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Insomnia Definitions
Last edited |
06/13/2006
More than fifty studies of insomnia based on data collected in various
representative community-dwelling samples or populations were published with
highly variable rates
These
surveys provide estimates of the prevalence of insomnia according to four
definitions:
-
insomnia as a symptom,
-
insomnia
as a symptom with daytime
consequences,
-
insomnia as a Global Sleep Dissatisfaction (GSD, Ohayon 1994),
-
insomnia as a diagnosis (according to the psychiatric classification or the
one of the sleep specialists).
The first definition
The first definition
is based on insomnia as a simple criteria.
Four major
criteria are commonly used:
-
Difficulty
Initiating Sleep,
-
Difficulty
Maintaining Sleep,
-
Early Morning
Awakening,
-
Non Restorative
Sleep.
Many
epidemiological used one of these 4 criteria to qualify a subject to be
insomniac.
Early Morning
Awakening is a troublesome symptom: how to define "early" in the general
population?
According to this
classical way, we found in our studies that about one-third of
the general population
presents at least one of them.
These results are
giving an inflating point of view of insomnia in the general population.
The second definition
The second definition
is taking into account the fact that a subject with one the 4 previous criteria
must have also daytime consequences before to be considered insomniac.
According to this way
to define insomnia, many researchers found a
prevalence of insomnia
between
9% and 15% in the general population.
These results are
much lower than those corresponding to the first definition.
The third definition
The third definition
is based on the Global Sleep Dissatisfaction (GSD, Ohayon 1993).
The previous criteria
are not used.
The idea is based on
the paradigm that "insomnia is first defined by the subject himself, by his
persistent complaint (at least 6 months) about the quality or the quantity
of his sleep"
(Ohayon, 1994).
According to this
definition, several studies found a prevalence of
8-18% of the general population.
This prevalence is
close to the one found for the second definition.
However, the subjects
of the second and third definition have not the same characteristics.
The fourth definition
This last
definition gives to the concept of insomnia a status of disease: insomnia is
defined as a complete entity including a set of criteria and different
conditions. Primary and secondary insomnia are distinguished.
The psychiatric and
sleep classifications define different sets of diagnoses.
A Differential
Diagnostic Procedure must be applied in order to validate the positive
diagnosis. This procedure is an elimination procedure aiming to explore all
concurrent diagnoses.
Using this
decision-making
process including a differential diagnosis, we found that the prevalence of
insomnia as a diagnosis (according to the DSM-IV
classification) is 6%.
A part of the
population with GSD is not reaching a diagnosis. This means that a part of the
subjects complaining about their sleep cannot find a place in the Insomnia
Diagnosis Category of the DSM-IV.
Moreover, another
part of the population does not present any criteria of insomnia as defined by
the DSM-IV or the ICSD.
Summary
Conclusions
These four definitions of insomnia
have higher prevalence rates in women than in men.
However, this difference is
disappearing when using a criterion of duration: chronic insomnia (for at least
6 months) is not gender related.
It is why GSD with its definition including a
duration of 6 months is not changing with gender while the other definitions are
doing it.
The prevalence of insomnia symptoms
generally increases with age, while the rates of Global Sleep
Dissatisfaction and Insomnia Diagnoses have
little variation with age.
Moreover, GSD and Insomnia Diagnoses
have a discrepancy of 1 to 5%.
We showed that DSM-IV classification is not
taking into account a certain class of people presenting GSD, but not the 4
insomnia symptoms.
Again, we must stress that someone
may have one or several insomnia symptoms and still be happy with his sleep!
On the contrary, GSD is pointing
directly on the pathological cases.
Future epidemiological studies should focus on the
natural evolution of
insomnia.
Epidemiological genetic links of insomnia are yet to be studied.
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