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2008
Paper 3615 307
ABSTRACT
ORIGINAL ARTICLE
An international survey of
sleeping problems in the
general population
D. Léger
a
, B. Poursain
b
, D. Neubauer
c
and
M. Uchiyama
d
a
Centre du Sommeil et de la Vigilance, Hôtel-Dieu de Paris,
Université Paris Descartes, Paris, France
b
TNS Healthcare – International Department, Paris, France
c
Sleep Disorder Center, Johns Hopkins University, Baltimore, MD, USA
d
Department of Neuropsychiatry, Nihon University School of Medicine,
Tokyo, Japan
Address for correspondence: Dr. D. Léger, Centre du Sommeil, Hôtel-Dieu de Paris, APHP,
Université Paris Descartes, 1 Place du Parvis Notre-Dame, 75151 Paris Cedex 04, France.
Tel: +33 1 42 34 82 43; Fax: + 33 1 42 34 82 27; damien.leger@htd.aphp.fr
Key words: Multinational – Prevalence – Sleep disorders – Survey – Treatment
Introduction
Insomnia can be defined as difficulty falling asleep,
difficulty maintaining sleep, early-morning awakening
and non-restorative sleep with associated daytime
consequences
1–4
. However, the wide range of distinctive
etiologies and varying degrees of sleep disturbance often
make classification difficult. Depending on definition
and regions, up to one-third of the population may
exper ience insomnia symptoms
5–13
. For example, on
a large cross-sectional telephone survey conducted in
a representative sample of the populations of France,
the UK, Germany, Italy, Portugal and Spain, difficulty
initiating or maintaining sleep for at least three nights
Objective: This international omnibus survey
investigated the prevalence and characteristics of
sleep problems, as well as strategies for resolving
sleep problems, in the general population of the
USA, France, Germany, Italy, Spain, the UK and
Japan.
Research design and methods: A representative
sample of the general population aged ≥
15 years
was recruited from each country. Questions
focused on the nature of sleeping problems,
the impact of problems on daily functioning
and behavior with regard to resolving sleeping
problems.
Results: A total of 10
132 individuals were
included in this survey. The prevalence of sleeping
problems was 56% in the USA, 31% in Western
Europe and 23% in Japan. Most individuals with
sleeping problems considered these to have an
impact on their daily functioning, with family
life most affected in the Western European
sample, personal activities in the US sample and
professional activities in the Japanese sample.
Almost half of individuals with sleep problems
had never taken any steps to resolving them,
and the majority of respondents had not spoken
with a physician about their problems. Of those
individuals who had consulted a physician, drug
prescriptions had been given to approximately
50% in Western Europe and the USA and 90% in
Japan.
Conclusions: Sleeping problems continue to
present a considerable burden across Western
Europe, the USA and Japan. Despite this, they are
under-reported and under-treated, with almost
half of affected individuals not taking any steps to
resolve their sleeping problems.
CURRENT MEDICAL RESEARCH AND OPINION®
VOL. 24, NO. 1, 2008, 307–317
© 2008 LIBRAPHARM LIMITED
0300-7995
doi:10.1185/030079907X253771
All rights reserved: reproduction in whole or part not permitted
308 Omnibus: sleep problems in the general population © 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1)
per week was reported by 27% of the sample; however,
half of these individuals did not have a diagnosis of a
sleep or mental disorder as defined by the Diagnostic
and Statistical Manual of Mental Disorders – 4th
edition (DSM-IV)
7
. While data from Asian populations
are limited, the overall prevalence of insomnia in a
representative sample from the general population of
Japan was 21.4% in the month preceding the survey,
mainly attributed to difficulty maintaining sleep and
falling asleep
12
. Multiple logistic regression analysis
showed that advanced age, being unemployed, lack
of habitual exercise, perceived poor health, and stress
were associated with a higher likelihood of insomnia.
Sleep disturbances have a potentially serious health
impact. An analysis of 28 epidemiological studies found
that insomnia is associated with psychological disorders,
being a risk factor for depression, anxiety disorders, alcohol
and drug abuse, and suicide
14
. This supports the findings
of a number of other studies in various populations
9,15,16
.
Furthermore, there is at the very least an association
between insomnia and decreased immune function
14
,
and a possible association with cardiovascular disease
16
.
Several studies have shown that daytime sleepiness is a
risk factor for motor vehicle accidents
9,17
and may have
considerable socio-professional con sequences, including
increased absenteeism from work
18,19
.
