vigilance task (PVT) performance lapses;
panel B shows Stanford Sleepiness Scale (SSS) self-ratings;
panel C shows digit symbol substitution task (DSST) correct responses;
panel D shows serial addition/subtraction task (SAST) correct responses per min.
Upward corresponds to worse performance on the PVT and greater sleepiness on the SSS, and to better performance on the DSST and the SAST. The curves through the data points represent statistical non-linear model-based best-fitting profiles of the response to sleep deprivation (equation (1)) for subjects in each of the four experimental conditions.
The mean ± s.e. ranges of neurobehavioral functions for 1 and 2 days of 0 h sleep (total
sleep deprivation) are shown as light and dark gray bands, respectively, allowing comparison of the 3-day total sleep deprivation condition and the 14-day chronic sleep restriction conditions. For the DSST and SAST, these gray bands are curved parallel to the practice effect displayed by the subjects in the 8 h sleep period condition, to compensate for different amounts of practice on these tasks.
No comments:
Post a Comment