Asian Population and Sleep Apnea
Definition of Apnea
An apnea is defined as the complete cessation of airflow for at least 10 seconds. Apneas are further classified as obstructive, central, or mixed based on whether effort to breathe is present during the event. Obstructive sleep apnea is a chronic condition characterized by recurrent episodes of partial or complete collapse of the upper airway. The reduction of airflow often leads to problems in gas exchange and recurrent arousals from sleep. OSA is also associated with increased morbidity and mortality from cardiovascular causes, and traumatic accidents due to excessive daytime sleepiness.
Cardinal Manifestations of OSA
- Loud snoring
- Witnessed breathing pauses during sleep
- Fitful sleep quality
Risk Factors for OSA
- Obesity (an established major risk factor)
- Male sex
- Smoking and Alcohol Consumption
- Familial and Genetic Disposition
- Medical Comorbidity
- Craniofacial Anatomy
Health Consequences of Untreated OSA
- Excessive daytime sleepiness (EDS)
- Cognitive dysfunction
- Impaired work performance
- Decrements in health-related quality of life
Prevalence of OSA in the Asian Population
The Sleep Heart Health Study suggested common OSA symptoms such as snoring, witnessed apnea, and sleepiness differ substantially by race/ ethnicity.It is well known that South Asians manifest greater visceral adiposity, insulin resistance, and Diabetes Mellitus at a lower BMI compared to white because South Asians commonly develop adverse metabolic profiles at a lower BMI.
In an instance, Wang et al. compared the percentage of body fat and fat distribution between Caucasians and Chinese descendants living in New York City and observed that Asians had a lower BMI but a higher percentage of body fat and more upper-body subcutaneous fat than did whites. This suggests that the risk for OSA associated with obesity may be largely under-recognized among Asians. There may be a delay or under-diagnosis of OSA if a BMI >30 kg/m2 is considered to be the criterion for obesity in Asians. This concept was also acknowledged by the WHO and by the Japanese Society for the Study of Obesity that lowered the BMI cut-off for obesity among Asians from ≥30 to ≥25 kg/ m2.
In a recent study about Japanese descendants, patients with OSA referred to a sleep laboratory have a similar AHI but a significantly lower BMI than white patients. Studies that controlled for BMI conveyed a similar message, and showed a higher AHI in Asians compared to Caucasians. Therefore, Japanese descendant males are predisposed to OSA even though they are not obese according to the standard for Caucasians.
There is also evidence supporting the theory that Asians have an unfavorable anatomy. For instance, a shorter and steeper anterior cranial base angle, which may predispose to OSA, was observed among Asians with OSA compared to Caucasians. Such studies confirm that craniofacial abnormalities are important in pathogenesis of obstructive sleep apnea, particularly in non-obese patients.
On a report on the differences in the prevalence of OSA in severely obese South Asians and whites in a UK bariatric clinic where all patients underwent limited-channel home sleep testing, 13 South Asians had a higher prevalence of OSA (43%) than whites (22%) and a substantially greater apnea hypopnea index.
Sleep Medicine in Asian Countries
Despite the advancements in the understanding of the clinical consequences of sleep breathing disorders, a majority of those affected remain undiagnosed. Sleep medicine is in a developmental stage in many Asian countries and although sleep laboratories have been set-up in various countries in Asia, the availability of this service is very limited.
Little information is available regarding the success of specific OSA treatment options in South Asians. Continuous positive airway pressure is available in most parts of Asia, but financial constraints may limit its utility.
There is a great need for research and health care development on sleep disordered breathing in Asia, and therefore it is imperative to give medical education and instructions on the risks of obstructive sleep apnea and other sleep disorders. Given the high prevalence and public health burden of obstructive sleep apnea, the implications of untreated disease are enormous and cannot be ignored. The solution will only come with efforts towards promotion and awareness of this condition.
Genta, P.R., Marcondes, B.F., Danzi, N.J., & Lorenzi-Filho, G.. (2008). Ethnicity as a risk factor for obstructive sleep apnea: comparison of Japanese descendants and white males in São Paulo, Brazil. Brazilian Journal of Medical and Biological Research, 41(8), 728-733. Epub July 31, 2008.https://doi.org/10.1590/S0100-879X2008005000033
Lam, Buddie & Lam, David & Ip, M. (2007). Obstructive sleep apnea in Asia. The international journal of tuberculosis and lung disease : the official journal of the International Union against Tuberculosis and Lung Disease. 11. 2-11.
Kandula NR; Patel SR. Sleep apnea and cardiometabolic risk in South Asians. J Clin Sleep Med 2013;9(9):859-860.
Punjabi, N. M. The epidemiology of adult obstructive sleep apnea. Proceedings of the American Thoracic Society 5, 136–143, https://doi.org/10.1513/pats.200709-155MG (2008).