Health-related quality of life (HRQOL) is nearly
always affected in patients experiencing excessive day-
time sleepiness or difficulty initiating or maintaining
sleep, according to the findings of the large Sleep Heart
Health Study
20
. In this study, HRQOL was evaluated with
the generic Short-Form 36 (SF-36) Health Outcomes
Questionnaire in over 5800 individuals in the general
US population. Impairments in HRQOL associated with
subjective sleep symptoms were found to be of a similar
degree to other chronic diseases. Likewise, individuals
self-reporting insomnia for at least three nights a week
over a month had statistically lower scores on all subscales
of the SF-36 compared with individuals without sleep
problems
21
. These findings support those of a French study
showing that, even after excluding patients with DSM-IV
criteria for anxiety or depression, insomnia is associated
with reduced emotional and mental health status
22
. In this
analysis, reductions in SF-36 scores correlated with the
severity of insomnia.
The impact of insomnia on health and HRQOL
translate into economic consequences. Walsh and
Engelhardt estimated the direct costs of insomnia (costs
of substances used to treat the condition and related
healthcare services) in the USA were almost US$14
billion
in 1995, much of which was attributed to nursing home
care for the elderly
23
. In France in 1995, estimates of the
direct costs of insomnia were US$2
billion
24
. It should be
noted that these values do not take into consideration the
indirect or related costs of insomnia such as reduced work
productivity or increased likelihood of accidents, which
would be expected to at least double the economic burden
of sleep disorders
25
. Indeed, a French study comparing
individuals with severe insomnia with good sleepers
matched for professional activities and work schedules
found that those with sleep problems missed twice as
many workdays during the previous year
18
. Furthermore,
individuals with insomnia reported more difficulties with
concentration and an increased frequency of work-related
accidents.
While sleep disturbances clearly contribute to a
significant health and economic burden, evidence
suggests that they are under-reported and under-treated.
In an omnibus consumer survey conducted in France,
Germany, Italy and the UK, it was found that 37% of
respondents with insomnia took no action to resolve
it at all, while 10% used over-the-counter remedies
and 13% adopted non-pharmacological measures
26
. A
recent survey conducted in Western Europe, the USA
and Japan demonstrated that the burden of insomnia
on sufferers is considerable, although only 3% (Japan)
to 22% (France) of individuals consulted a physician
about their symptoms
27
. However, if insomnia and its
consequences on daytime functioning are to be better
understood, there is clearly a lack of understanding on
the strategies used by patients with insomnia to cope
with sleep disorders and daytime impairment.
Based on these preliminary data, we wanted to deepen
our knowledge of insomnia in a more extensive and world-
wide representative sample. The goal of this international
omnibus survey was to further investigate the prevalence
and characteristics of sleep problems, as well as strategies
for resolving them in the general population of the USA,
France, Germany, Italy, Spain, the UK and Japan.
Methods
A representative sample of the general population aged
≥
15 years was recruited from the USA, France, Germany,
Italy, Spain, the UK and Japan in October 2005. Data
were collected by computer-assisted telephone interviews
as part of multi-client monthly omnibus surveys
conducted by LH2 in France, TNS in Germany, TRIBE
in Italy, TNS in Spain and QRS in the UK.*
* TNS (Taylor–Nelson Sofres group), www.tnsglobal.com; TNS Healthcare is a sector of the TNS group, www.tns-healthcare.
com; LH2, previously named Louis Harris France, is a full-service MR company based in Paris, www.LH2.fr; TRIBE special-
izes in medical fieldwork and is based in Milan, no specific website; QRS is a fieldwork company based near London and
specializes in quantitative data collection, www.qrs-research.co.uk; NRC (Nippon Research Center) is a member of Gallup
International Network (GIA), www.nrc.co.jp/english/.
© 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1) Omnibus: sleep problems in the general population Léger et al. 309
In the USA, data were collected via an online
panel facilitated by TNS, and in Japan via a postal
questionnaire facilitated by NRC. These local fieldwork
agencies conducted this study according to international
standards. TNS was selected because it has offices and
a good reputation in poll studies in France, Germany,
Spain, USA and Japan. TNS was not represented in
Italy and the UK but has experience in the field with
the selected companies TRIBE and QRS.
For the telephone interviews, an automated dialing
system was used to randomly select telephone numbers
based on files stratified according to region and city
size. Quotas on age, gender and the employment status
of the head of the family were applied. Recruitment of
participants for the online and postal panels were based
on representative files of national populations. Ethical
rules regarding confidentiality of data were strictly
observed in each country and guaranteed by each local
fieldwork agency. Any third parties did not have access
to respondents’ identities.
A semi-structured omnibus survey, consisting of a
standardized 10–15-minute interview, was conducted
over the telephone by professional interviewers, or
was provided as an online or postal questionnaire
on a weekly or monthly basis. The questions were
identical regardless of whether they were answered
over the telephone, via the internet or on paper and
the questions did not include features that would bias
the responses. Respondents were eligible to complete
the survey if they answered to the following question
in the affirmative: ‘Have you suffered from sleeping
problems in the past 12 months?’ The questionnaire
asked respondents about the nature of their sleeping
problems in terms of symptoms, frequency and
duration. Questions also focused on which sleeping
symptoms caused the greatest degree of concern,
how sleeping problems had evolved over time and the
impact of sleeping problems on daily functioning.
