Consequences of sleep deprivation.

IJOMEH 2010;23(1) 95
R E V I E W P A P E R S
International Journal of Occupational Medicine and Environmental Health 2010;23(1):95 – 114
DOI 10.2478/v10001-010-0004-9
CONSEQUENCES OF SLEEP DEPRIVATION
JOLANTA ORZEŁ-GRYGLEWSKA
University of Gdańsk, Gdańsk, Poland
Department of Animal Physiology
Abstract
This paper presents the history of research and the results of recent studies on the effects of sleep deprivation in animals
and humans. Humans can bear several days of continuous sleeplessness, experiencing deterioration in wellbeing and effec-
tiveness; however, also a shorter reduction in the sleep time may lead to deteriorated functioning. Sleeplessness accounts
for impaired perception, difficulties in keeping concentration, vision disturbances, slower reactions, as well as the appear-
ance of microepisodes of sleep during wakefulness which lead to lower capabilities and efficiency of task performance and
to increased number of errors. Sleep deprivation results in poor memorizing, schematic thinking, which yields wrong deci-
sions, and emotional disturbances such as deteriorated interpersonal responses and increased aggressiveness. The symp-
toms are accompanied by brain tissue hypometabolism, particularly in the thalamus, prefrontal, frontal and occipital cortex
and motor speech centres. Sleep deficiency intensifies muscle tonus and coexisting tremor, speech performance becomes
monotonous and unclear, and sensitivity to pain is higher. Sleeplessness also relates to the changes in the immune response
and the pattern of hormonal secretion, of the growth hormone in particular. The risk of obesity, diabetes and cardiovascular
disease increases. The impairment of performance which is caused by 20–25 hours of sleeplessness is comparable to that
after ethanol intoxication at the level of 0.10% blood alcohol concentration. The consequences of chronic sleep reduction
or a shallow sleep repeated for several days tend to accumulate and resemble the effects of acute sleep deprivation lasting
several dozen hours. At work, such effects hinder proper performance of many essential tasks and in extreme situations
(machine operation or vehicle driving), sleep loss may be hazardous to the worker and his/her environment.
Key words:
Sleep deprivation, Slow-wave sleep, REM sleep, Sleeplessness, Deterioration of effectiveness, Impairment of performance
Received: July 9, 2009. Accepted: August 25, 2009.
Address reprint requests to J. Orzeł-Gryglewska, Department of Animal Physiology, University of Gdańsk, Kładki 24, 80-822 Gdańsk, Poland
(e-mail: jola@biotech.ug.gda.pl).
INTRODUCTION
Sleep deprivation consists either in a complete lack of
sleep during a certain period of time or a shorter-than-
optimal sleep time. The most common causes of sleep de-
privation are those related to contemporary lifestyle and
work-related factors; thus the condition affects a consider-
able number of people. A chronic reduction in the sleep
time or the fragmentation of sleep, leading to the disrup-
tion of the sleep cycle [1], may have consequences compa-
rable to those of severe acute sleep deprivation; this refer-
ring particularly to the cognitive functions, attention and
operant memory [2–4]. The changes in sleep time across
the circadian pattern [5], such as during shift work [6–9]
or air travel (jet-lag syndrome resulting from changing
time zones) [10], prove to be unfavourable as well. Many
people also experience mild discomfort while adjusting to
the daylight saving time. Sleep deprivation lasting as long
as several days usually takes place in extreme situations or
under experimental conditions. Sleep deficiency (insom-
nia) accompanies certain pathological states and may re-
quire treatment. Several types of sleep deprivation can be
distinguished, as shown in Table 1.
