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RES E AR C H A R T I C L E Open Access
Prevalence of obstructive sleep apnea in Asian
adults: a systematic review of the literature
Aibek E Mirrakhimov
1,2*
, Talant Sooronbaev
2
and Erkin M Mirrakhimov
1,2
Abstract
Background: Obstructive sleep apnea (OSA) is a common disease, affecting approximately 2% of women and 4%
of men residing in Western communities. No systematically reviewed data are available about the prevalence of this
disease in Asia, the most heavily populated continent.
Methods: PubMed/Medline, Scopus and Google Scholar were searched for articles published from 1993 to May
2012 that reported the prevalence of OSA diagnosed via sleep monitoring and the prevalence of patients at risk for
OSA as assessed by symptomatology and/or sleep questionnaires. We have also searched abstract database of
major pulmonary and sleep scientific societies for relevant abstracts presented from 2010 to 2012. The following
inclusion criteria were used: articles published in English, age ≥ 18 years, ≥ 100 participants in studies using sleep
monitoring for the diagnosis of OSA, ≥ 300 participants in studies using questionnaires to detect patients at high
risk for OSA. Exclusion criteria: duplicate publications, studies reporting the prevalence of central sleep apnea only,
hospital based studies as well as studies assessing OSA prevalence among patients with resistant arterial
hypertension, chronic kidney disease, heart failure and in patients with concomitant neurological disease.
Results: Twenty four articles were found to meet the inclusion criteria, covering 47,957 subjects (26,042 men and
21,915 women) and four relevant abstracts were noted. OSA prevalence ranged from 3.7% to 97.3%. Male gender,
older age, a higher BMI and waist to hip ratio, greater neck circumference, arterial hypertension, smoking, snoring
and daytime sleepiness were associated with OSA. Sample size, difference between the populations studied and
the fact that some works included patients with a high pre-test probability of OSA explain the difference in
prevalence rates.
Conclusion: This systematic review highlights the lack of data regarding the prevalence of OSA in Asians. Only a
few studies provide an approximate estimate of the OSA burden in some Asian communities.
Keywords: Obstructive sleep apnea, Obstructive sleep apnea syndrome, Epidemiology, Prevalence, Asia,
Systematic review
Background
Obstructive sleep apnea (OSA) is a common medical
condition and a form of sleep disordered breathing
(SDB), which is characterized by repetitive complete
and/or partial collapses (apnea and hypopnea respect-
ively) of the upper airways. The disease is classified as
mild, moderate and severe based on the number of
apneas and/or hypopneas per hour of sleep, known as
the apnea-hypopnea index (AHI). This is assessed by
polysomnography (PSG) or other forms of sleep mo-
nitoring [1]. Obesity, aging , male sex, smoking and alco-
hol intake are the risk factors for OSA.
Subjects with OSA may complain of excessive daytime
sleepiness (EDS) or insomnia, nocturia and morning
headaches, but some patients with OSA may be asymp-
tomatic. Several clinically helpful questionnaires are
available for detecting patients at high risk for OSA such
as the Berlin Questionnaire [2] and Epworth Sleepiness
Scale (ESS) [3], but the diagnosis is made by PSG or by
home sleep monitoring, and these questionnaires are
only of ancillary use. For more general information on
* Correspondence: amirrakhimov1@gmail.com
1
Kyrgyz State Medical Academy named after I.K. Akhunbaev, Akhunbaev
Street 92, Bishkek 720020, Kyrgyzstan
2
National Centre of Cardiology and Internal Medicine named after М.
Mirrakhimov, T.Moldo Street 3, Bishkek 720040, Kyrgyzstan
© 2013 Mirrakhimov et al.; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the
Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use,
distribution, and reproduction in any medium, provided the original work is properly cited.
Mirrakhimov et al. BMC Pulmonary Medicine 2013, 13:10
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OSA, please refer to a well- written review article on this
topic [4].
Asia is the most heavily popula ted continent, with
some groups living in an underdeveloped environment.
To date there are no published scientific reports on the
general prevalence of OSA in Asia.
The rationale for this manuscript is to systemize the
current data on the prevalence of OSA and patients at
risk for OSA obtained from the Asian population and to
highlight potential shortcomings, which should be
addressed in future epidemio logic works.
Methods
Search strategy and selection criteria
The systematic review was performe d according to the
key tenets of the PRISMA guidance for systematic
reviews [5]. PubMed/Medline, Scopus, Google Scholar
databases were searched for articles published from 1993
to September 2012 that reported the prevalence of OSA
diagnosed via instrumental sleep monitoring and full
PSG and the prevalence of patients at risk for OSA
among Asians as assessed by symptomatology (snoring,
daytime sleepiness etc.) and/or questionnaires .
Scientific abstracts presented on the last three scien-
tific meetings (2010– 2012) of American Academy of
Sleep Medicine, American Thoracic Society, American
College of Chest Physicians, European Respiratory Soci-
ety, Asian Pacific Society of Respirology were searched.
The data from the relevant abstracts will be discussed in
the discussion only, due to limited amount of informa-
tion provided in them.
The search terms were: obstructive sleep apnea, ob-
structive sleep apnea syndrome, sleep disordered breath-
ing, prevalence, risk factors for obstructive sleep apnea,
Asia and the names of Asian countries (including Israel
and Turkey) as well as a combination of the se. Reference
lists of relevant articles were checked to find potentially
relevant publications that may have been overlooked by
the ele ctronic search.