Insomnia was defined as having at least one sleep
problem (difficulty falling asleep, difficulty staying
asleep due to night-time awakenings, waking up early
and not being able to go back to sleep, poor quality of
sleep) experienced at least several times per week for
more than 1 year, with daytime consequences. People
who have been diagnosed with sleep apnea or restless
legs syndrome were excluded.
Behavior regarding resolving sleep problems was
also investigated: respondents were questioned as to
whether they had consulted a physician about their
sleep problems, or whether they had received a drug
prescription for their symptoms. Questions included:
‘have you ever talked about these sleep problems with
a physician?, ‘what type of physician did you consult?’,
did the physician prescribe you a drug for your
sleeping problems?’, ‘did you take the drug prescribed
by the physician?’, and ‘for how long did you take
it?’ The level of satisfaction with treatment for sleep
problems was assessed on a numerical 10-point rating
scale, with 1 representing ‘not satisfied at all’ and 10
indicating ‘very satisfied’. There was no question about
continuous versus intermittent use.
Respondents were also asked whether they found
sleep problems to be troublesome (phrased as
whether they were ‘very bothered’, ‘bothered’, or ‘not
bothered’).
Questionnaires were translated in each country and
care was taken not only with linguistic aspects (checked
by TNS writers) but also with sleep issues (validated
by sleep specialists from each country considered). A
special meeting between specialists at the beginning of
the study was devoted to these issues.
Different channels were used to interview people
depending of the country.
Only face-to-face omnibuses are available in Japan ●
because phone and web interviews are not accepted
by the public.
Web interviews are particularly suitable for the ●
American market because of the large internet
penetration in all age brackets (allowing large size
samples).
Phone interviews were the best solution in Western ●
Europe because of the low penetration rate of the
internet in the elderly population (which is the
population having sleeping disturbances the most
frequently) and a lower cost/effectiveness ratio for
face-to-face methodology in this case.
Categorical values are presented as percentages with
95% confidence intervals (CIs). A chi-squared analysis
of survey results was conducted to assess relationships
between respondent characteristics and the impact
of their sleep problems on daily functioning or the
likelihood of receiving a drug prescription to treat sleep
symptoms as well as to identify country specificities.
Data were extrapolated to the population of
each country (aged ≥
15 years), based on 2005 USA
Census Bureau data (USA: 234
934
412; France:
49
498
357; Germany: 70
586
441; Italy: 50
017
532;
Spain: 34
531
882; the UK: 49
721
174; and Japan:
109
221
888).
A weighting was performed to adjust our sample to the
structure of each population at a national level, in terms
of age, gender and household socioeconomic level.
Results
Population characteristics
The study population was composed of a total of
10
132 individuals (3962 from the USA, 1002 from
310 Omnibus: sleep problems in the general population © 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1)
France, 1001 from Germany, 1000 from Italy, 1002
from Spain, 1000 from the UK and 1165 from Japan),
who were representative of the national population
of their respective countries in terms of region, age,
gender and head of family occupation.
Prevalence of sleeping problems
The overall prevalence of perceptions of sleeping
problems was the greatest in the USA (56%; 95% CI
54–58%). In Western Europe, the prevalence was 34%
in France (95% CI 31–37%), 33% in Germany (95% CI
30–36%), 30% in Italy (95% CI 27–33%), 23% in Spain
(95% CI 20–26%) and 36% (95% CI 33–39%) in the
UK, while the prevalence in Japan was 23% (95% CI
21–25%).
Subjects reporting sleep apnea or restless legs
syndrome were excluded from the study:
6% of the population in Western Europe, 11% in ●
the US, 3% in Japan declared that they suffered
from sleep apnea.
11% of the population in Western Europe, 17% in ●
the US, 2% in Japan declared that they suffered
from restless legs syndrome.
The number of patients with insomnia per se (based on
at least one sleep problem experienced at least several
times per week for more than 1 year, with daytime
consequences) can be evaluated to be 28%, 39% and
21% of the European, US and Japanese respondents,
respectively who reported having sleeping problems
during the previous 12 months (excluding sleep apnea
and restless legs syndrome).
The gender and age characteristics of the total and
sleeping problems groups are shown in Table 1.
The impact of age on the prevalence of insomnia
differed according to region: in Japan, the highest
prevalence of sleeping problems was in those aged
55–64 years (25%), while in Western Europe and the
USA, the highest prevalence was in those in the 35–44
year age group (22% and 20%, respectively).
