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Sleep Paralysis
Last edited |
10/22/2008
Sleep Paralysis is a
transient and generalized inability to move and speak that occurs during the
transitional period between sleep and wakefulness
Episodes can vary in
duration from one to several minutes and are usually extremely distressing for
the individual, especially when accompanied by
hypnagogic or
hypnopompic hallucinations.
HISTORY
Many vivid
descriptions of Sleep Paralysis can be found in the literature of the 19th
century (in Maupassant's Le Horla and in Melville's Moby Dick, for example) and
of the early 20th.
The following excerpt is from F. Scott Fitzgerald's The Beautiful and the
Damned:
I lay there, frozen with most awful fears, not daring to drag away
my hand; yet ever thinking that I could but stir it one single inch, the horrid
spell would be broken (Fitzgerald, 1922).
Interest in the
phenomenon at the time extended beyond the literary sphere, as evidenced by
Binns clinical description of Sleep Paralysis in 1842, one of the earliest on
record.
The term Sleep
Paralysis, however, was introduced only eighty-five years later, in 1928, by
Wilson to describe attacks of powerlessness that can occur upon awakening.
Two years earlier, in
1926, Adie linked Sleep Paralysis to narcolepsy, an association that persists to
this day.
Before our study, it
was estimated that Sleep Paralysis occurred in 30% to 50% of narcoleptic
patients (Broughton, 1990; Yoss and Daly, 1967).
The prevalence of
isolated Sleep Paralysis (i.e., not related to other medical or psychiatric
disorders) in the general population was less documented:
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The earliest studies
of the phenomenon involving non-narcoleptic subjects were completed in the early
sixties and reported lifetime prevalence rates in narrowly defined populations.
For example, Goode (1962) and Everett (1963) observed rates of 4.7% and 15.4%,
respectively, for self-reported Sleep Paralysis in a population of medical
students.
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Later studies focusing
on specific ethnic groups yielded higher rates; such was the case for Bell et
al. (1984) who noted a prevalence of 41% among Black Americans.
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In a study of adults
living on the northeast coast of Newfoundland, Ness (1978) reported a rate of
62% for attacks of old hag, as Sleep Paralysis is known in that part of Canada;
the occurrence of several episodes, however, was rare and apparently affected
only about 10% of complainers.
In summary, prior to the Sleep-EVAL study, most
of the epidemiological data available on Sleep Paralysis were obtained from
little samples. Consequently, the true prevalence and associated factors of
Sleep Paralysis in the general population remained unknown.
Similarly, the association between Sleep Paralysis and other disorders, with the
exception of narcolepsy,
received little attention:
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Certain case reports
have shown that Sleep Paralysis may lead to psychiatric disturbances (Gangdev.
1996, Gangdev and Ramjee, 1996) or may appear following
posttraumatic
stress disorder.
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Others, still, have
suggested an association with panic attacks (Paradis et al., 1997;Bell et al.,
1986,1988).
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In addition, it has
been found that factors such as stress, fatigue, an irregular life pattern and
sleep deprivation may predispose individuals to Sleep Paralysis (Takeuchi et
al., 1992).
METHOD
A representative sample of the
non-institutionalized general population of Germany and Italy aged 15 years or
over (N=8,085) was surveyed by telephone using the Sleep-EVAL questionnaire and
the Sleep Questionnaire of Alertness and Wakefulness.
RESULTS
Overall, 6.2% (5.7% to 6.7%) of
the sample had experienced at least one Sleep Paralysis episode in their
lifetime.
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Severe Sleep Paralysis (at
least one episode per week) was observed in
0.8% of the sample,
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Moderate Sleep Paralysis
(at least one episode per month) in 1.4%, and
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Mild Sleep Paralysis (less
than one episode per month) in 4.0%.
How frequent is
sleep paralysis?
from Ohayon MM
et al. Prevalence and pathological associations of sleep
paralysis in the general population. Neurology
1999;52:1194-1200.
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Significant predictive
variables of Sleep Paralysis were:
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anxiolytic
medication use,
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memory lapses,
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bipolar disorders,
physical disease,
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hypnopompic
hallucinations,
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non-restorative
sleep and nocturnal leg cramps.
Sleep Paralysis is
frequent in the general population, but less than previously reported.
The disorder is often
associated with a mental disorder.
Users of anxiolytic
medication were nearly 5 times as likely to report Sleep Paralysis, even after
possible effects of mental and sleep disorders were controlled for.
The association
between Sleep Paralysis and hypnagogic and hypnopompic hallucinations underlines
their common etiology.
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Sleep-EVAL
Research