The articles identified, were screened by title and ab-
stract, and selected for full text review if they met the
following inclusion criteria: studies performed in Asia ,
documenting OSA prevalence and/or prevalence of
patients at risk for OSA, articles in English, age ≥ 18
years, ≥ 100 participants in studies using PSG or other
forms of instrumental sleep monitoring for the diagnosis
of OSA, ≥ 300 participants in studies not using PSG for
OSA detection. Even, if the study’s goal was not to assess
the epidemiology of OSA, but the prevalence was
examined and included in the results, such studies were
eligible for inclusion.
Specific exclusion criteria: duplicate publications, stud-
ies reporting the prevalence of central sleep apnea only,
hospital based studies as well as studies assessing OSA
prevalence among patients with resistant arterial hyper-
tension, chronic kidney disease, heart failure and stroke/
neurological disease, since the prevalence of OSA is
much higher in these groups than in the general popula -
tion [6-8].
Outcomes studied
The outcomes were the prevalence of OSA diagnosed
by full PSG and other types of instrumental sleep
monitoring. Another task was to study the prevalence of
patients at risk for OSA as assessed by symptomatology
and questionnaire use.
Data extraction and quality assessment
General data extraction included the information on the
publication dates, methodology of the study, number of
individuals enrolled and their characteristics as well as
definition of OSA and its measurement (sym ptomatol-
ogy/questionnaire vs. instrumental sleep monitoring).
The quality assessment tool was modified from the
checklist recommended by the centre for
Reviews and Dissemination, York, United Kingdom and
included [9]: clear goals and objectives of the study, clear
and appropriate methods, risk of bias in selection, risk
of bias in study outcomes (0 points for obvious bia s risk
present, 1point if no apparent bias risk present), diagno-
sis of OSA (0 points for non-instrumental sleep study, 1
point for instrumental sleep monitoring other than PSG,
2 points for PSG), discussion of the limitations, funding
information and conflicts of interest. Since, all suitable
studies were cros s-sectional works; therefore, prospect-
ive methodology was not scored. The maximal score for
an individual study in terms of quality was 8 points. The
maximal quality score for studies using questionnai res
was 6, given that they did not use instrumental sleep
monitoring.
Results
A total 732 articles were found on the prevalence of
OSA in Asia and the prevalence of patients at risk for
OSA based on questionnaire and/or symptom assess-
ment. Of these 676 articles were excluded after abstract
screening for the following reasons: not focused on the
studied outcomes (n-416), studies in pediatric popula-
tion (n-90), reviews, comments/editorials (n-67), articles
not published in English (n-39), small sample (n-33),
studies performed in patients with certain comorbidities
(n-20), studies performed outside Asia (n-9), animal
studies (n-7).
Fifty one full text articles were evaluated, with 28
articles excluded for the following reasons: hospital-
based studies (n-18), not focused on studied outcomes
(n-7), duplicate publications (n-2). Twenty four arti-
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cles covering 47,957 patients (26,042 men and 21,915
women) were eligible based on the aforeme ntioned cri-
teria. Many studies were excluded for more than one
reason.
Below, we review the data on the prevalence of
patients at risk for OSA first, and then the data on the
prevalence of OSA based on the instrumental assess-
ment. The diagram of the literature search is shown in
Figure 1.
Community studies using sleep questionnaires
Ten manuscripts were community studies. These inclu-ded
32,508 participants (17,580 women and 14,928 men): two
studies from Turkey (n-6,117) [10,11], two studies from
Taiwan/China (n-5,263) [12,13], two studies from Iran
(n-4,056) [14,15], one study each from Japan (n-8,483) [16],
Thailand (n-4,680) [17], Singapore (n-2,298) [18] and
Malaysia (n-1,611) [18]. A summary of the studies is
presented in Table 1.
Included studies used the Berlin questionnaire, Sleep
and Health questionnaire, ESS and modified sleep
questionnaires. The prevalence of patients at high risk
for OSA ranged from 4.98% [14] to 27.3% [15], both
from Iranian studies. This difference could be explained
by the fact that the study with a lower prevalence [14]
included a higher number of women and a much
younger population, as well as a larger sample.
Other studies reported the prevalence of snoring,
witnessed apnea, EDS and insomnia. The lowest snoring
prevalence of 4.6% was reported in Thailand [17] and
the highest pre valence of 59.1% was in Taiwan [13]. The
study from Thailand [17] included a much higher num-
ber of women and the population was younger than in
the study from Taiwan/China [13]. The lowest preva-
lence of witnessed apneas was 2.6% in Taiwan [13], and
the highest was 15.2% in Malaysia [19]. Symptoms of
EDS ranged from 3.85% [11] to 24% [10], both in
Turkish studies. The difference in EDS prevalence could
be explained by the different sample sizes and popu-
lations studied.
Male gender, older age, greater BMI and neck circum-
ference, smoking, alcohol intake, sedative use, health
illiteracy and Indian and Chinese ethnicity were related
to a high risk for OSA.
As already mentioned the questionnaires have some
limitations and are only suitable for the detection of
patients with a high pretest probability of OSA. The
included studies were of different methodological qual-
ity, and some did not report such valuable information
as BMI. Some studies reported data only in terms of
symptomatology. Despite having, a good sensitivity for
OSA, the specificity and positive predictive value for the
disease are much lower than desired, and these factors
interfere with the translation of the results of OSA
questionnaires into real life scenario. The quality scores
of these articles are presented in Table 1.
