Sleep debt
Encyclopedia
Sleep
Sleep is a naturally recurring state characterized by reduced or absent consciousness, relatively suspended sensory activity, and inactivity of nearly all voluntary muscles. It is distinguished from quiet wakefulness by a decreased ability to react to stimuli, and is more easily reversible than...
. A large sleep debt may lead to mental and/or physical fatigue.
There are presumed to be two kinds of sleep debt, caused by partial sleep deprivation
Sleep deprivation
Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. Few studies have compared the...
or total sleep deprivation. Partial sleep deprivation occurs when a person or a lab animal
Animal testing
Animal testing, also known as animal experimentation, animal research, and in vivo testing, is the use of non-human animals in experiments. Worldwide it is estimated that the number of vertebrate animals—from zebrafish to non-human primates—ranges from the tens of millions to more than 100 million...
sleeps too little for many days or weeks. Total sleep deprivation means being kept awake for days or weeks. There is debate in the scientific community over the specifics of sleep debt, and it is not considered to be a disorder.
Scientific debate
There is debate among researchers as to whether the concept of sleep debt describes a measurable phenomenon. The September 2004 issue of the journal Sleep contained dueling editorials from two of the world's leading sleep researchers: David F. DingesDavid F. Dinges
David F. Dinges is a major American sleep researcher and teacher.He is Professor of Psychology in Psychiatry, Chief of the Division of Sleep and Chronobiology in the Department of Psychiatry, and Associate Director of the Center for Sleep and Respiratory Neurobiology in the University of...
and Jim Horne.
A 1997 experiment conducted by psychiatrists at the University of Pennsylvania School of Medicine suggested that cumulative nocturnal sleep debt affects daytime sleepiness, particularly on the first, second, sixth, and seventh days of sleep restriction.
In one study, subjects were tested using the psychomotor vigilance task
Psychomotor vigilance task
The Psychomotor Vigilance Task is a sustained-attention, reaction-timed task that measures the speed with which subjects respond to a visual stimulus. Quantitative dependent variables involve omission and commission errors, reflecting fluctuations in endogenous cognitive condition...
(Von Dongen et al., 2003, as cited in Walker, 2009). Different groups of people were tested with variable sleep times for two weeks: 8 hours, 6 hours, 4 hours, and total sleep deprivation
Sleep deprivation
Sleep deprivation is the condition of not having enough sleep; it can be either chronic or acute. A chronic sleep-restricted state can cause fatigue, daytime sleepiness, clumsiness and weight loss or weight gain. It adversely affects the brain and cognitive function. Few studies have compared the...
. Each day they were tested for the number of lapses on the PVT. The results showed that as time went by, each group's performance worsened, with no sign of any stopping point. Another observation was that even just 6 hours of sleep a night was detrimental; people who slept 6 hours a night for 10 days had similar results to those who were completely sleep deprived for 1 day. This study gives further evidence of sleep debt, where the negative effects are shown to accumulate over time with less sleep.
Evaluation
Sleep debt has been tested in a number of studies, most notably by Klerman and Dijk, through the use of a sleep onset latencySleep onset latency
In sleep science, sleep onset latency is the length of time that it takes to accomplish the transition from full wakefulness to sleep, normally to the lightest of the non-REM sleep stages.-Sleep latency studies:...
test. This test attempts to measure how easily a person can fall asleep. When this test is done several times during a day, it is called a multiple sleep latency test
Multiple Sleep Latency Test
The Multiple Sleep Latency Test is a sleep disorder diagnostic tool. It is used to measure the time elapsed from the start of a daytime nap period to the first signs of sleep, called sleep latency...
(MSLT). The subject is told to go to sleep and is awakened after determining the amount of time it took to fall asleep.
The Epworth Sleepiness Scale
Epworth Sleepiness Scale
The Epworth Sleepiness Scale is a scale intended to measure daytime sleepiness that is measured by use of a very short questionnaire. This can be helpful in diagnosing sleep disorders...
(ESS) is among the tools used to screen for potential sleep debt. Specifically, the ESS, created by Australian researchers, is a simple eight item questionnaire with scores ranging from 0 to 24.
