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Epidemiology of Insomnia
Last edited |
10/22/2008
Sleep medicine is a young discipline and
the epidemiology of insomnia is still in its infancy
The youthfulness of sleep medicine is evident from the lack of
proper definition of insomnia and how insomnia should be assessed in a general
population so that it makes a meaningful sense at both epidemiological and
clinical levels.
The first epidemiological study on insomnia was published less
than 25 years ago [1].
From that time, the field has flourished and one can find more
than 50 epidemiological studies on insomnia from different parts of the world
[2].
In early years of insomnia epidemiology, researchers came up with
very high prevalence of insomnia symptomatology (up to 40% of the population in
some studies).
Narrower definitions in terms of severity and frequency of
insomnia decreased the prevalence to 15-20% of the population [2].
Yet, no consensus exists between the classifications on how to
define insomnia in terms of symptomatology, frequency and severity.
For example, in the DSM-IV, insomnia is defined as a complaint of
difficulty initiating or maintaining sleep or of non-restorative sleep that
lasts at least one month and causes significant distress or impairment in the
individuals functioning.
The International Classification of Diseases defines
insomnia as difficulty initiating or maintaining sleep occurring at least 3
nights per week for at least one month.
Finally, the International
Classification of Sleep Disorders defines insomnia as an almost nightly
complaint of an insufficient amount of sleep or not feeling rested after the
habitual sleep episode.
In its mild form, the individual may have little or no
evidence of impairment in his or her functioning.
Consequently epidemiologists
are using different definitions that lead to different prevalence figures and
render very difficult the comparison between the different studies.
This is partly why epidemiological studies are so important and
necessary.
Nosologically, they provide valuable information on how a clinical
description fits a general population and they help to point out the strengths
and the gaps in existing classifications.
For example, a common belief,
confirmed by several studies, is that sleep complaints are increasing with age
[2].
However, there is a growing number of epidemiological studies that are
showing the relationship aging / insomnia is not linear but the result of a
combination of factors [3], [4], [5].
In this specific population, a tight
investigation of sleep is primordial before concluding the presence of a sleep
disorder.
They demonstrate that sleep complaints are mostly the result of
co-morbid medical conditions, psychiatric disorders and related health burdens
rather than age per se.
The difficulty in studying insomnia in the general population is
increased by the fact that insomnia can be a symptom or a diagnosis and the
distinction between the two is challenging in the general population.
Insomnia
can be the symptom of an organic disease, a psychiatric illness or a sleep
disorder such as obstructive sleep apnea syndrome or restless legs syndrome but
it can be also a diagnosis.
Most epidemiological studies have not attempted to evaluate the
diagnostic issues of subjects with insomnia and have limited their analyses to
the report of associations.
There is a need for valid diagnostic tools of sleep disorders
that can be used in the general population.
Epidemiological studies are also useful to determine sleep-wake
schedule norms in the general population.
Deviations from these norms represent
abnormalities that need to be further investigated.
Research that analyzes these
norms are still scant although this is crucial information.
Epidemiology provides valuable information concerning the natural
evolution of sleep disorder.
Currently however, few such studies exist [11],
[12], [13].
Roberts et al. [14] have done a one-year follow-up study with 4,175
adolescents aged between 11 and 17 years.
They demonstrated that insomniac
adolescents had an average odds ratio of 2.5 of impaired functioning one year
later.
Epidemiology bestows portraits of specific populations at a given
time.
It provides not only clues about the health needs of insomnia individuals
but it also shows where are the lacks in health care systems in terms of
recognition of insomnia and adequacy of the medical response.
Prescribed drugs users had more severe insomnia and greater
disability than others and participants that used alcohol as sleep-aid had
greater daytime sleepiness.
Assessment of adverse events and daytime consequences of insomnia
provides important information to improve work conditions in specific
populations.
Two articles
deal with these questions:
-
Akerstedt et al. [16] using
a huge sample of 47,860 employees related sleep disturbances to hectic work,
physically strenuous work and shift/night work.
-
In another study, Ohayon et al.
[17] investigated the effects of work schedule in the employees of a hospital.
They underlined that rotating daytime shifts had adverse events on sleep.
It
appeared that it was not the bedtime variation but the fluctuation of the wake
up time that had more negative impacts on daytime functioning and sleep.
Repeatedly in the past decade, researchers involved in the field
of sleep medicine have reported the lack of medical response despite the fact
that individuals with insomnia are huge health care consumers [18].