Community studies with instrumental sleep monitoring
and/or full PSG assessment
Fourteen studies were community based studies using
instrumental sleep monitoring and/or full PSG including
15,449 patients (11,114 men and 4,335 women). There
were five Chinese studies (n-6,447): three from Hong-
Kong (n-3,145) [20-22], two studies from mainland
China (3,302) [23,24]; four Japanese studies (n-3,475)
[25-28], two Indian studies (n-4,665) [29,30], and one
Figure 1 Flow chart of selected studies.
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Table 1 Summary of the community studies without PSG assessment
Study Country Study design Population studied Prevalence of patients
at high risk for OSA
Risk factors Quality assessment
score
Ozdemir et al.
[10]; 2005
Turkey Cross-Sectional study
using Sleep and
Health questionnaire
n-5,339 females-50.6% mean age- 38.4 years
BMI-no data provided
40.3% had insomnia, 37% were snorers, 24% had
EDS and 6.4% had episodes of witnessed apneas
None reported. 2 points: single area
study, no discussion of
the potential limitations
and no funding
information.
Kart et al. [11];
2010
Turkey Cross-Sectional study
using adapted
version of the Berlin
questionnaire
n-778 males-100% coal miners- 54.3% mean
age-43.3 years for coal miners and 44.3
years for controls mean BMI-27.2 kg/m
2
and
26.1 kg/m
2
for coal miners and controls
respectively
40.7% of all included participants had snoring,
4.37% had witnessed apneas and 3.85% had
EDS.
None reported. 3 points: single area
study, no funding
information.
Liu et al. [12];
2004
Taiwan/
China
Cross-Sectional study
using modified
questionnaire via
telephone
interviewing
n-1,252 females-51.6% mean age 38.6 years
BMI-data no provided
46.8% were snorers Male gender and age
range of 40–59 years
2 points: single area
study, no discussion of
the potential limitations
and no funding
information.
Chuang et al.
[13]; 2008
Taiwan/
China
Cross-sectional study
using modified
questionnaire via
telephone
interviewing
n-4,011 females-59.2% age-15-30-15.8%;
age-30-50-36.1%; age > 50-48.1% mean BMI-
23,15 kg/m
2
Overall presence of snoring was 59.1%: 60.8% for
males and 42.5% for females Snoring in females
<50 years was present among 37.1% vs. 49.1%
in females > 50 years. Snoring in males < 50
years was present among 57.9% vs. 63% in
males > 50 years. Overall presence of witnessed
apnea was 2.6%: 3.4% for males and 1.9% for
females. Witnessed apnea in males < 50 years
was present among 2.3% vs. 5.3% in males > 50
years. Witnessed apnea in females < 50 years
was present among 1.4% vs. 2.8% in females >
50 years
Male gender and age >
50 years
4 points: no funding
information provided.
Amra et al.
[14]; 2011
Iran Cross-Sectional study
using Berlin
questionnaire
n-3,529 females-53.3% mean age-40.47 and
38.61 years for males and females
respectively mean BMI-25.05 and 26.39 kg/
m
2
for males and females respectively
4.98% of participants were at high risk for OSA
(102 females and 74 males)
Obesity, older age and
illiteracy
3 points: single area
study, no discussion of
the potential
limitations.
Khazaie et al.
[15]; 2011
Iran Cross-Sectional study
using Berlin
questionnaire
n-527 males-77.9% mean age-48.6 years
mean BMI-25.1 kg/m
2
27.3% were at high risk for OSA. 9.67% reported
witnessed apneas
Illiteracy 3 points: single area
study, no funding
information.
Nagayoshi
et al. [16];
2011
Japan Cross-Sectional study
using modified
questionnaire
n-8,483 females-63% mean age-59.8 years
mean BMI- 23.4 kg/m
2
24% of males and 10% of females had snoring. Alcohol intake and
possibly smoking
6 points
Suwanprathes
et al. [17];
2010
Thailand Cross-Sectional study
using modified
questionnaire
n-4,680 females-54% median age- 34 years
mean BMI- 26.03 kg/m
2
for patients with
sleep complaints and 22.77 kg/m
2
for others
4.6% of general sample had snoring and EDS.
5.3% of males and 3.5 of females had snoring.
Male gender, greater
waist circumference and
BMI
4 points: single area
study, no discussion of
the potential
limitations.
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Table 1 Summary of the community studies without PSG assessment (Continued)
Khoo et al.
[18]; 2004
Singapore Cross-Sectional study
using modified
questionnaire
n-2,298 (35%-Chinese, Malay-33.7% and
Indians-31.3%) females-52% age 20–59
years-85.4% and age > 60 years-14.6%
BMI ≥ 30 kg/m
2
-6.2%
6.8% of the total population complained
of snoring
Male gender, age > 60
years, Indian ethnicity,
family history, obesity,
neck circumference >
40 cm and smoking
6 points
Kamil et al.
[19]; 2007
Malaysia Cross-Sectional study
using modified
questionnaire and
Epworth Sleepiness
Scale for EDS
n-1,611 (47.1%-Malay, 36.6%-Chinese, 11.3%-
Indian and 5%-others) males-52.9% mean
age-49 years BMI-data not provided
47.3% had snoring, 15.2% had witnessed apneas
and 14.8% had EDS
Older age, Chinese/
Indian origin vs. Malay,
smoking (both past and
current), obesity and
sedative use
4 points: no discussion
of the potential
limitations and no
funding information.