Types of sleep problem
Of the individuals reporting sleep problems (excluding
sleep apnea or restless legs syndrome), difficulty
maintaining sleep was the most common complaint
in the USA and Western Europe, but problems with
sleep induction was most common in Japan. More
respondents from the USA reported poor sleep quality
than those from other regions (Figure 1). A total of 43%
(95% CI 40–46%), 62% (95% CI 60–64%), and 48%
(95% CI 42–54%) of participants in Western Europe,
the USA and Japan, respectively, reported more than
one sleeping problem, with 17% (95% 15–19%), 26%
(24–28%), and 11% (95% CI 7–15%) of respondents
experiencing difficulty with all aspects: sleep induction,
sleep maintenance and quality of sleep.
In individuals reporting more than one sleep
problem, poor sleep maintenance was most common
in the USA, while difficulty getting to sleep was more
common in Japan. Both problems were reported to a
similar extent by European respondents. Conversely,
poor sleep quality was not as common as the other two
sleep parameters in any region.
Development of sleep problems
In participants with sleep problems, 59% (95% CI
56–62%) of respondents from Western Europe, 52%
(95% CI 50–54%) of those from the USA and 85%
(95% CI 81–89%) from Japan reported that their main
sleep problem had not changed in severity over time. In
participants who did report a change in their main sleep
problem, this was considered to be a deterioration by
46% (95% CI 42–50%) of European respondents, 78%
Table 1. Gender and age characteristics of the total population and of the sleeping problems group
Participants (%)
ASU
(n = 3962)
Western Europe
(n = 5005)
Japan
(n = 1165)
15 % ,redneg elaM (44) 84 (39) )14( 54
% ,egA
)31( 51 )51( 41 )41( 51 sraey 42–51
)41( 61 )31( 81 )91( 91 sraey 43–52
)31( 61 )22( 91 )02( 91 sraey 44–43
61 )71( 71 sraey 45–44 (21) )41( 61
91 )51( 41 )31( 31 sraey 46–45 (25)
≥
)12( 81 )51( 91 )71( 81 sraey 56
Significant differences
(
CI = 95%
)
between the total population. The subgroup with sleeping problems have been emboldened
© 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1) Omnibus: sleep problems in the general population Léger et al. 311
(95% CI 75–81%) of US respondents and 15% (95% CI
9–21%) of Japanese respondents. The nature of the
predominant symptom remained the same in most cases.
Frequency of sleep problems
Most individuals from Western Europe and the USA
reporting sleep problems experienced symptoms at
least several times per week. In Japan, problems were
less frequent (Figure 2). The majority of respondents
from each region indicated that they had experienced
symptoms for at least 1 year (mean of 6 years, 5 years
and 4 years in Western Europe, the USA and Japan,
respectively). Despite having experienced sleeping
problems for more than 1 year, only 51%, 55% and 52%
of respondents in Western Europe, the USA and Japan,
respectively considered their problems to be chronic
rather than occasional. However, if a chronic sleep
problem is defined as having experienced a symptom
for ≥
1 month, 88% (95% CI 86–90%) of participants
from Western Europe, 93% (95% CI 90–96%) from
Japan and 93% (95% CI 92–94%) from the USA would
have been categorized with chronic sleep problems.
This was true for all aspects of sleep disorders (sleep
induction, maintenance and quality).
Impact of sleep problems
Most individuals with sleep problems considered these
to have an impact on their daily functioning (Figure 3),
Figure 1. Types of sleep problems among individuals reporting sleep problems over the previous 12 months. Answers were in
response to the following question: ‘What sleep problem symptoms do you currently suffer from?’. p-values for trends: USA vs.
Western Europe (0.025 < p < 0.05), Western Europe vs. Japan (0.05 < p < 0.1), and USA vs. Japan (
p < 0.005)
57
78
52
55
75
33
69
63
31
0
20
40
60
80
100
Sleep induction problems Sleep maintenance
problems
Poor sleep quality
Sleep problem
Respondents (%)
USA (n = 1637) Western Europe (n = 1306)
Japan (n = 259)
Figure 2. Frequency of sleep problems among individuals reporting sleep problems over the previous 12 months. Answers were in
response to the following question: ‘How often do you have these sleeping symptoms?’. p < 0.005 for between-region differences
4.8
14.0
26.6
13.6
19.0
31.0
52.0
35.0
27.0
29.6
30.0
15.4
0
10
20
30
40
50
60
70
80
90
100
USA
(n = 1637)
Europe
(n = 1306)
Japan
(n = 259)
Region
Respondents (%)
Occasionally A few times per week
A few times per month Every night
312 Omnibus: sleep problems in the general population © 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1)
including family life, personal activities, professional
activities and social relationships (Figure 4). In Japan,
professional activities were the daily function aspect
that were most affected by sleep problems, while
family life was most affected in Western Europe and
personal activities were most affected in the USA. Not
surprisingly, the impact of sleep problems on daily
functioning was linked to the number of symptoms
reported by the individual: 91% (95% CI 88–94%)
of US respondents experiencing sleep induction,
maintenance and quality problems considered sleep
to impact their daily function, as did 86% (95% CI
73–99%) of Japanese respondents and 62% (95% CI
56–68%) of Western European respondents.
