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Insomnia & Chronic Pain
Last edited |
10/27/2008
Studies on specific chronic painful
physical conditions (CPPC) such as fibromyalgia, arthritis, lower back pain and
headaches showed these individuals often have troubles falling asleep, trouble
staying asleep or wake up unrefreshed
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In pain clinics, as many as 90% of
patients reported at least one sleep disturbance (1,2).
The intensity of sleep
disturbances has also been correlated with greater pain, depression and
disability (1, 3-6).
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Pain
was found to be an important factor related to sleep problems in community-based
studies (7-9).
One Scandinavian community-based study on the elderly (7) showed
that being female, pain, depression and hypnotic-sedative use were factors
significantly related to sleep problems.
Another Scandinavian study on the
elderly (9) reported that pain was a strong factor contributing only to early
morning awakenings.
A Canadian study with subjects 15 years and older (8) found
among other things, that pain and activity limitation were significantly
associated with insomnia in the multivariate model.
However, little
information is available about how chronic pain is related to sleep disturbances
in the general population.
Consequently, we decided to assess the prevalence of chronic painful physical condition in the
general population of five European countries and to examine the place of
chronic painful physical condition in insomnia.
Methods
18,980 participants aged 15 years or older from five European
countries (the United Kingdom, Germany, Italy, Portugal and Spain) and
representative of approximately 206 millions Europeans were interviewed by
telephone.
The interview included questions about sleeping habits, health, sleep
and mental disorders.
Painful physical conditions were ascertained through
questions about medical treatment, consultations and/or hospitalizations for
medical reasons and a list of 42 diseases.
A painful physical condition was
considered chronic when it lasted at least six months.
Insomnia symptoms were
defined as:
present at least 3 nights per week, lasting at least one month ,and accompanied
by daytime consequences.
Results
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The point prevalence of at least one CPPC was set at 17.1% (95% CI:
16.5% to 17.6%) in the sample.
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Difficulty
initiating sleep was found in 5.1% (95% Confidence Intervals: 4.8% to
5.4%) of the sample.
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Disrupted sleep in 7.5% (95% CI: 7.2% to 7.9%)>
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Early
morning awakenings in 4.8% (95% CI: 7.2% to 7.9%).
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Non-restorative sleep in
4.5% (95% CI: 4.2% to 4.8%).
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More than 40% of individuals with insomnia
symptoms reported at least one CPPC.
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CPPC was associated with more frequent
difficulty or inability to resume sleep once awake and a shorter sleep duration.
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In middle-aged subjects (45 to 64 years of age), CPPC was associated with
longer insomnia duration.
At any age, insomnia with CPPC was associated with a
greater number of daytime consequences (average of four consequences) than in
insomnia without CPPC (average of 2.3 consequences).
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In multivariate models, CPPC, especially backaches and joint/articular diseases, were at least as
importantly associated with insomnia than were mood disorders with odds ratios
ranging from 4.1 to 5.0 for backaches and from 3.0 to 4.8 for joint/articular
diseases.
Nighttime awakenings
discussion
This
study examines the relationship between insomnia and chronic painful physical
conditions in the general population of five European countries.
This is the
first community-based study that investigates this association using several
chronic painful physical conditions and insomnia.
Most previous community-based
studies were limited to only one type of pain or to a broad definition of pain
(7-9).
Furthermore, the objective of these studies was not necessarily to
examine how the presence of chronic pain related to insomnia, but had a broader
objective to find associated factors to one of these two conditions (8,19,20).
As a consequence, the importance of pain in insomnia is often overshadowed by a
myriad of other factors.
Moreover, definitions of insomnia used are often
inconsistent and lack crucial information such as the frequency and duration.
It
is difficult therefore to have a clear portrait of the importance of pain in
insomnia.
In
this study, each insomnia symptom had to be present at least three times per
week for at least one month and to have caused at least minimal consequences on
daytime functioning.
Our results show that:
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chronic pain is frequent among
subjects with insomnia: More than 40% of them reported at least one chronic
painful physical condition.
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Chronic pain can be a factor that contributes to the chronicity of insomnia.
We
found longer insomnia duration in our middle-aged subjects with chronic pain
compared to other subjects with insomnia.
This result suggests that, at least in
this specific age group, chronic pain contributes to the maintenance of
insomnia.
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The
relationship between pain and sleep is likely to be bi-directional.
Indeed, if
pain may cause difficulty initiating and/or maintaining sleep, pain intensity
can be as well exacerbated by the lack of sleep.
For example, Affleck et al.
(21) asked to 50 women with fibromyalgia syndrome to keep a diary about their
sleep and pain for 30 days.
They found that a poor night’s sleep was followed by
a day with greater pain and a painful day with a night of poorer sleep.
In this
study, we found that subjects with pain and insomnia experienced greater daytime
consequences of insomnia at any age than when the insomnia subjects had no pain.
Their nighttime sleep duration was also shorter.
We also found that some
individuals compensated this shortening of sleep by napping during the daytime.
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Interestingly, apart from sociodemographic determinants,
associated factors for
each insomnia symptom were about the same. Noteworthy, backaches and joint/articular
disease were at least as importantly associated with insomnia as were mood
disorders.
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The
interactions between insomnia, pain and mental disorders deserve some attention.
Interestingly, anxiety disorders did not make independent contributions to any
insomnia symptom in the multivariate models.
Part of the explanation can be in
the high co-morbidity between anxiety and mood disorders, which played a greater
role than anxiety disorders.
Another possibility lies in the definition of
insomnia we adopted.
Mostly, epidemiological surveys defined insomnia as the
presence of the symptoms at least three nights per week regardless of the
duration and daytime consequences.
Obviously, this definition increases
prevalence of insomnia symptoms.
Mildest manifestations of insomnia could be
more frequently related to anxiety disorders.
Conclusions
CPPC is associated with a worsening of
insomnia on several aspects: a greater number of insomnia symptoms, more severe
daytime consequences and more chronic insomnia situation.
CPPC plays a major
role on insomnia.
Its place as major contributive factor for insomnia is as much
important as mood disorders.
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