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Table 2 Summary of the community studies with instrumental sleep and/or full PSG assessment
Study Country Study design Population studied OSA/SDB prevalence Risk factors and
associated states
Quality assessment
score
Ip et al. [20];
2001
China/
Hong-
Kong
Cross-Sectional study using sleep
questionnaire and PSG
n-784 (153 underwent PSG)
Males-100% Mean age-41.2 years
Mean BMI-23.9 kg/m
2
23% had snoring. 41.8% were diagnosed
with OSA by PSG. Estimated OSA and
OSAS prevalence was 8.8% and 4.1%
Older age, higher
BMI, snoring and
time taken to fall
asleep
6 points: single area
study, no funding
information.
Ip et al. [21];
2004
China/
Hong-
Kong
Cross-Sectional study using sleep
questionnaire and PSG
n-884 (105 underwent PSG) Females-
100% Mean age-41.6 years Mean
BMI-22.4 kg/m
2
15% had snoring. AHI ≥ 5, AHI ≥ 10 and
AHI ≥ 15 were present among 30%, 15%
and 10% respectively. Estimated
prevalence of OSA and OSAS was 3.7%
and 2.1% respectively
Older age and
higher BMI
5 points: single area
study, no discussion of
potential limitations
and no funding
information.
Hui et al. [22];
2006
China/
Hong-
Kong
Cross-Sectional study using sleep
questionnaire, 4 channel home sleep
monitoring and PSG
n-1,477 (211 undergone 4 channel
home sleep study and 25 have been
assessed by PSG) Males-65.74% Mean
age-45.3 years Mean BMI- 24.9 kg/m
2
EDS was present in 60.9%, falling asleep
in 24%, snoring in 23.9% and witnessed
apnea in 3.7%. RDI ≥ 5 was present in
83.9% and RDI ≥ 15 was present in
17.5%. It was estimated that OSA and
OSAS was present in 8.4% and 4.4%
respectively
Higher BMI, neck
circumference and
snoring
6 points: single area
study, no funding
information.
He et al. [23];
2010
China Cross-Sectional study using PSG n-2,297 Males-86.24% Mean age-46
years Mean BMI- 27.64 kg/m
2
88.81% were diagnosed with OSA and
51.28% were diagnosed with severe OSA
Systolic and diastolic
blood pressure
6 points: no discussion
of the potential
limitations and no
funding information.
Chen et al.
[24]; 2011
China Cross-Sectional study using PSG n-1,035 Males-83.67% Mean age-45
years Mean BMI- 26.2 kg/m
2
in mild
OSAS, 27.5 kg/m
2
for moderate and
28.8 kg/m
2
for severe OSAS
75.9% had OSAS and 37.7% had
AHI > 40.
ESS score correlated
with ODI, AHI and
BMI. ODI was
associated with ESS
score.
6 points: Single area
study and no discussion
of the potential
limitations.
Tanigawa
et al. [25];
2004
Japan Cross-Sectional study using pulse
oximetry monitoring
n-1,424 Males-100% mean age-58.6
years Mean BMI-24 kg/m
2
31.46% and 9% had ODI of 5–15 and
ODI > 15 respectively
Arterial hypertension,
BMI, smoking and
older age
4 points: single area
study, PSG was not
used, no discussion of
the potential limitations
and no funding
information.
Cui et al. [26];
2006
Japan Cross-Sectional study using pulse
oximetry monitoring
n-1,313 Males-96% Mean age- for 3%
ODI of 5–14 was 47 years and 47.3
years for 3% ODI > 15Mean BMI- 3%
ODI of 5–14 was 25.6 kg/m
2
and 28.5
kg/m
2
for 3% ODI > 15
Subjects aged 40–69 have SDB
prevalence of 8.5% compared to 4%
among aged 20-39
age ≥ 40 years,
higher BMI, ESS > 11
and arterial
hypertension
6 points: PSG was not
used, no funding
information.
Okabayashi
et al. [27];
2007
Japan Cross-Sectional study using home
pulse oximetry and then PSG study
among Japanese workers
n-368 underwent home pulse oximetry
and 153 were screened with PSG Males-
100% Mean age-45.7 years Mean
BMI-25.8 kg/m
2
313 patients out of 368 (85%) had ODI ≥
5 events. 149 out of 153 (97.3%) had
OSA
7 points: no funding
information.
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Table 2 Summary of the community studies with instrumental sleep and/or full PSG assessment (Continued)
Asaoka et al.
[28]; 2010
Japan Cross-Sectional study using 3 channel
home sleep monitoring in patients
with positive ESS and/or snoring,
witnessed apneas, BMI ≥ 25 kg/m
2
and concomitant arterial
hypertension
n-370 undergone home sleep study;
129 participants undergone PSG study
Males-100% Mean age-44.5 years Mean
BMI-24.3 kg/m
2
OSA was present among 3.7% 5 points: single area
study, PSG was not
used, no funding
information
Sharma et al.
