Review Article Indian J Med Res 131, February 2010, pp 171-175
Epidemiology of adult obstructive sleep apnoea syndrome in India Surendra K. Sharma & Gautam Ahluwalia*
Department of Medicine, All India Institute of Medical Sciences, New Delhi & *Department of Medicine Dayanand Medical College & Hospital, Ludhiana, India
Received August 10, 2009 There is a paucity of published Indian studies on the prevalence and risk factors of obstructive sleep apnoea (OSA) in adults. The limited published literature, however, does not suggest significant differences in the prevalence and risk factors for OSA and obstructive sleep apnoea syndrome (OSAS) as compared to western studies. Well designed studies are required from all parts of India. Patients should be screened carefully before referring them to costly investigations such as overnight polysomnography. With the background of increasing urbanization, fast growing economy and changes in lifestyle, India will have an epidemic of obesity. Therefore, future studies on the association of OSA and metabolic syndrome should carefully evaluate confounding effect of obesity on metabolic abnormalities in patients with OSA. Key words obesity - obstructive sleep apnoea - OSAS - prevalence - risk factors
Prevalence in Indian subcontinent
In India, the obesity epidemic will propel obstructive sleep apnoea syndrome (OSAS) to an increasingly important public health issue over the next few years. The future areas of sleep research in our country will have to focus on the cause and effect relationship of OSAS with obesity related co-morbid diseases like type 2 diabetes mellitus, coronary artery disease, congestive heart failure, hypertension, chronic kidney disease, dyslipidaemias and metabolic syndrome as applicable to the Indian population.
In 2006, a population-based survey from north India had estimated the prevalence of OSAS at 3.6 per cent (males and females being 4.9 and 2.1% respectively)1. The prevalence of OSA in the same study was 13.7 per cent. However, this prevalence study was conducted in a semi-urban Indian population with a small sample size without adequately studying different socio-economic strata. In India, no epidemiological research can be representative of its population until it includes subjects with diverse economic background. Recently, prevalence and risk factors of OSAS in different socioeconomic classes in an urban Indian population have been reported from South Delhi2. The authors observed a prevalence of OSA to be 9.3 per cent and OSAS to be 2.8 per cent. The prevalence rates of OSA and OSAS in
In a resource limited setting like India, there is a paucity of health care facilities with multi-channel polysomnography equipment, thereby further limiting the evaluation of OSAS patients. In spite of the constraints, researchers in India and its neighbouring countries in the last decade have made a preliminary attempt to study OSAS and co-morbid conditions. 171
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males were 13.4 and 4 per cent respectively whereas in females, these were 5.6 and 1.5 per cent respectively2. Another hospital-based study from north India revealed an estimated prevalence of OSA and OSAS to be 4.4 and 2.4 per cent in males, whereas it was 2.5 and 1 per cent in females3.
In a hospital-based study of urban men between 35 and 65 yr from western India, the prevalence of OSA was 19.5 per cent and of OSAS was 7.5 per cent4. This study was performed only in men belonging to a higher socio-economic status with a home-based polysomnography (PSG) study, which introduced an
Table. Worldwide prevalence of adult obstructive sleep apnoea Author (Reference)
Hospital- or communitybased Questionnaire study (n)
Study design
OSA (%)
Unsupervised Fully supervised Overall home PSG (n) PSG in lab (n)
OSAS (%)
M
F
Overall
M
F
Gislason et al10 1988, Sweden
Community
Yes (3252)
Not done
Yes (61)
-
3
-
-
1.4
-
Young et al5 1993, USA
Community
Yes (3515)
Not done
Yes (602)
16.5
24
9
2
4
2
Bearpark et al11 1994, Australia
Community
No
Yes (294)
No
-
26
-
-
3.1
-
Olson et al12 1994, Australia
Community
Yes (441)
Not done
Yes (441)
13.5
-
-
4.2
-
-
Bixler et al13 2001, USA
Community
Yes (16 583)
Not done
Yes (741)
4.7
7.2
2.2
2.5
3.9
1.2
Duran et al14 2001, Spain
Community
Yes (2148)
Not done
Yes (555)
27
28
26
3.2
3.4
3
Ip et al8 2001, China
Community
Yes (784)
Not done
Yes (153)
-
8.8
-
-
4.1
-
Huang et al16 2003, China
Community
Yes (8081)
Yes (150)
No
20.4
-
-
3.6
-
-
Kim et al17 2004, Korea
Community
Yes (5020)
Not done
Yes (457)
-
27
16
-
4.5
3.2
Ip et al9 2004, China
Community
Yes (854)
Not done
Yes (106)
-
-
3.7
-
-
2.1
Udwadia et al4 2004, India
Hospital
Yes (658)
Yes (250)
No
-
19.5
-
-
7.5
-
Sharma et al1 2006, India
Community
Yes (2150)
Not done
Yes (150)
13.7
19.7
7.4
3.6
4.9
2.1
Vijayan & Patial3 2006, India
Community
Yes (7975)
Not done
Yes (47)
3.5
4.4
2.5
1.7
2.4
1
Taj et al6 2008, Pakistan
Hospital
Yes (450)
Not done
No
Taj et al7 2009, Pakistan
Hospital
Yes (137)
Not done
No
Adewole et al15 2009, Nigeria Reddy et al2 2009, India
Community
Yes (370) Yes (2505)
Not done
No
Not done
Yes (365)
Community
10% high risk for sleep apnoea 12.4% high risk for sleep apnoea 19% high risk for sleep apnoea 9.3
13.5
5.6
2.8
4
1.5
OSA, obstructive sleep apnoea; OSAS, obstructive sleep apnoea syndrome; PSG, polysomnography; M, males; F, females; n-number of subjects
Sharma & Ahluwalia: OSAS epidemiology in India