Chi-squared analysis showed that there were
several demographic or behavioral characteristics that
were common to individuals across the regions who
perceived their sleeping problems to impact their daily
function (Table 2). These included having several
symptoms, experiencing symptoms quite often, and
suffering from sleep-related comorbidities.
The most frequent disorder caused by sleep problems
was physical fatigue, either in the morning or later in
the day. Bad mood, poor concentration and mental
fatigue were also commonly considered to be caused
by sleep problems.
Individuals with sleep problems often had other
comorbidities that may have been associated with
their sleep. In all three regions, stress and overworking
was the most common comorbidity. In the USA,
being overweight was also a dominant comorbidity,
with joint pain/rheumatism, anxiety/anguish and
Figure 4. Perceived consequences of sleep problems on specific aspects of daily functioning. Answers were in response to
completing the following statement: ‘Would you say that your sleep problems impact…?’ p < 0.005 for between-region differences
for each aspect of daily functioning (‘Family life’, ‘Personal activities’, ‘Professional activities’, ‘Social relationships’)
Figure 3. Perceived consequences of sleep problems on daily functioning. Answers were in response to completing the following
statement: ‘Would you say that your sleep problems impact your daily functioning…?’ p < 0.005 for between-region differences
18 18
12
61
36
46
18
27
37
3
19
5
0
10
20
30
40
50
60
70
80
90
100
USA
(n = 1637)
Western Europe
(n = 1306)
Japan
(n = 259)
Region
Respondents (%)
A lot Somewhat
Not really Not at all
57
69
51
44
0
44
40
42
36
14
46
20
60
29
1
0
10
20
30
40
50
60
70
80
90
100
Family life Personal
activities
Professional
activities
Social
relationships
Don't know
Aspects of daily functioning
Respondents (%)
USA (n = 1297) Western Europe (n = 712) Japan (n = 151)
© 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1) Omnibus: sleep problems in the general population Léger et al. 313
nervousness/irritability occurring comparatively
frequently in Western European respondents. The two
most common comorbidities in Japanese respondents
were stress/overworking and nervousness/irritability,
although over a quarter of Japanese respondents did
not have an associated comorbidity.
Treatment for sleep problems
Almost half of individuals with sleep problems had never
taken any steps to resolve their sleeping problems. The
majority of respondents reporting a sleep disorder had not
spoken to a physician about it (47% [95% CI 44–50%] in
Western Europe, 65% [95% CI 63–67%] in the USA and
67% [95% CI 61–73%] in Japan). Of those respondents
who had consulted a physician with regard to their sleep
problems, approximately 50% in Western Europe and
the USA received a drug prescription, compared with
90% of respondents in Japan. Of those who received a
prescription drug, the average length of time taking this
treatment was 2 years in the USA, 3 years in Japan and
4 years in Western Europe. In all, 29% of patients in
Western Europe, 10% in the US, and 24% in Japan were
taking the last treatment prescribed for more than 5 years.
Prescription drugs were taken more frequently across
all regions than drugs advised by a pharmacist, drugs
without any medical advice or treatments other than
drugs. In Western Europe, significantly more individuals
with sleep maintenance problems were not receiving any
form of treatment compared with other symptoms (
p <
0.05). In contrast, in the USA, more individuals with
sleep quality symptoms were not receiving treatment
(
p < 0.05). Chi-squared analysis showed that there were
several demographic or behavioral characteristics that
were common to individuals across the regions who had
a medical treatment prescribed for their sleep problems
(Table 3). These included having several symptoms,
considering their sleep problems to be chronic, and
suffering from sleep-related comorbidities. Another
predictive factor was using other strategies to resolve
sleep problems, whether this be non-prescription drugs or
other remedies. While individuals in Western Europe or
the USA were more likely to have experienced a negative
change in their symptoms over time, Japanese individuals
were more likely to have experienced a positive change in
their symptoms.
