Prevalence of Obstructive Sleep Apnea in Asian Adults
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 assessment. Of these 676 articles were excluded after abstract screening for the following reasons: not focused on the studied outcomes (n-416), studies in pediatric population (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 articles covering 47,957 patients (26,042 men and 21,915 women) were eligible based on the aforementioned criteria. 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 assessment. The diagram of the literature search is shown in Figure 1.
(Enlarge Image)
Figure 1.
Flow chart of selected studies.
Ten manuscripts were community studies. These included 32,508 participants (17,580 women and 14,928 men): two studies from Turkey (n-6,117), two studies from Taiwan/China (n-5,263), two studies from Iran (n-4,056), one study each from Japan (n-8,483), Thailand (n-4,680), Singapore (n-2,298) and Malaysia (n-1,611). 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% to 27.3%, both from Iranian studies. This difference could be explained by the fact that the study with a lower prevalence 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 and the highest prevalence of 59.1% was in Taiwan. The study from Thailand included a much higher number of women and the population was younger than in the study from Taiwan/China. The lowest prevalence of witnessed apneas was 2.6% in Taiwan, and the highest was 15.2% in Malaysia. Symptoms of EDS ranged from 3.85% to 24%, both in Turkish studies. The difference in EDS prevalence could be explained by the different sample sizes and populations studied.
Male gender, older age, greater BMI and neck circumference, 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 quality, 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.
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), two studies from mainland China (3,302); four Japanese studies (n-3,475), two Indian studies (n-4,665), and one each from Korea (n-5,020), Malaysia (n-279) and Singapore (n-106). The summary of the studies is presented in Table 2.
Six studies used PSG, 2 studies used PSG and a sleep questionnaire, one study used a sleep questionnaire, home sleep monitoring and PSG, one study used home sleep study and PSG, one study used overnight pulse oximetry monitoring and PSG, one study used three channel home sleep monitoring and two studies used overnight pulse oximetry. The smallest sample consisted of 106 participants (Singaporean study), and the largest consisted of 2,505 participants (Indian study). Men were predominant studied group in most studies, whereas one study enrolled exclusively women.
The mean age of participants ranged from 41.2 years in the study from Hong-Kong/China to 58.6 years in the Japanese study. The mean BMI varied from 22.4 kg/m in the study from Hong-Kong/China to 29.4 kg/m in the Malaysian study. The study from Singapore did not report data on either mean age or mean BMI.
OSA prevalence ranged from 3.7% one Japanese study to 97.3% in another study from Japan. This huge difference 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. 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 to 72% in the study from Singapore. 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 impossible to extract the original article, since the journal in which it was published no longer exists.
Some studies reported the estimated OSA/OSAS prevalence, which ranged from 3.7%/2.1% in the study performed by Hong-Kong researchers in women to 13.74%/3.57% in the Indian study. The Indian study had a predominantly male sample, and the population was heavier and older than in the study from Hong-Kong, which recruited exclusively women and these factors can help explain the difference in estimated disease burden.
Male gender, older age, greater BMI, neck circumference 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 aforementioned studies.
Since the studies were of different methodological quality, tested different 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., Hui et al. and Reddy et al. 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.
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 assessment. Of these 676 articles were excluded after abstract screening for the following reasons: not focused on the studied outcomes (n-416), studies in pediatric population (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 articles covering 47,957 patients (26,042 men and 21,915 women) were eligible based on the aforementioned criteria. 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 assessment. The diagram of the literature search is shown in Figure 1.
(Enlarge Image)
Figure 1.
Flow chart of selected studies.
Community Studies Using Sleep Questionnaires
Ten manuscripts were community studies. These included 32,508 participants (17,580 women and 14,928 men): two studies from Turkey (n-6,117), two studies from Taiwan/China (n-5,263), two studies from Iran (n-4,056), one study each from Japan (n-8,483), Thailand (n-4,680), Singapore (n-2,298) and Malaysia (n-1,611). 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% to 27.3%, both from Iranian studies. This difference could be explained by the fact that the study with a lower prevalence 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 and the highest prevalence of 59.1% was in Taiwan. The study from Thailand included a much higher number of women and the population was younger than in the study from Taiwan/China. The lowest prevalence of witnessed apneas was 2.6% in Taiwan, and the highest was 15.2% in Malaysia. Symptoms of EDS ranged from 3.85% to 24%, both in Turkish studies. The difference in EDS prevalence could be explained by the different sample sizes and populations studied.
Male gender, older age, greater BMI and neck circumference, 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 quality, 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), two studies from mainland China (3,302); four Japanese studies (n-3,475), two Indian studies (n-4,665), and one each from Korea (n-5,020), Malaysia (n-279) and Singapore (n-106). The summary of the studies is presented in Table 2.
Six studies used PSG, 2 studies used PSG and a sleep questionnaire, one study used a sleep questionnaire, home sleep monitoring and PSG, one study used home sleep study and PSG, one study used overnight pulse oximetry monitoring and PSG, one study used three channel home sleep monitoring and two studies used overnight pulse oximetry. The smallest sample consisted of 106 participants (Singaporean study), and the largest consisted of 2,505 participants (Indian study). Men were predominant studied group in most studies, whereas one study enrolled exclusively women.
The mean age of participants ranged from 41.2 years in the study from Hong-Kong/China to 58.6 years in the Japanese study. The mean BMI varied from 22.4 kg/m in the study from Hong-Kong/China to 29.4 kg/m in the Malaysian study. The study from Singapore did not report data on either mean age or mean BMI.
OSA prevalence ranged from 3.7% one Japanese study to 97.3% in another study from Japan. This huge difference 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. 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 to 72% in the study from Singapore. 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 impossible to extract the original article, since the journal in which it was published no longer exists.
Some studies reported the estimated OSA/OSAS prevalence, which ranged from 3.7%/2.1% in the study performed by Hong-Kong researchers in women to 13.74%/3.57% in the Indian study. The Indian study had a predominantly male sample, and the population was heavier and older than in the study from Hong-Kong, which recruited exclusively women and these factors can help explain the difference in estimated disease burden.
Male gender, older age, greater BMI, neck circumference 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 aforementioned studies.
Since the studies were of different methodological quality, tested different 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., Hui et al. and Reddy et al. 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.
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