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Sleep deprivation in humans: summary of scientific findings
Laboratory sleep deprivation studies are rare, but they do occur.
Here's a summary of what has been learned.
Behavioral changes
- No psychotic behavior (Most of the evidence of people with psychotic
behavior during sleep deprivation comes from schizophrenic patients,
people with abnormal behavior in normal life or particular situations
like a military regime). In a study of 112 hrs. of sleep deprivation,
7/350 people had symptoms resembling acute paranoid schizophrenia.
All 7 showed some predisposition towards psychotic behavior.
- Visual misperceptions are common, the extent depending on the
length of the deprivation.
(Interesting example of suggestibility; i.e. experimenters commenting
that this and this may happen ...)
- Mood changes incl. irritability, difficulty in concentrating,
disorientation and fatigue.
- Sleep-deprivation as a treatment for depression. A review of
61 papers showed that depression symptoms were ameliorated in 1003/1700
depressed patients. Serotonin
increase?
Determinants of the impact of sleep loss.
- Sleep-circadian influences.
- Prior sleep amount and distribution (like nutritional status
and fasting).
- Length of time awake.
- Circadian time.
- Situational characteristics.
- Noise.
- Exercise.
- Temperature.
- Drugs.
- Subject characteristics.
- Interest level in test/experiment.
- Motivation.
- History of exposure to sleep loss.
- Age. Interestingly, there does not seem to be any important difference
in coping with sleep loss depending on age. It must be noted that
the baseline performance in some of the tests (like reaction times)
is age-dependent. The decrease from baseline levels is what seems
not to change significantly.
- Good/poor sleepers. There was no significant difference when
comparing insomniacs and normal sleepers.
Recovery sleep
More slow wave sleep during recovery. This occurs even in babies
(who are known to have a large proportion of REM sleep).
Neurological Changes
Hand tremor, mild nystagmus, intermittent slurring of speech.
Slowing of the EEG signals even while subjects are speaking and clearly
awake.
Sleep-deprivation as epilepsy inducer.
Autonomic changes
No changes in blood pressure, heart rate, respiration rate, skin
conductance.
Thermoregulation: No clear indication of deterioration.
Some studies claim there is a 0.3C decrease in temperature. There
is a clear circadian rhythmicity (as in non-deprived subjects).
But: We do not know about the longer-term deprivation (and
actually, in rats, temperature effects were not noted until after
a week of deprivation).
An 84-hr. deprivation study reported no change in overall body metabolism
in animals.
No changes in body weight. Subjects do tend to eat more during the
first days of deprivation.
Biochemical changes
- No changes in cortisol, epinephrine, hematocrit, plasma glucose.
- No change in adrenal or sex hormones.
- Increase in melatonin.
There may be changes in the immune system, but this remains controversial.
A
2007 study showed some effect on sleep deprivation on the immune system.
Related: Polyphasic sleep
Microsleep
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