Discussion
The magnitude of sleep problems in three economically
developed parts of the world (Western Europe, Japan and
USA) is clearly shown in this study. When extrapolated
to the general population, this indicates that 131.3
million
people in the USA (±
1.5%), 82.3
million people in
Western Europe (±
1.3%), and 25.6
million people in
Japan (±
2.4%) have had sleep problems within the past
12 months. Even with a more stringent definition of
insomnia , it still concerns 38.1
million people in the USA
(±
1.1%), 18.8
million people in Western Europe (±
0.7%)
and 5.2
million people in Japan (±
1.2%). Clearly Japan
appears to be less effected by sleep problems than the two
other continents. It could be speculated that the lower
prevalence in Japan may be a function of under-reporting
Table 2. Chi-squared analysis showing statistically significant demographic or behavioral characteristics of individuals who
perceive their sleep problems to impact on their daily functioning
USA Western
Europe
Japan
Age ≥
65 years
Female
noitapucco na evaH
Poor sleep quality
Have difficulty falling asleep
Experience several sleep symptoms
Experienced an evolution in sleep problems
Experience problems as a consequence of insomnia
Experience sleep problems quite frequently
Consider their sleep problems to be chronic
Experience comorbidities as a result of sleep problems
Have consulted a physician about sleep problems
smelborp peels tuoba tsirtaihcysp a detlusnoc evaH
Take a prescribed medication or another means of resolving their sleep problems
noitacidem debircserp-non a esU
314 Omnibus: sleep problems in the general population © 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1)
because of the possible cultural reticence among Japanese
people to associate sleep problems and psychiatric
disorders
27
. Indeed, the relatively short mean time spent
in bed (6.5
h) reported previously in the Japanese adult
population
13
might lead to reduced difficulty maintaining
sleep, as bedtime restriction has been shown to improve
sleep efficiency
28
. The prevalence of insomnia we found
in the Japanese is consistent with that found by Doi
and colleagues in a nationwide sample of 2800 subjects:
17.3% in males and 21.5% in females
29
. However in
young people, Kaneita and colleagues recently found in
a survey of 102
451 Japanese adolescents that insomnia
concerns 23.5% of the sample, which was more than in
our study
30
. Interestingly, the reported prevalence in this
study is notably greater than in the previous survey (37%,
27%, 28%, and 6.6% in France, Italy, the USA and Japan,
respectively)
27
. The relatively dramatic difference in the
prevalence in the USA in this study may be a consequence
of an increased awareness and perception of sleeping
problems in the general population due to national public
and private education on sleep disorders; however, it is
interesting that it appears to have had a limited effect on
physician consultation rates or prescriptions. Although
cultural factors are likely to influence responses, the
prevalence in the USA obtained in this study does not
differ substantially from the findings of previous surveys,
in which approximately a third to one-half of respondents
reported sleep disturbances. The 2002 National Sleep
Foundation poll reported that 58% of adults said that they
had at least one symptom of insomnia at least a few times
per week. However, these people did not necessarily
experience daytime sleepiness as a consequence of
their insomnia. The higher prevalence in the Japanese
population in this study compared with the previous
survey may be linked to the inclusion of individuals aged
≥
65 years in the Japanese sample in this study (who were
not included in the previous sample). The prevalence
of sleep problems obtained in the present survey is also
consistent with the findings of a previous epidemiological
study including 3030 participants recruited throughout
Japan
12
. In Western Europe, there has only been a limited
change in the prevalence of insomnia between this survey
and the previous one and the frequency of sleep disorders
and insomnia found in this study are similar to those
reported in previous epidemiological studies carried out
in Western Europe (19–25% for sleep disorders, 9–12%
for severe insomnia)
6,10,31
.
The distribution of sleep problems according to age
varied between regions; in Japan, but not in Western
Europe and in the USA, respondents aged ≥
65 years
experienced a high prevalence of problems. This is not
consistent with previous studies which regularly found
higher percentages of sleep problems in the elderly. We
have no explanation for this unusual result. Conversely
the fact that more females than males reported sleep
problems is consistent with previous studies investigating
the epidemiology of sleep disorders
5–10,32
.
The most frequently reported sleep problem varied
according to region: in Japan, sleep induction was the
most prevalent problem, as was found by Doi et al.