[29]; 2006
India Cross-Sectional study using sleep
questionnaire and PSG
n-2,150 Males-52.8% Mean age-43.9
years for snorers Mean BMI- 27 kg/m
2
151 subjects (77 snorers and 74
nonsnorers) undergone PSG
25.16% subjects were found to have OSA
and 7.28% subjects were found to have
OSAS (among who underwent PSG). It
was estimated that 13.74% and 3.57% of
the population should have OSA and
OSAS respectively
Male gender, older
age, snoring, higher
BMI and greater
waist to hip ratio
6 points: single area
study, no funding
information.
Reddy et al.
[30]; 2009
India Cross-Sectional study using sleep
questionnaire and PSG
n-2,505 Males-50.4% Mean age-41 years
Mean BMI-24.3 kg/m
2
360 subjects
(287 snorers and 73 nonsnorers)
undergone PSG
26.94% subjects had OSA and 12.2%
subjects had OSAS (among who
underwent PSG).
Male gender, BMI ≥
25 kg/m
2
and
abdominal obesity
7 points: single area
strudy.
Kim et al.
[31]; 2004
Korea Cross-Sectional study using home
sleep study or PSG
n- 457 Males- 67.6% Mean age-49.1
years for males with snoring and 54.3
years for females with snoring Mean
BMI-26.5 kg/m
2
for males with snoring
and 26.6 kg/m
2
for females with
snoring
OSA and was found in 42% men and
20% women and OSAS was present in
4.5% men and 3.2% women
Male gender, higher
BMI and
hypertension
7 points: single area
study.
Yusoff et al.
[32]; 2010
Malaysia Cross-Sectional study using PSG n-279 Males-100% Mean age-43.8 years
Mean BMI- 29.4 kg/m
2
for patients
with OSA
44.3% had AHI ≥ 5 and 6.6% had
xAHI ≥ 30.
Older age, greater
BMI and neck
circumference,
snoring and
hypertension
7 points: no discussion
of the potential
limitations.
Puvanendran
et al. [33];
1999
Singapore Cross-Sectional study using PSG n-106 male: female ratio 9:1 No data on
mean age and mean BMI are provided
87.5% had OSA and 72% had OSAS. It
was calculated that 15.7% of the
Singaporean population may have OSA.
6 points: no discussion
of the potential
limitations and no
funding information.
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each from Korea (n-5,020) [31], Malaysia (n-279) [32]
and Singapore (n-106) [33]. The summary of the studies
is presented in Table 2.
Six studies used PSG [20,21,23,24,32,33], 2 studies used
PSG and a sleep questionnaire [29,30], one study used a
sleep questionnaire, home sleep monitoring and PSG
[22], one study used home sleep study and PSG [31], one
study used overnight pulse oximetry monitoring and PSG
[27], one study used three channel home sleep monitoring
[28] and two studies used overnight pulse oximetry
[25,26]. The smallest sample consisted of 106 participants
(Singaporean study) [33], and the largest consisted of
2,505 participants (Indian study) [30]. Men were predom-
inant studied group in most studies, whereas one study
enrolled exclusively women [21].
The mean age of participants ranged from 41.2 years
in the stud y from Hong-Kong/China [20] to 58.6 years
in the Japanese study [25]. The mean BMI varied from
22.4 kg/m
2
in the study from Hong-Kong/China [21] to
29.4 kg/m
2
in the Malaysian study [32]. The study from
Singapore did not report data on either mean age or
mean BMI [33].
OSA prevalence ranged from 3.7% one Japanese study
[28] to 97.3% in another study from Japan [27]. This
huge differ ence may be attributed to the different
populations studied with a greater BMI and older age in
the latter study. Another potential explanation is that
the patients that underwent PSG, in the study by
Okabayshi et al. [27] had a remarkably high pre-test
probability of OSA, since they had been tested via home
pulse oximetry.
Some studies reported the prevalence of OSA with
daytime symptoms, which ranged from 3.2% in women
and 4.5% in men in the Korean study [31] to 72% in the
study from Singapore [33]. However, the difference in
the sample size should be kept in mind, along with the
fact that the Singaporean study did not provide data on
the mean age or mean BMI. Furthermore, it was impos-
sible to extract the original article, since the journal in
which it was published no longer exists.
Some studies reported the estimated OSA/OSAS
prevalence [ 20-22,29], which ranged from 3.7%/2.1% in
the study performed by Hong-Kong researchers in
women [20] to 13.74%/3.57% in the Indian study [29].
The Indian study [29] had a predominantly male sample,
and the population was heavier and older than in the
study from Hong-Kong [20], which recruited exclusively
women and these factors can help explain the difference
in estimated disease burden.
Male gender, older age, greater BMI, neck circumfer-
ence and waist to hip ratio, increased blood pressure,
smoking, snoring, time taken to fall asleep and a higher
ESS score were associated with OSA in the aforemen-
tioned studies.
Since the studies were of different methodological
quality, tested differ ent populations, and used various
types of sleep monitoring to assess OSA and since many
countries lack any epidemiologic data, it is particularly
difficult to extrapolate the data to the global disease
prevalence in Asia. However, the studies performed
by Ip et al. [20,21], Hui et al. [23] and Reddy et al.
[30] are likely to be representative of their respective
populations. Based on these results it is likely that in
Hong-Kong study the average prevalence of OSA is
around 7%, and that of OSA with daytime symptoms is
around 3.5%, whereas in India the prevalence is 13.74%
for OSA and 3.57% for OSA with daytime symptoms.