Chronic sleep deprivation in humans
The first attempts at assessing the effects of long-term
sleep deprivation date back to 1896. Three American
volunteers were subjected to a 90-hour sleep deprivation
during which one person experienced hallucinations [11],
but it was not until the 1960s that organized series of tri-
als were performed on humans [12,13], yielding sleep de-
privation of one week. This type of studies makes it pos-
sible to evaluate the influence of progressive sleep loss

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IJOMEH 2010;23(1)96
sound, and low motivation or little interest on the part of
the participants [1]. The longest period of sleep depriva-
tion achieved in a human volunteer study lasted 205 hours
(8.5 days) [12,13]. During this period, alpha waves were
absent in EEG recording, and during the waking state,
the EEG signal resembled the 1 NREM stage. Since
no method is available to keep the participants further
awake, longer periods of sleep deprivation have not been
yielded. A well-documented case of a long period of sleep
deprivation is a 17-year-old male from California who
endured 264 hours without sleep [15]. He withstood the
deprivation exceptionally well, which gave rise to a prema-
ture conclusion that long deprivation is relatively harmless
to human health. A subsequent world record for the sleep
deprivation was reported in May 2007; this time being
claimed by a 42-year-old Englishman from Cornwall [16].
on human wellbeing and behaviour. The characteristics
of consecutive nights of forced wakefulness [14] are pre-
sented in Table 2.
Generally, the clinical symptoms of sleep deprivation in-
clude longer reaction time, distractedness, disturbances in
attention and concentration, forgetting known facts, dif-
ficulty in memorizing new information, and making mis-
takes and omissions. A higher level of stress is observed;
tiredness, drowsiness and irritability increases; work ef-
fectiveness decreases and motivation usually falls down.
Reasoning slows down not only during the night of sleep
deprivation but also on the following day. Work effective-
ness decreases, particularly at the low points of the cir-
cadian rhythm and when the subjects perform long, dif-
ficult, compulsory, monotonous, sitting activities in an un-
changing environment with limited lighting, little supply of
Table 1. Types of sleep deprivation and the causes of insomnia [1–10]
Types of sleep reduction Causes Comments/examples
Commonly observed
reduction in sleep time
Daily sleep time reduction below the
level of optimal individual needs
Sleep time reduction is a common phenomenon resulting
from contemporary lifestyle
Single omission of night sleep
(24-h wakefulness)
Being on duty at work, taking care of an ill person, partying
Shifting sleep period in relation to
the circadian pattern (shift work)
In shift work, the sleep time is not concordant with the
biological rhythms and is usually shorter than that of the
natural sleep. In air travel, rapidly changing the time zones
results in the jet-lag syndrome
Considerable reduction
in sleep time
Wakefulness prolonged to several days Experimental conditions, extreme situations (e.g. tortures),
tribal shamanic rites
Selective deprivation (only REM
or 4-NREM sleep)
Experimental conditions, with polysomnographic
assessment of the sleep stages and phases
Total sleep deprivation (extreme
prolongation of wakefulness)
Only in experimental animals; the rats die after 16–21 days
of sleep loss on average, other species show lesser
disruption in functioning after a comparable sleep loss
Sleep reduction (insomnia)
due to pathological
processes
Depression, anxiety disorders In these disorders, the shallow sleep is delayed and
shortened, not providing enough rest
Addiction (medications, alcohol) Insomnia is one of the symptoms of physical addiction;
paradoxically, continuous intake of sleep-inducing
medications makes the sleep pill-dependent; alcohol
suppresses the REM sleep
Somatic, mainly painful diseases Restless leg syndrome, sleep-related breathing disorders
and certain metabolic diseases (thyroid hyperactivity)
Primary sleep disorders: idiopathic,
psychophysiological and subjective
insomnia
The causes: genetic determinants intensified by old age
and improper sleep hygiene; chronic stress, traumatic
experience, difficult life situations; inadequate subjective
assessment of the duration and quality of one’s sleep

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IJOMEH 2010;23(1) 97
need for sleep changes with age and to a certain extent de-
pends on gender and chronotype [17]. This demand varies
across individuals, as some people need only 3–5 hours of
sleep, whereas others need at least 8 hours of sleep per
night to maintain work effectiveness. Hence, the term ‘de-
privation’ applies only to the cases when impaired func-
tioning due to sleep loss can be observed. The extent to
which one experiences the effects of sleep deprivation de-
pends on individual needs. Most people declare that they
need approximately 8 hours of sleep. Nonetheless, during
a six-year questionnaire study involving over one million
participants of both genders, the lowest mortality was re-
corded in a group sleeping 6.5–7.5 hours on average [18],
which may be attributed to various reasons. Shortened
sleep (but also the one that lasts too long) correlates with
a probability of developing diabetes [19] and high blood
pressure [20]. Notably, however, a higher risk of these dis-
eases is attributed to sleep deficiency. The sleep apnoea
deteriorates the quality of sleep and thus contributes to
an increase in the sleep time needed. Moreover, such
The trial was performed despite the fact that this category
had been excluded from the Guinness Book of Records.