29
,
Table 3. Chi-squared analysis showing statistically significant demographic or behavioral characteristics of individuals who
are prescribed a medical treatment for their sleep problems
nretseW ASU
Europe
Japan
Age ≥
65 years
Female
noitapucco na evaH
Have difficulty falling asleep
sgninekawa emit-thgin ecneirepxE
Experience several sleep symptoms
smelborp peels ni noitulove na decneirepxE
Experienced a negative evolution in sleep problems
Experienced a positive evolution in sleep problems
Experience an impact on daily functioning
Experienced problems as a consequence of insomnia
Have frequent and long-lasting sleep problems
Consider their sleep problems to be chronic
Experience comorbidities as a result of sleep problems
Use sleep remedies frequently
Use a non-prescribed medication
noitacidem fo snaem rehto esU
© 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1) Omnibus: sleep problems in the general population Léger et al. 315
while in Western Europe and the USA, more individuals
had problems with sleep maintenance. Taken together,
it is clear that the most prevalent global sleep problem is
sleep maintenance, with 75
million people in the USA,
51
million people in Western Europe and 15
million
people in Japan likely to report difficulties with sleep
maintenance. The majority of respondents reported
problems with more than one sleep parameter. Sleep
problems changed in severity over time in just under
half of participants in each region: in Western Europe
and the USA, a considerable proportion of respondents
considered that their sleep had deteriorated, while most
Japanese respondents reported their sleep problems
improving over time. Many factors may explain this
change. One simple one is age, as we know that sleep
quality decreases with age
33
. Potential differences in time
spent in bed, which is strongly influenced by the regional
culture and socioeconomic status of the population,
might explain the variation in types of sleep problems
that were reported by participants in this study from
different countries. Environmental issues, transportation
and security consideration may also have an influence on
sleep
34
. We do not have enough sociocultural data in this
study to explain why the development of a sleep disorder
differs from one country to another. Interestingly, while
most sleep problems may have changed in severity, they
rarely changed in nature, with the predominant symptom
remaining the same for most individuals.
One of the most interesting observations from this
survey is the perception that many individuals have
regarding the chronic nature of their sleeping problems.
Almost half of respondents did not consider their
symptoms to be chronic, despite having experienced
them for a considerable length of time. This suggests that
the perception of chronic status may be more linked to
the frequency of the symptom rather than its duration,
and possibly partially explains the under-reporting and
under-treatment of these symptoms.
The relevance of cultural issues with regard to the
concepts explored by the questionnaire, and also in the
observed results are very interesting. Are the differences
observed between countries only due to cultural
habits and perception, or is it possible to say that the
Japanese sleep better than people in other countries? It
is particularly interesting to observe that when patients
with insomnia are recognized in Japan, 90% are treated
with a hypnotic. One hypothesis to explain the difference
would be to imagine that sleep disorders are less frequent
and better treated in Japan. Another would be that, taking
account of cultural issues, the Japanese are less likely to
report/complain of insomnia than Western Europeans
or Americans, and are treated only if the complaints are
severe (particularly if they impact on work ability).
Zammit and colleagues have previously shown that
sleep problems impair ability to perform work and
daily activities
21
, as have several other studies
18,19
. In our
study, chi-squared analysis found a number of common
predictive factors for impairing ability to perform daily
activities across the regions. These included experiencing
several symptoms, experiencing symptoms frequently,
and experiencing problems or comorbidities related to
sleeping problems. In the USA and Western Europe,
those who had impaired daily function were more likely
to take a prescribed medication (hypnotic) or another
means of resolving sleeping problems, whereas in Japan,
individuals were more likely to take other kinds of
medications. This difference may be due to the fact that
Japanese physicians often prefer to use the terms ‘sleep-
inducing drug’, or ‘hypnotic tranquilizer’ rather than
‘hypnotic’ when prescribing benzodiazepines or newer
non-benzodiazepine hypnotics, because in Japan the
term ‘hypnotic’ is associated with the older, relatively
harmful hypnotic barbiturates.
Participants in the USA were more likely to report
a disorder attributed to their sleeping problems,
particularly fatigue or tiredness. Very few participants
considered that they did not have any disorders associated
with their sleeping problems. Stress and overwork were
commonly associated with sleeping problems across all
regions. In the USA, being overweight was a common
association (as has been recently shown by Vorona
et al.
35
), while nervousness and irritability was more
pronounced in Western Europe. Japanese respondents
were more likely to report that they did not have any
associated comorbidity compared with respondents from
Western Europe and the USA. This is possibly a function
of different cultural and societal practices across regions.
Individuals who experienced comorbidities were more
frequently treated for their sleeping problems than those
without comorbidities.