Discussion
OSA is a particularly common and underrecognized med-
ical disorder. It is associated with increased morbidity and
mortality from cardiovascular causes, and traumatic
accidents due to EDS. OSAS, which is characterized by
abnormal AHI and symptoms of EDS, is present in 2% of
women and 4% of men living in Western communities.
The Asian continent is heavily populated, and many
groups live in an underdeveloped environment. These
factors pose some difficulties in assessing the disease
burden in this area. As expected most studies came from
developed countries such as Japan, China, Singapore,
Turkey and others. Interestingly, no epidemiologic stud-
ies have been conducted in Israel, despite the many
works performed there in the area of OSA pathophys-
iology.
The retrieved studies were divided into two main
groups: studies using sleep questionnaires and those
studies using various sleep studies inc luding PSG. Com-
munity studies are more likely to portray epidemiology
with better accuracy than single center hospital studies.
Second, hospital studies usually enroll patient s with a
high pre-test probability of diagnosis, whic h is true for
studies using questionnaires/symptomatology as well as
PSG studies. Given the latter concern, hospital based
studies were excluded from this review.
It is well known that sleep questionnaires despite
being useful in assessing risk for OSA, are not inter-
changeable with instrumental sleep studies and cannot
quantify the se verity of disease. Thus, the prevalence of
people at high risk for OSA based on questionnaires
cannot be simply converted into the prevalence of OSA.
Another flaw is that questionnaires such as the ESS can-
not rule out other sleep disorders; in fact this scale was
primarily invented to detect EDS [3], and not OSA or
patients at high risk for OSA.
Ten community studies that used sleep questionnaires
and assessed OSA associated symptoms were found.
Most of these studies used modified versions of sleep
questionnaires with questions regarding snoring, noctur-
Mirrakhimov et al. BMC Pulmonary Medicine 2013, 13:10 Page 8 of 10
http://www.biomedcentral.com/1471-2466/13/10
nal apneas, EDS, daytime fatigue etc. The smallest sample
was 527 in the Iranian study [15] and the largest sample
was 8,483 in the Japanese study [16]. The reported preva-
lence of risk for OSA prevalence ranged from 4.98% to
27.3%, both in the Iranian studies [14,15]. Male gender,
older age, higher BMI, greater waist to hip ratio and neck
circumference, illiteracy, alcohol intake and smoking were
associated with at high risk for OSA.
Fourteen community studies using sleep monitoring
were found. Some of these were two phase studies that
used a sleep questionnaire and sleep monitoring. The
smallest sample was 106 in the study from Singapore
[33] and the largest sample was 5,020 in the Korean
study [31]. The prevalence of OSA ranged from 3.7% in
the Japanese study [28] to 88.81% in the Chinese study
[23]. Male gender, older age, a higher BMI and waist to
hip ratio, greater neck circumference, arterial hyperten-
sion, smoking, snoring and a higher ESS score were
related to OSA. The striking difference in prevalence
can be attributed to variations in sample size and differ-
ent popula tions studied, since some predominantly
assessed patients with OSA related symptoms such as
snoring, witnessed apnea etc.
Since the studies were of different methodological quality,
tested different populations, used various types of sleep
monitoring to assess OSA and many countries l ack any
epidemiologic data, it is particularly difficult to extrapolate
the data to the global OSA/OSAS prevalence in Asia. How-
ever, the studies performed by Ip et al. [20,21], Hui et al.
[22] and Reddy et al. [30] are likely to be representative of
their studied populations. Based on these results it is likely
that averag e prevalence of OSA is around 7%, and OSAS
prevalence is around 3.5% in Hong- Kong and 13.74% for
OSA and 3.57% for OSAS in India.
Several abstracts from the databases mentioned in the
“Search strategy and selection criteria” were found rele-
vant for discussion. We used the same sample size cut off
for abstract reports as for regular articles. However, it is
necessary to note that it is difficult to analyze the abstracts
in a thorough fashion due to limited word count. Pablo
et al. screened 458 Philippine medical students with Berlin
questionnaire and ESS [34]. These researchers showed
that approximately 75.9% of studied participants had
symptoms of EDS, but no data was provided on the Berlin
questionnaire scores. It is essential to mention that their
sample of medical students may not represent a general
Philippine population. Liu et al. interviewed 666 patients
undergoing anesthesia with Berlin questionnaire at West
China Hospital of Sichuan University, China [35]. These
investigators found that 11.7% were found to be at high
risk for OSA. The individuals at high risk for OSA had a
greater prevalence of high blood pressure, snoring and
EDS. Ardic et al. screened 5,021 adults (2,598 women)
with Berlin questionnaire in Ankara, Turkey [36], abstract
0418. These researchers showed that 13.7% of the screened
population was at high risk for OSA. Li et al. retrospectively
analyzed the PSG data of 2,335 individuals (1,960 men)
who were suspected to have OSA [36], abstract 0466 in
West China Hospital of Sichuan University, China. They
showed a greater prevalence of OSA among men. Since,
the above study was assessing the PSG of the patients who
likely were initially at high risk for OSA, it is impossible
to extrapolate this data to general Chinese population.
Chang et al. studied 284 subjects with snoring problems
with home sleep monitoring [36], abstract 0467. These
investigators found that 61.3% of individuals had SDB.
Since, these individuals had complaints of snoring before
the actual sleep testing; they were at high risk for OSA,
which make this finding inapplicable to general Chinese
population.
