The Cumulative Cost of Additional Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology From Chronic Sleep Restriction and Total Sleep Deprivation

Researchers: Hans P.A. Van Dongen, Ph.D.; Greg Maislin, MS, MA; Janet M. Mullington, Ph.D.; David F. Dinges, PhD

By: Michael Pouch

Summary:

Through previous research it is well established that sleep cannot be completely eliminated without having neurobehavioral consequences, thus the purpose of this study added to the debate whether human sleep can be chronically reduced without consequences. Therefore, the researchers 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.
The researcher's design method for the sleep restriction experiment included 48 participants in a chronic sleep restriction experiment or in a total sleep deprivation experiment for 14 consecutive days. Both groups were monitored for physiologically and behaviorally changes under controlled conditions and with strict schedules for the time in bed. To get a reference point for the sleep restriction group, participants had one adaptation day and two baseline days with eight-hour sleep opportunities followed by randomization to one of three sleep doses four, six, or eight hours times in bed per night, which was maintained for 14 consecutive days. This was compared to the total sleep deprivation group involved three nights straight without sleep. Each study also involved 3 baselines (pre-deprivation) days and 3 recovery days.
Results of the sleep restriction group which saw sleep periods to 4 or 6 hours per night over 14 consecutive days saw significant cumulative, dose-dependent deficits in cognitive performance on all tasks. According to the sleepiness ratings, there were acute responses to sleep restriction but only small further increases on subsequent days and did not significantly differentiate the 4 to 6 hour of sleep conditions.  In addition, there was a magnitude of changes in performance over days of sleep restriction in the 6 hours of sleep period condition was between that observed for 4 to 8 hours of sleep period conditions. Researchers also saw similarities within cognitive performance deficits between the two groups were six hours or less sleep per night is equivalent to up to two sleep deprive nights
Researchers came to conclude that six hours or less sleep per night is a good reference point to say that this range of sleep produced cognitive performance deficits equivalent to up to 2 nights of total sleep deprivation. In addition, participants were largely unaware of these increasing cognitive deficits throughout the study. In the end, the results of the study shown that adding additional wakefulness over time has neurobiological cost.

Critique
Though it is well established that sleep cannot be completely eliminated without waking neurobehavioral consequences, the researchers added their own twist to this field by studying the effects of reducing the time for sleep during the work week or for even longer periods to see if there are any consequences from this sleep cycle. I found it interesting that even relatively moderate sleep restriction can seriously impair waking neurobehavioral functions in healthy adults. The researchers did not just measure sleep debt but took it a step further by placing restrictions on sleep and seeing how this impairs individuals. In my opinion, I feel the researchers made this more realistic by adding this feature to their study. Overall, I feel this study points out different sleep cycles and restrictions have consequences on an individual cognitive performance.

Reference:
Dongen, H. P., Maislin, G., Mullington, J. M., & Dinges, D. F. (2003). The Cumulative Cost of Additional     Wakefulness: Dose-Response Effects on Neurobehavioral Functions and Sleep Physiology From     Chronic Sleep Restriction and Total Sleep Deprivation. Sleep, 26(2), 117-126.     doi:10.1093/sleep/26.2.117.
Reference found: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.693.6032&rep=rep1&type=pdf