A January 2007 study from Washington University in St. Louis
Washington University in St. Louis
Washington University in St. Louis is a private research university located in suburban St. Louis, Missouri. Founded in 1853, and named for George Washington, the university has students and faculty from all fifty U.S. states and more than 110 nations...
suggests that saliva tests of the enzyme amylase
Amylase
Amylase is an enzyme that catalyses the breakdown of starch into sugars. Amylase is present in human saliva, where it begins the chemical process of digestion. Food that contains much starch but little sugar, such as rice and potato, taste slightly sweet as they are chewed because amylase turns...
could be used to indicate sleep debt, as the enzyme increases its activity in correlation with the length of time a subject has been deprived of sleep.
The control of wakefulness has recently been found to be strongly influenced by the newly discovered protein orexin
Orexin
Orexins, also called hypocretins, are the common names given to a pair of excitatory neuropeptide hormones that were simultaneously discovered by two groups of researchers in rat brains....
. A 2009 study from Washington University in St. Louis has illuminated important connections between sleep deprivation (sleep debt), orexin
Orexin
Orexins, also called hypocretins, are the common names given to a pair of excitatory neuropeptide hormones that were simultaneously discovered by two groups of researchers in rat brains....
, and amyloid beta
Amyloid beta
Amyloid beta is a peptide of 36–43 amino acids that is processed from the Amyloid precursor protein. While it is most commonly known in association with Alzheimer's disease, it does not exist specifically to cause disease...
, with the suggestion that the development of Alzheimer's disease
Alzheimer's disease
Alzheimer's disease also known in medical literature as Alzheimer disease is the most common form of dementia. There is no cure for the disease, which worsens as it progresses, and eventually leads to death...
could hypothetically be a result of chronic sleep debt or overly long periods of wakefulness.
Across society
National Geographic MagazineNational Geographic Magazine
National Geographic, formerly the National Geographic Magazine, is the official journal of the National Geographic Society. It published its first issue in 1888, just nine months after the Society itself was founded...
has reported that the demands of work, social activities, and the availability of 24-hour home entertainment and internet access have caused people to sleep less now than in premodern times. USA Today
USA Today
USA Today is a national American daily newspaper published by the Gannett Company. It was founded by Al Neuharth. The newspaper vies with The Wall Street Journal for the position of having the widest circulation of any newspaper in the United States, something it previously held since 2003...
reported in 2007 that most adults in the USA get about an hour less than the average sleep time 40 years ago.
However, Jim Horne, a sleep researcher at Loughborough University
Loughborough University
Loughborough University is a research based campus university located in the market town of Loughborough, Leicestershire, in the East Midlands of England...
, questions such claims. In a 2004 editorial in the journal Sleep, he notes available data suggest the average number of hours of sleep in a 24-hour period has not changed significantly in recent decades among adults. Furthermore, the editorial suggests that there is a range of normal sleep time required by healthy adults, and many indicators used to suggest chronic sleepiness among the population as a whole do not stand up to scientific scrutiny.
Comparing data collected from the Bureau of Labor Statistics
Bureau of Labor Statistics
The Bureau of Labor Statistics is a unit of the United States Department of Labor. It is the principal fact-finding agency for the U.S. government in the broad field of labor economics and statistics. The BLS is a governmental statistical agency that collects, processes, analyzes, and...
' American Time Use Survey from 1965–1985 and 1998–2001 shows that the median amount of sleep, napping, and resting done by the average adult American has changed by less than 0.7%, from a median of 482 minutes per day from 1965 through 1985, to 479 minutes per day from 1998 through 2001.
External links
- Harvard Magazine article, "Deep into Sleep"
- Lost Sleep Can't Be Made Up, Study Suggests – LiveScienceLiveScienceLiveScience is a science news website run by TechMediaNetwork, who purchased it from Imaginova in 2009. Stories and editorial commentary are commonly syndicated to major news outlets, such as Yahoo!, MSNBC, AOL, and Fox News....
Further reading
- Dement, William C., MD, PhD "The Promise of Sleep.", Delacorte Press, Random House Inc., New York, 1999.