Overall, based on the present stud ies it is difficult to
estimate the potential prevalence of OSA/OSAS in the
general population in these countries , because of the
heterogeneity of the subjects and methods used to assess
patients at risk and different types of sleep monitoring
devices used.
Moreover, there are still no prevalence data for most
Asian countries, including Bangladesh, Mongolia, Syria,
former Soviet Union countries located in Asia and
others. Future studies should recruit patients, who are
generally considered to be at low risk for OSA to give a
better understanding of the OSA burden on the Asian
continent. This will give a better insight into the preva-
lence of OSA in the general Asian population. Therefore,
more studies are needed to provide a better knowledge
on the OSA burden in the Asian continent.
Limitations
This systematic review has some potential limitations:
first, only articles written in the English language were
included. Therefore, some relevant studies may have
been missed. Another potentia l drawback could arise
from be due to limitations of the search engines used,
such as PubMed/Medline, Scopus, Google Scholar and
abstracts of the American Thoracic Society, American
College of Chest Physicians, American Academy of Sleep
Medicine, European Respiratory Society and Asian
Pacific Society of Respirology.
Conclusion
Many published studies assessed people with high pre-
test probability of OSA; thus their results may overesti-
mate the true burden of disease. Therefore, more studies
are needed to improve our knowledge on the OSA bur-
den in Asia.
Abbreviations
AHI: Apnea-hypopnea index; BMI: Body mass index; EDS: Excessive daytime
sleepiness; ESS: Epworth sleepiness scale; OSA: Obstructive sleep apnea;
Mirrakhimov et al. BMC Pulmonary Medicine 2013, 13:10 Page 9 of 10
http://www.biomedcentral.com/1471-2466/13/10
OSAS: Obstructive sleep apnea syndrome; PSG: Polysomnography; SDB: Sleep
disordered breathing.
Competing interest
The authors declared that they have no competing interest.
Authors’ contribution
All authors read and approved the final manuscript.
Received: 11 June 2012 Accepted: 21 February 2013
Published: 23 February 2013
References
1. Sleep-related breathing disorders in adults: recommendations for
syndrome definition and measurement techniques in clinical research.
The report of an American Academy of Sleep Medicine Task force. Sleep
1999, 22:667–689.
2. Netzer NC, Stoohs RA, Netzer CM, Clark K, Strohl KP: Using the Berlin
Questionnaire to identify patients at risk for the sleep apnea syndrome.
Ann Intern Med 1999, 131:485–491.
3. Johns MW: A new method for measuring daytime sleepiness: the
Epworth sleepiness scale. Sleep 1991, 14:540 – 545.
4. Eastwood PR, Malhotra A, Palmer LJ, Kezirian EJ, Horner RL, Ip MS,
Thurnheer R, Antic NA, Hillman DR: Obstructive Sleep Apnoea: From
pathogenesis to treatment: Current controversies and future directions.
Respirology 2010, 15:587–595.
5. Moher D, Liberati A, Tetzlaff J, Altman DG: Preferred reporting items for
systematic reviews and meta-analyses: the PRISMA statement. PLoS Med
2009, 6(7):e1000097.
6. Dudenbostel T, Calhoun DA: Resistant hypertension, obstructive sleep
apnoea and aldosterone. J Hum Hypertens 2012, 26:281–287.
7. Kasai T, Bradley TD: Obstructive sleep apnea and heart failure:
pathophysiologic and therapeutic implications. J Am Coll Cardiol 2011,
57:119–127.
8. Mirrakhimov AE: Obstructive sleep apnea and kidney disease: is there any
direct link? Sleep Breath. 2011. [Epub ahead of print]. PMID: 22170216.
9. Centre for Reviews and Dissemination. Systematic reviews: CRD’s guidance
for undertaking reviews in health care: Centre for Reviews and Dissemination,
University of York. 2008. http://www.york.ac.uk/inst/crd/pdf/Systematic_
Reviews.pdf.
10. Ozdemir L, Akkurt I, Sümer H, Cetinkaya S, Gönlügür U, Ozşahin SL, Nur N,
Doğan O: The prevalence of sleep related disorders in Sivas. Turkey.
Tuberk Toraks. 2005, 53:20–27.
11. Kart L, Dutkun Y, Altın R, Ornek T, Kıran S: Prevalence of major obstructive
sleep apnea syndrome symptoms in coal miners and healthy adults.
Tuberk Toraks 2010, 58:261–267.
12. Liu SA, Liu CY:
Prevalence of snoring in Taichung area: an
epidemiological study. J Chin Med Assoc 2004, 67:32–36.
13. Chuang LP, Hsu SC, Lin SW, Ko WS, Chen NH, Tsai YH: Prevalence of
snoring and witnessed apnea in Taiwanese adults. Chang Gung Med J
2008, 31:175–181.
14. Amra B, Farajzadegan Z, Golshan M, Fietze I, Penzel T: Prevalence of sleep
apnea-related symptoms in a Persian population. Sleep Breath 2011,
15:425–429.
15. Khazaie H, Najafi F, Rezaie L, Tahmasian M, Sepehry AA, Herth FJ:
Prevalence of symptoms and risk of obstructive sleep apnea syndrome
in the general population. Arch Iran Med 2011, 14:335–338.