The result did not differ much from the Californian record
(2 hours more), probably constituting the upper limit of
human capabilities to withstand sleep deprivation.
The duration and limit of sleep time
Sleep readiness (sleep latency, recorded every two hours
from morning to evening) increases after a sleepless night
and decreases after a sleep period longer than the daily
norm. The tolerated minimum sleep time is approximate-
ly 6 hours, although for some individuals, maintaining
such sleep time over several days may result in a lower ef-
fectiveness of work performance. However, if this sleep
time regime is kept for several weeks, no deterioration
in the neurobehavioral function, apart from drowsiness,
can be seen, which can be regarded as an adaptation to
reduced sleep. Interestingly, prolonging the sleep time
by 2–3 hours over what is an individual daily norm, does
not significantly enhance one’s general efficiency. The
Table 2. Symptoms observed during consecutive nights of sleep deprivation in humans [14]
Duration of sleep
deprivation
Symptoms
Night 1. Most people are capable of withstanding one-night sleep deprivation, although a slight discomfort may be
experienced. 24-h sleeplessness does not alter behaviour; however, tremor and increased tonus, leading to
impairment in precise movements, can be observed.
Night 2. A feeling of fatigue and a stronger need for sleep is persistent, especially between 3 a.m. and 5 a.m.,
when the body temperature reaches its lowest value.
Night 3. Performing tasks that require concentration and calculating may be impaired, particularly if the tasks are dull
and repetitious. The volunteers become irritated and impolite in any instance of disagreement. During early-
morning hours, the subjects experience an overpowering need for sleep. Remaining wakeful is possible only
with the help of the observers who wake the volunteers up if necessary.
Night 4. Prolonged microepisodes of sleep occur: the subjects discontinue their activities and stare into space; the
delta waves are recorded in the EEG output signal, even if the person is awake. Sleep microepisodes impair
performance of the tasks that require attention over a period of time. Subjects may also experience perception
disorders, illusions, hallucinations, irritation, inaccuracy and the ‘hat phenomenon’ (a feeling of pressure
around the head).
Night 5. The symptoms become more intense and include disturbances in reasoning and orientation, visual and tactile
hallucinations, fatigue, irritability and delusions. The subjects may exhibit distrust: suspecting that someone
attempts to murder them is a characteristic syndrome at this stage. Intellectual and problem-solving abilities are
considerably impaired.
Night 6. Participants develop symptoms of depersonalization and they are no longer capable of interpreting reality.
This syndrome is known as the sleep deprivation psychosis (very rarely persisting after the termination of the
experiment; it usually subsides after a sufficient time of sleeping).

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findings did not reveal any cause of death [28–30]. The
animals which survived acute deprivation (that were
eventually allowed to sleep) showed a dramatic compen-
satory increase in the REM sleep [31]. The other symp-
toms subsided within 24 hours, which indicates that the
sleep deprivation did not exert destructive effects either
on the cells, the neurons or the vital organs. Nonetheless,
a complete recovery of the pre-deprivation levels of the
particular sleep stages, or of the heart rate and body tem-
perature, lasted several days [32,33].
