An Investigation into the Relationship Between Sleep-Disordered Breathing, the Metabolic Syndrome, Cardiovascular Risk Profiles, and Inflammation Between South Asians and Caucasians Residing in the United Kingdom
Department of Diabetes Research, University Hospitals of Leicester, NHS Trust, Leicester, United Kingdom. Metabolic syndrome and related disorders
(Impact Factor: 1.98).
01/2012; 10(2):152-8. DOI: 10.1089/met.2011.0073
The aim of this study was to determine the prevalence of sleep-disordered breathing (SDB) in a South Asian and a Caucasian population and to compare the cardiovascular risk factors in those with SDB within these ethnic groups and determine if SDB is independently associated with the metabolic syndrome and markers of inflammation.
A total of 1,598 participants within a U.K. multiethnic population underwent an oral glucose tolerance test, completed the Berlin Sleep Questionnaire, and provided anthropometric data and fasting bloods. Metabolic syndrome was classified according to National Cholesterol Education Program Adult Treatment Panel III criteria.
The prevalence of SDB was 28.3% and did not differ between the two ethnic groups. South Asians with SDB had a higher body fat percentage (38.4±10% vs. 35.6±9%, P=0.016), glycosylated hemoglobin (5.6±0.5% vs. 5.6±0.5%, P=0.001) and lower high-density lipoprotein cholesterol (1.21±0.23 mmol/L vs. 1.29±0.34 mmol/L, P=0.002) compared to Caucasians with SDB, who were older (59.6±8.6 years vs. 50.4±10.3 years, P<0.001) and had higher systolic blood pressure (139.8±18.5 mmHg vs. 131.7±18.6 mmHg, P<0.001). SDB was associated with metabolic syndrome after adjustment for age, gender, ethnicity, and waist circumference (odds ratio=1.54, 95% confidence interval 1.12-2.09, P=0.01). There was no independent association between SDB and markers of inflammation.
The relationship between SDB and metabolic syndrome is not driven via the inflammatory pathway. The prevalence of SDB is significantly higher in those with metabolic syndrome although these South Asians had a greater cardiovascular disease (CVD) risk profile the relationship is independent of ethnicity. Routine screening for SDB within primary/secondary care may have a role in the prevention of CVD and type 2 diabetes mellitus.
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ABSTRACT: Questions have been raised concerning the clinical value of the metabolic syndrome (MS). The negative opinion regarding MS is basically anchored on a separate analysis of four conditions: obesity, dyslipidemia, hypertension and glucose intolerance. The common denominator of these four sets of arguments is that they represent an utterly simplistic view of MS as a solely predictive tool of morbidity or mortality. We believe that it is inequitable to compare it with statistically constructed predictive tools, including stronger prognostic variables even unrelated to each other from the biological point of view. Several recent large meta-analyses - one of them including near one million patients - had systematically shown that people with MS are at increased risk of cardiovascular events. MS was associated with a 2-fold increase in cardiovascular outcomes and a 1.5-fold increase in all-cause mortality rates. A very important finding was that cardiovascular risk remained still high in patients with MS but without diabetes. The presence of MS possesses a definite predictive value, but first of all it is a widely accepted concept regarding a biological condition based on the complex and interrelated pathophysiological mechanisms emanating from excess central adiposity and insulin resistance. The risk factors are multiplicative, meaning that the risk for cardiovascular disease from risk factors rises geometrically, not linearly, as the number of risk factors increases. Therefore, currently available evidences strongly support the concept of the MS as a critical clustering of cardiovascular risk factors and diabetes, representing a true and solid evolving clinical entity.
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ABSTRACT: Study objectives:
The South Asian population is at increased risk of cardiovascular disease. We compared the prevalence and severity of obstructive sleep apnea (OSA) in South Asians and white Europeans with severe obesity.
Data from consecutive patients attending a specialist weight management service were analyzed. Self-reported age, gender, and ethnicity were recorded. Objective measurements of blood pressure, body mass index (BMI), and apneahypopnea index (AHI) were also acquired.
A total of 308 patients (72.7% women; 13% South Asian) were included, with mean age and BMI of 46 ± 12 y and 49 ± 8 kg/m2, respectively. South Asians had significantly increased prevalence of OSA compared to white Europeans (85% vs. 66% [p = 0.017]) and were more likely to have severe OSA (42.5% vs. 21.6% [p = 0.015]). South Asians had significantly higher median AHI (24 events/h: interquartile range [IQR] 9.3-57.6 vs. 9 events/h: IQR 3.4-26.6; p < 0.01), significantly lower minimum oxygen saturation (76%: IQR 64% to 84% vs. 83%: IQR 77% to 87%; p < 0.01), and spent a significantly greater amount of time < 90% oxygen saturation (8.4%: IQR 1.0% to 24.3% vs. 2.4%: IQR 0.2% to 16.0%; p = 0.03). South Asian ethnicity, independent of demographics, BMI, and comorbidities, was associated with β = 1.84 (95% CI: 1.27-2.65) increase in AHI+1 compared to white Europeans. Furthermore, we confirmed other independent OSA risk factors including increasing age, BMI, and male gender (all p < 0.001).
Severely obese South Asians had significantly greater prevalence and severity of OSA than white Europeans. OSA may contribute to increased cardiovascular risk in South Asians compared to white Europeans with severe obesity. Mechanisms mediating the observed associations between these ethnicities require further investigation.
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