16. Nagayoshi M, Yamagishi K, Tanigawa T, Sakurai S, Kitamura A, Kiyama M,
Imano H, Ohira T, Sato S, Sankai T, Iso H: Risk factors for snoring among
Japanese men and women: a community-based cross-sectional study.
Sleep Breath 2011, 15:63–69.
17. Suwanprathes P, Won C, Komoltri C, Nana A, Kotchabhakdi N, Guilleminault
C: Epidemiology of sleep-related complaints associated with sleep-
disordered breathing in Bangkok. Thailand. Sleep Med. 2010, 11:1025 –1030.
18. Khoo SM, Tan WC, Ng TP, Ho CH: Risk factors associated with habitual
snoring and sleep-disordered breathing in a multi-ethnic Asian
population: a population-based study. Respir Med 2004, 98:557–566.
19. Kamil MA, Teng CL, Hassan SA: Snoring and breathing pauses during
sleep in the Malaysian population. Respirology 2007, 12:375–380.
20. Ip MS, Lam B, Lauder IJ, Tsang KW, Chung KF, Mok YW, Lam WK: A
community study of sleep-disordered breathing in middle-aged Chinese
men in Hong Kong. Chest 2001, 119:62–69.
21. Ip MS, Lam B, Tang LC, Lauder IJ, Ip TY, Lam WK: A community study of
sleep-disordered breathing in middle-aged Chinese women in Hong
Kong: prevalence and gender differences. Chest 2004, 125:127–134.
22. Hui DS, Ko FW, Chan JK, To KW, Fok JP, Ngai JC, Chan MC, Tung A, Chan
DP, Ho CW, Lai CK: Sleep-disordered breathing and continuous positive
airway pressure compliance in a group of commercial bus drivers in
Hong Kong. Respirology 2006, 11:
723
–730.
23. He QY, Feng J, Zhang XL, Liang ZA, Huang SG, Kang J, Wang GF, Zhang LQ,
Ma LJ, Wang B, Lin QC, Zhang JN, Liu HG, Luo YM, Liu JH, Wang S, Xiao GH,
Lu G, Zhang J, Feng XW, Chen BY: Relationship of daytime blood pressure
and severity of obstructive sleep apnea among Chinese: a multi-center
investigation in China. Chin Med J (Engl) 2010, 123:18–22.
24. Chen R, Xiong KP, Lian YX, Huang JY, Zhao MY, Li JX, Liu CF: Daytime
sleepiness and its determining factors in Chinese obstructive sleep
apnea patients. Sleep Breath 2011, 15:129–135.
25. Tanigawa T, Tachibana N, Yamagishi K, Muraki I, Kudo M, Ohira T, Kitamura
A, Sato S, Shimamoto T, Iso H: Relationship between sleep-disordered
breathing and blood pressure levels in community-based samples of
Japanese men. Hypertens Res 2004, 27:479–484.
26. Cui R, Tanigawa T, Sakurai S, Yamagishi K, Iso H: Relationships between
sleep-disordered breathing and blood pressure and excessive daytime
sleepiness among truck drivers. Hypertens Res 2006, 29:605–610.
27. Okabayashi K, Kasahara E, Uchiyama H, Yokota K, Togashi Y, Kono C,
Yamada Y, Amano H, Yamaguchi T, Kawamoto T, Fujihara H, Ueta Y:
Obstructive sleep apnea-hypopnea syndrome patients with overweight
and hypertension in a Japanese workplace. J Occup Health 2007,
49:117–124.
28. Asaoka S, Namba K, Tsuiki S, Komada Y, Inoue Y: Excessive daytime
sleepiness among Japanese public transportation drivers engaged in
shiftwork. J Occup Environ Med 2010, 52:813–818.
29. Sharma SK, Kumpawat S, Banga A, Goel A: Prevalence and risk factors of
obstructive sleep apnea syndrome in a population of Delhi. India. Chest.
2006, 130:149–156.
30. Reddy EV, Kadhiravan T, Mishra HK, Sreenivas V, Handa KK, Sinha S, Sharma
SK: Prevalence and risk factors of obstructive sleep apnea among
middle-aged urban Indians: a community-based study. Sleep Med 2009,
10:913–918.
31. Kim J, In K, Kim J, You S, Kang K, Shim J, Lee S, Lee J, Lee S, Park C, Shin C:
Prevalence of sleep-disordered breathing in middle-aged Korean men
and women. Am J Respir Crit Care Med 2004, 170:1108–1113.
32. Yusoff MF, Baki MM, Mohamed N, Mohamed AS, Yunus MR, Ami M, Othman I,
Ishak AI: Obstructive sleep apnea among express bus drivers in Malaysia:
important indicators for screening. Traffic Inj Prev 2010, 11:594–599.
33. Puvanendran K, Goh KL: From snoring to sleep apnea in a Singapore
population.
Sleep Res Online 1999, 2:11–14.
34. Respirology. 2010, 15(Suppl. 2):55–109. abstract PD 13–04.
35. J Sleep Res 2010, 2010. Abstract Supplement. Abstract 0375.
36. J Sleep Res 2012, 35. Abstract Supplement.
doi:10.1186/1471-2466-13-10
Cite this article as: Mirrakhimov et al.: Prevalence of obstructive sleep
apnea in Asian adults: a systematic review of the literat ure. BMC
Pulmonary Medicine 2013 13:10.
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http://www.biomedcentral.com/1471-2466/13/10