An interesting exception to the rule can be observed
among marine mammals: despite the periodic, significant
sleep restriction, they do not experience the recovery sleep
that would be a typical reaction to prolonged wakefulness,
as well as to 4 NREM or REM sleep deficiency, in terres-
trial mammals. The seals, for example, when staying in the
ocean, can function well for several weeks despite the fact
that they exhibit a considerably low duration of the REM
sleep. Their sleep architecture changes immediately after
they come back to the land. Unihemispheric slow-wave
sleep (characteristic of dolphins and whales) is replaced by
alternate NREM and REM phases. The sleep time typical
for terrestrial conditions is immediately restored, and no
symptoms of developing the recovery sleep can be seen [34].
Similarly, no rebound sleep occurs in infant dolphins and
their mothers who refrain from sleeping throughout the
period from the delivery till the youngsters achieve some
self-sufficiency, which can last several weeks [35]. The
ability to withstand sleep deprivation is dependent on the
species-related natural sleep characteristics regarding the
duration and quality of sleep. For instance, large ungulate
herbivores have a short, shallow and intermittent sleep,
while predators usually sleep long and deeply.
The relationship between sleep deprivation and the level
of stress has not been fully explained, although the lat-
ter may have a varying influence on the compensation
for sleep deficits. In a study reporting on wakefulness
maintained through immobilization for 0.5 to 4 hours,
the recovery sleep became significantly shorter when the
immobilization period reached its maximal duration [36].
Two-hour immobilization repeated on the consecutive
days of the experiment produced similar effects. However,
conditions as depression (both in the shorter or prolonged
sleep), heart diseases, poor general health, or even the be-
ginning of lethal processes preceding death, do prolong
the sleep time, and at the same time, they may constitute
a cause of higher mortality. The psychological profile of
the short and long sleepers is also interesting: at the op-
posite ends of the U-shaped curve showing the death rate
variability in relation to sleep time, there are ambitious,
active, energetic workaholics, for whom sleep means
a waste of time, and the sorrowful, depressive introverts
who seek escape from life hardships into sleep. However,
a possibility that the sleep duration itself may have influ-
ence on the capacity to survive cannot be excluded [18].
Total sleep deprivation in animals
The first report on the total chronic sleep deprivation in
rats dates back to 1962 [21]. The animals were kept awake
for 27 days, which led to aggressive behaviour, decreased
body mass gain and impairment of the startle response.
The most detailed analysis of sleep deprivation was based
on data deriving from well designed, several-year ex-
periments conducted by Bergmann and Rechtschaffen
[22–26]. The experiments were performed using the disk-
over-water method, with a rat being placed on a disk over
a layer of water, and a polysomnograph signal setting the
disk into motion whenever an initiation of sleep was re-
corded [27]. The sleep deprivation obtained using this
procedure made up 70–90% of the experiment time and
led to the death of the animals within 2–3 weeks. In the
course of the experiment, weight loss was observed de-
spite an increased food intake, as well as pathological skin
reactions on the tail and paws and a bad condition of the
fur. Initially, body temperature was elevated, but it de-
creased during the period preceding death. Plasma levels
of the thyroid hormones decreased significantly and heart
rate increased. At the same time, no stress symptoms, such
as stomach ulcers, elevated ACTH or corticosterone lev-
els, or decreased metabolic rate, could be observed dur-
ing the experiment [26,27]. Rats died within 11–32 days
(16–21 days on average) from the onset of deprivation,
a period comparable to that of food deprivation with
lethal effects (17–19 days). However, histopathological

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IJOMEH 2010;23(1) 99
sleep, the proportion of REM sleep increases (above 50%),
mainly due to an increased number of REM episodes [36].