The truth is
that sleep medicine is an underprivileged field in medical education with few
hours devoted to the teaching of sleep disorders.
The study of Ohayon and Hong
[9] performed in the general population of South Korea illustrates this aspect.
They found that 5% of their sample has an insomnia disorder diagnoses but of
those only 6% of them have sought medical help for their insomnia.
In South
Korea, home remedies were the most popular method to treat insomnia.
Even in
Western countries only 25% to 30% insomnia sufferers consulted about their
problem [19], [20].
Often patients do not see sleep problems as an illness and
doctors and patients effectively conspire to ignore sleep problems.
References
[1] Karacan I, Thornby JI,
Anch M, et al. Prevalence of sleep disturbance in a primarily urban Florida
county. Soc Sci Med 1976;10: 239-244.
[2] Ohayon MM.
Epidemiology of Insomnia: What We Know and What We Still Need to Learn. Sleep
Medicine Review. 2002; In press.
[3] Bliwise DL, King AC,
Harris RB, Haskell WL. Prevalence of self-reported poor sleep in a healthy
population aged 50-65. Soc Sci Med. 1992;34:49-55.
[4] Yeo BK, Perera IS,
Kok LP, Tsoi WF. Insomnia in the community. Singapore Med J 1996;37:282-284.
[5] Ohayon MM, Zulley J,
Guilleminault C, Smirne S, Priest RG. How age and daytime activities are related
to insomnia in the general population? Consequences for elderly people. J Am
Geriatr Soc 2001; 49:360-366.
[6] Vitiello MV, Moe
KE, Prinz PN. Sleep complaints co-segregate with illness in older adults:
Clinical research informed by and informing epidemiology studies of sleep. J
Psychosom Res 2002; vol(iss):pages.
[7] Guilleminault C,
Palombini L, Poyares D, Chowdhuri S. Chronic Insomnia, post menopausal women,
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Psychosom Res 2002; vol(issue):pages.
[8] Guilleminault C, Palombini
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J Psychosom Res 2002; vol(issue):pages.
[9] Ohayon MM, Hong SC.
Prevalence of Insomnia and Associated Factors in South Korea. J Psychosom Res
2002; vol(iss):pages.
[10] Thorleifsdottir
B, Bjornsson JK, Benediktsdottir B, Gislason TH, Kristbjarnarson H. Sleep and
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[11] Ford DE, Kamerow DB.
Epidemiologic study of sleep disturbances and psychiatric disorders. An
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[12] Breslau N, Roth T,
Rosenthal L, Andreski, P. Sleep disturbance and psychiatric disorders: a
longitudinal epidemiological study of young adults. Biol Psychiatry 1996;
39:411-418.
[13] Roberts RE, Shema SJ,
Kaplan GA, Strawbridge WJ. Sleep complaints and depression in an aging cohort: A
prospective perspective. Am J Psychiatry 2000;157:81-88.
[14] Roberts RE,
Roberts CR, Chen IG. Impact of Insomnia on Future Functioning of Adolescents. J
Psychosom Res 2002; vol(iss):pages.
[15] Roehrs T, Hollebeek E,
Drake C, Roth T. Substance Use For Insomnia in Metropolitan Detroit. J Psychosom
Res 2002; vol(iss):pages.
[16] Εkerstedt T,
Fredlund P, Gillberg M, ? . Work load and work hours in relation to disturbed
sleep and fatigue in a large representative sample. J Psychosom Res 2002;
vol(iss):pages.
[17] Ohayon MM, Lemoine
P. Prevalence and Consequences of Sleep Disorders in a Shiftworker Population. J
Psychosom Res 2002; vol(iss):pages.
[18] Chilcott LA and Shapiro CM.
The Socioeconomic
impact of insomnia: An overview. PharmacoEconomics 1996: 10 Suppl. 1: 1-14
[19] Ancoli-Israel S,
Roth T. Characteristics of insomnia in the United States: results of the 1991
National Sleep Foundation Survey. I. Sleep 1999;22 Suppl 2:S347-353.
[20] Ohayon MM. Prevalence of
DSM-IV diagnostic criteria of insomnia: Distinguishing between insomnia related
to mental disorders from sleep disorders. J Psychiatr Res 1997; 31: 333-346.
[21] Bliwise DL. Sleep
Apnea, APO-E4, and Alzheimer's Disease: 20 Years and Counting? J Psychosom Res
2002; vol(iss):pages.
Content
of this page is extracted from
Ohayon MM. Conference, Sleep Epidemiology Center, Palo Alto, 2002.
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