Importantly, and unsurprisingly, this study reinforces
the findings of the previous survey
27
that show that sleep
problems are under-reported and under-treated across
all regions. Extrapolation to the general population
highlights the level of under-treatment: 31.9
million
(±
0.9%), 49.1
million (±
1.3%), and 8.2
million (±
1.5%)
people with sleep problems in Western Europe, the
USA, and Japan, respectively, have never taken any steps
to resolve their sleep problems and 49.6
million (±
1.1%),
80.3
million (±
1.5%), and 17.2
million (±
2.1%) people
with sleep problems have not taken a prescription
drug for their sleeping problem in the past 12 months,
respectively. The reasons for this have yet to be clearly
established; however, previous studies have suggested
that this might be attributed to the short duration of
primary-care consultations, lack of recognition of sleep
problems as a medical concern and lack of knowledge
and understanding of available treatments
36–38
. Japanese
respondents who did consult a physician regarding their
sleep problems were considerably more likely to receive a
316 Omnibus: sleep problems in the general population © 2008 LIBRAPHARM LTD – Curr Med Res 2008; 24(1)
prescription medication than those in Western Europe or
the USA. Those who experienced several sleep symptoms,
who considered their problems to be chronic, or who
experienced comorbidities as a result of sleep problems,
were more likely to receive a drug prescription across all
regions. Interestingly, those in Japan who experienced
an improvement in their symptoms were more likely to
have a prescription medication, whereas those in Western
Europe and the USA who experienced a worsening were
more likely to have a prescription medication for their
sleep problems. This difference may be due to the time
restriction of 28 days for the prescription of hypnotics in
Western Europe which means that when sleep problems
and comorbidities improve, physicians tend to limit the
prescription.
As a result of the international scope of this project,
the study had several limitations.
Different types of interviewing technique (internet,
telephone or questionnaires via post) were used
depending on the country and may impact the results
obtained. We understand that these different techniques
of interviewing people may deeply impact the responses
of subjects and that it is a limitation of the study.
However, these different techniques were used in an
attempt to follow the cultural habits of each participating
country and to try and match as closely as possible
the usual conventions of interviewing people. Several
comparative studies have also shown that using DC
channel is low. When asking a respondent if they have
difficulties falling asleep, the answer is similar by phone,
by post, or by internet. However, if the DC channel is
not adapted to the specific culture of each country,
the risk of introducing a bias in the recruitment is high
(particularly with an elderly population).
The authors are also conscious that interviewing
people about sleep problems may substantially influence
their answer on daytime correlates and functioning. It is,
however, difficult to avoid this kind of bias in focused
epidemiological studies.
We also understand that the translation of the
questionnaire into different languages is a very difficult
issue. Local questionnaires have been validated by sleep
specialists and double-checked by the national poll
institutes on the linguistic aspect. However we did not
use the complete process of validating a questionnaire
(translation forward and translation backward, use in
pilot group…) and it is possible that this limitation had
an impact on the differences found between countries.
Another issue is excluding subjects suffering from
other sleep troubles from the survey. We are conscious
that sleep apnea and restless legs syndrome are
underdiagnosed and that people may not be conscious
that their sleep disorders may be related to them.
However this study was not based on objective measures
of sleep, and it was not possible to avoid this bias.
The results of the five European countries were
combined in this paper to aid the comprehension of the
global results. We believe, however, that it would be of
value in a future paper to show the differences between
these culturally different countries in more detail.
Conclusions
In conclusion, this survey highlights the considerable
burden of sleep problems across Europe, the USA and
Japan, with sleep maintenance of particular concern to
individuals in Western Europe and the USA and sleep
induction a particular issue in Japan. Sleep problems
continue to be under-reported and under-treated.
While Japanese individuals who consult their physician
about their sleeping problems generally receive a drug
prescription, only half of those in Western European or
the USA who consult their doctor are likely to receive a
prescription, even if they complain about deterioration
in their ability to perform daily activities. Primary
care physicians may be the most effective means of
diagnosing sleep problems in their patients and initiating
the appropriate treatment strategy; however, greater
education and provision of guidelines for primary care
physicians may be required to ensure that this occurs.
Future research focusing on the impact of educating
primary care physicians on the prevalence and severity of
chronic insomnia would be of value.
Acknowledgments
This manuscript was supported by an educational
grant from Sanofi-Aventis; editorial assistance, funded
by Sanofi-Aventis, was provided by Joseph Mole and
Matthew Weitz.
Declaration of interest: Dr Léger has served as a
consultant to Sanofi-Aventis, Lundbeck, GSK and Takeda.
Dr Poursain is a consultant for the pharmaceutical industry
(several major pharmaceutical companies) as an expert in
Market Research & Business Intelligence. Dr Neubauer
has served as a consultant to Neurocrine Biosciences,
Pfizer, Sanofi-Aventis and Takeda Pharmaceuticals. Dr
Uchiyama is a medical expert for Takeda Pharmaceuticals,
Astellas and Integrated Development Associates; and is a
consultant for Banyu Pharmaceuticals.
All authors have participated in the design and the
analysis of this study.
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CrossRef links are available in the online published version of this paper:
http://www.cmrojournal.com
Paper CMRO-3615_4, Accepted for publication: 05 November 2007
Published Online: 07 December 2007
doi:10.1185/030079908X253771
Appendix
A detailed description of the questionnaire used for this study is available as electronic supplementary data
(doi:10.1185/030079908X253825) published with the online version of this article.