The compensatory period may last several days and is pro-
portional to the period of deprivation. Selective 4 NREM
stage deprivation also leads to an increase in the percent-
age rate of this stage during the post-deprivation period.
However, it is difficult to enforce a complete deprivation
of the deep sleep since the number of delta waves tends to
increase during the remaining sleep stages. Sleep disrup-
tion results in a greater need for PS sleep. The polysomno-
graphic recording of PS shows slow-wave episodes (lasting
several dozen seconds) with atony and hippocampal theta
rhythm [48]. The subjects show a depressive effect reflect-
ed by decreased reactivity.
ThE cONSEquENcES Of SLEEp LOSS
OR SLEEp RESTRIcTION
Tonus, posture maintenance and physical
exercise capacity
An increase in muscle tonus compensates for the decreased
attention during sleep deprivation and makes it possible to
maintain the initial level of the test results [49]. Evidence
for this finding comes from the observations concerning
tired individuals who, when tested at late hours, showed an
increased facial muscle tonus [50]. Higher muscle tonus is
accompanied by tremor whose amplitude usually increas-
es under conditions of fatigue [51,52]. Twenty-four hours
of sleep deprivation led to the disturbances in postural
control which intensified with the duration of sleepless-
ness [53]. A possible explanation may be the changes in
the sensory integration that may be concurrent with the
visual deficiencies caused by sleep deprivation [54]. Dur-
ing the sleep deprivation, stimulating the muscles involved
in postural control with a 205-second vibration stimulus
resulted in a false perception of movement and deteriora-
tion in maintaining body balance. Interestingly, the most
significant balance disorders occurred after 100–150 sec-
onds of stimulation, which is a period sufficient to develop
adaptation to such uncommon proprioceptive stimuli.
The disruption was augmented after closing the eyes [55].
Assuming a standing posture instead of the sitting one
a single 2-hour immobilization resulted in an 92% in-
crease in paradoxical sleep within the following 10 hours,
whereas a 2-hour wakefulness, maintained using standard
methods (disk or gentle handling), did not significantly af-
fect the sleep that followed [37].
Rats appear to be particularly vulnerable to sleep depriva-
tion enforced using the moving disk method, since in other
animals (pigeons), the changes observed after 24–29 days
of this procedure were not as severe as in rats [38]. Other
deprivation procedures were not lethal either to rats or
other laboratory animals [39], although this may have
been due to the significantly shorter periods of deprivation
under other experimental conditions or to the difficulties
in achieving total sleep deprivation.
post-deprivation recovery: rebound sleep
Rebound sleep takes place after the sleep deprivation and
is longer than the usual sleep time. It is composed of lon-
ger periods of the delta-wave sleep and REM sleep, while
stage 2 NREM is shortened and stage 1 NREM may be
absent [31,40,41]. The duration of the rebound sleep does
not correspond to the total duration of sleep loss; the sleep
lasting several hours more than usual may provide sufficient
recovery even within the first 24 hours post-deprivation. In
rats, REM deficiencies after 24 hours of sleep deprivation
are compensated mainly during the initial period of recov-
ery, mostly within the light sleep phase, whereas the com-
pensation for NREM deficiency proceeds at a slower pace.
The post-deprivation changes in the sleep may be present
for several days [32], gradually losing their intensity.
Selective REM sleep deprivation (waking up at the begin-
ning of REM episodes) makes the entry into REM more
frequent: the longer the paradoxical sleep (PS) depriva-
tion, the higher the number of interventions necessary to
prevent this sleep phase. This finding indicates a progres-
sive increase in PS propensity [42,43]. At the same time,
selective REM sleep deprivation leads to the deterioration
of cognitive functions. Annoyance, anxiety and difficulty
in focusing attention result [44], while drowsiness during
daytime does not increase [45]. Other symptoms include
increased heart rate [33]. Apart from that, hypersexuality
has also been observed in rats [46,47]. During the rebound