element of selection bias. The Table provides worldwide prevalence of obstructive sleep apnoea. It can be concluded that prevalence of OSAS in communitybased Indian epidemiological studies is similar to those reported in the western population5. In preliminary studies from Pakistan based on Berlin questionnaire, overall prevalence of individuals who had high risk for sleep apnoea, was observed between 10 to 12.4 per cent6,7. These observations are not surprising due to the increasing sedentary lifestyle in both urban and rural communities in the oriental population resulting in similar lifestyle-related diseases which till now were a burden of the economically developed nations only. The craniofacial anatomy in the oriental population also predisposes individuals to OSA18. The prevalence of OSA in the Indian population is three-fold higher in men as compared to women2. The prevalence of OSA increases with age, though age is not an independent risk factor for the OSA2. Risk factor association vis-à-vis causation in Indian population In India, obese individuals have nearly four times higher risk of having OSA as compared to non obese individuals independent of age and gender1. Syndrome Z is defined as co-occurrence of OSA and metabolic syndrome. The estimated population prevalence of syndrome Z in north India was about 4.5 per cent (95% CI 3.7-5.3) and age, male gender, % body fat and nocturnal desaturation were independent risk factors19,20. There has been evidence from western studies that metabolic abnormalities of dyslipidaemia, insulin resistance, leptin and adiponectin levels have an independent association with OSAS21. Interestingly, a well conducted study from India has not observed any independent association between OSAS and these metabolic abnormalities22. Similar findings have been observed in India regarding the lack of correlation between raised serum high-sensitivity C-reactive protein and OSAS23. The results of these studies suggest the important role of confounding factors like obesity causing a spurious association, which should be an important area of future research before OSAS is conclusively labelled as an independent manifestation of these metabolic abnormalities. Hypothyroidism as a secondary cause of obesity also predisposes to OSAS. In fact, hypothyroidism and OSAS have common manifestations in the form of obesity, excessive daytime somnolence and apathy.
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Though hypothyroidism was considered a relatively infrequent cause of OSAS in the west, a study from India has demonstrated OSA in 30 per cent of patients with primary hypothyroidism24. Moreover, this study has also shown that OSAS was completely reversible with adequate thyroxine replacement therapy. The consequences of OSAS include hypertension, coronary artery disease, atrial fibrillation, cerebrovascular accidents, sudden death and neuropsychiatric manifestations25. However, in Indian population, hypertension did not have an independent association with OSA, though it was significantly more common in patients with OSA2. In recent times, the relationship between sleep apnoea and traffic accidents has assumed great importance. India has possibly the largest number of road traffic accidents in the world. Rates of traffic accidents were two to three times higher in individuals with sleep apnoea compared to the general population in the studies from the West, and the association remains significant even after adjustment for many potential confounding factors for accidents including alcohol consumption, age, driving experience, sleep schedule and use of drugs causing drowsiness26. Further longitudinal studies are required to elucidate the complex relationship of these factors in Indian subjects. The quantum of the problem in a resource-limited setting like India should be even more dismal as OSAS related daytime somnolence is further compounded by poor road infrastructure, lenient implementation of traffic rules and substandard vehicle maintenance as a cause of road accidents. In north Indian subjects, the combination of male gender, waist-hip ratio and neck circumference has been incorporated in a diagnostic model for predicting OSA and screening subjects for PSG27. The sensitivity, specificity, positive and negative predictive value of this model were 89, 90, 87 and 91 per cent respectively. Another diagnostic model by the same group incorporated body mass index, male gender, relativereported snoring index and choking index with a sensitivity, specificity, positive and negative predictive value of 82, 91, 89 and 84.5 per cent respectively28. In fact, a modified Berlin questionnaire has been designed by the investigators from New Delhi to screen patients prior to polysomnography in a resource limited setting like India29. This questionnaire is being validated by several researchers in different ethnic populations all over the world.
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Current ongoing research and economic issues in India The therapeutic strategy for management of OSAS includes nasal continuous positive airway pressure (nCPAP), besides other measures including a methodical weight loss programme for the patient30. In fact, two prospective intervention studies are being conducted in north India to study the cause and effect relationship of CPAP, metabolic syndrome and OSAS31,32. However, in a resource-limited setting in India, the cost of CPAP machine needs to be subsidized. Moreover, reimbursement policy by the health insurance companies or employee health coverage programme is another important issue which needs to be addressed by the national policy makers. references 1.
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30. Marin JM, Carrizo SJ, Vicente E, Aqusti AGN. Long-term cardiovascular outcomes in men with obstructive sleep apnoea-hypopnoea with or without treatment with continuous positive airway pressure: an observational study. Lancet 2005; 365 : 1046-53. 31. Sharma SK. Prevalence of metabolic syndrome in obstructive sleep apnoea and effect of treatment with auto-continuous positive airway pressure (CPAP) on metabolic syndrome. ClinicalTrials.gov registration number: NCT00694616. http:// clinicaltrials.gov/ct2/results?term=NCT00694616. 32. Sharma SK. Effect of continuous positive airway pressure (CPAP) on cardiovascular biomarkers in patients with obstructive sleep apnoea. ClinicalTrials.gov registration number (registration no. under process). http://clinicaltrials.gov.
Reprint requests: Prof. S.K. Sharma, Chief, Division of Pulmonary, Critical Care & Sleep Medicine, Chairman, Department of Medicine All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110 029, India e-mail:
[email protected];
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