Sleep restriction studies

Chronic partial sleep restriction is a topic of current interest and one that was examined two decades ago by Carskadon and Dement (18). During a week of restriction to 5 hr of sleep a night, 10 college-aged adults manifested an accumulating decrease of sleep latency scores that did not plateau. A more recent chronic sleep restriction study (34) showed a. 95 correlation of performance measures with the Carskadon and Dement MSLT scores. These studies provided important support for the concept of sleep deficits that continue to grow as sleep reduction is prolonged. A more recent interpretation implicates excess wake as the primary factor rather than sleep deficit (35). 

Results from other variables assessed in sleep restriction studies are less consistent. For example, some studies have found no deficits in tasks assessing motor skills (48,49), auditory attention (47,48), sustained attention and response inhibition (50), memory tasks (47,49,139), and computational accuracy... 

Moreover, daily PVT lapse rates increased at a more rapid rate in the reduced sleep conditions. Figure 4 displays the results from the first of these studies, in which subjects were restricted to 4, 6, or 8-hr time in bed for sleep for 14 consecutive days (35). The results were compared to 88 hr of total sleep deprivation. Figure 4 illustrates the dose-response relationship between sleep opportunity and the degree of impairment in PVT performance. Interestingly, this cumulative impairment was found to be almost linear for lapse rates. Further, subjects randomized to the 4- and 6-hr sleep restriction conditions reached levels of impairment equivalent to those of subjects undergoing 1-2 nights of total sleep deprivation. 

Belenky G, Wesensten NJ, Thorne DR, Thomas ML, Sing HC, Redmond DP, Russo MB, Balkin TJ. Patterns of performance degradation and restoration during sleep restriction and subsequent recovery a sleep-dose response study. J Sleep Res 2003 12 1-12. 

The effect of sleep loss associated with medical disorders can manifest in several ways. Several studies have reported on the detrimental effects of sleep restriction on neurobehavioral functioning. Following only one night of restricted sleep decreased neurobehavioral performance and increased subjective sleepiness and sleep propensity have been reported (1). When the number of nights of sleep restriction is extended beyond one, cumulative decrements in neurobehavioral functioning (2,3) and increased daytime sleepiness levels are evident (4). 

We are using the term inadequate sleep instead of sleep deprivation in our title for a number of reasons. First, few studies have aimed specifically to deprive children or adolescents of sleep. We describe some research on experimental sleep restriction in children but most of these studies fall far short of common deprivation paradigms in animals or even adult humans. Instead, most research in younger humans has assessed outcome measures such as school grades, self-reported sleepiness, and so forth as a function of variations in self-selected or usual sleep patterns with the expectation that children and adolescents who obtain lower than normal amounts of sleep will manifest deficits. Thus, inadequate sleep is defined by sleep characteristics of a sample. We also wanted to note some of the literature on sleep that is disturbed or disrupted due to disease processes such as apnea or periodic leg movements the duration of sleep in sleep disorders may or may not be shortened or restricted although it is likely fragmented and otherwise abnormal. We decided on the term inadequate sleep with the hope that it would encompass these different areas of concern. 

VI. Experimental Studies of Sleep Restriction/Disruption and Circadian Timing... 

The results from the studies described above indicate that the MSLT provides a robust measure of sleepiness that is sensitive to sleep restriction in children and adolescents (112). Patterns of sleep latency from repeated naps during constant routine protocols or forced desynchrony protocols in older children and adolescents also illustrate the influences of both homeostatic and circadian processes on sleepiness/alertness and provide evidence for the hypothesis that... 

Clearly, more experimental research is needed to tease apart the developmental influences of sleep restriction and/or disruption on a range of daytime functioning behaviors and cognitive skills. Additionally, studies are needed that restrict sleep for extended periods of time to identify deficits that may be associated with the typical sleep patterns of children and adolescents. 

A creative series of studies found that young adult volunteers could reduce their habitual sleep from 8 hr to about 5 hr with almost undetectable effects on performance or mood, except for an increase in sleepiness (42,43). Such investigations should be repeated and expanded, to see if such sleep restriction is so free of morbid risk. 

Until recently, it has been assumed that the performance effects of chronic sleep restriction were a milder version of the effects of acute, total sleep deprivation and that recovery from both was rapid once normal amounts of sleep were restored. Results from a study recently completed in our laboratory suggest that this may not be the case. 

In a sleep dose-response study (3,8) we examined the effects of three conditions of sleep restriction [3, 5, or 7 hr time in bed (TIB)] and one condition of sleep augmentation (9 hr TIB) on performance over 7 days and during the subsequent 3 days of recovery (all groups = 8 hr TIB). These sleep dose-response effects were compared against the training/baseline period in which all groups were allowed 8 hr TIB. 

A later study supported the findings that methylphenidate s benefits are most apparent in sleep-deprived/sleep-restricted volunteers. Roehrs et al. (52) compared the effects of 09 00 doses of 10 mg methylphenidate to placebo on sleepiness (Multiple Sleep Latency Test, MSLT), Profile of Mood States (POMS) ratings, and divided-attention performance after either 4 or 8 hr of sleep. After these test days, the 4- and 8-hr sleep conditions were repeated, but this time subjects were given their choice of drug or placebo. Results indicated that performance was improved by methylphenidate, most notably after the 4-hr condition. Methylphenidate also improved sleep latency and mood, but only after restricted sleep. During the choice phase of the study, subjects showed a preference for methylphenidate after 4 hr sleep (in 88% of opportunities), but not after 8 hr sleep (in only 29% of opportunities), suggesting that the preference for methylphenidate depended on the perceived sleepiness level of the individual. 

Friedman L, Bliwise DL, Yesavage JA, Salom SR. A preliminary study comparing sleep restriction and relaxation treatments for insomnia in older adults. J Gerontol 1991 46 Pl-8. 

Glovinsky PB, Spielman AJ. Sleep restriction therapy. In Hauri PJ, ed. Case Studies in Insomnia. New York Plenum Press, 1988. 

Some clinicians believe that sleep restriction is an effective form of treatment for chronic insomnia. Evidence from studies varies, and use of sleep restriction in many studies was part of combination therapy, and the specific contribution of sleep restriction toward sleep improvement was unclear. 

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