The metabolic syndrome

The "metabolic syndrome" (MetS) is a clustering of components that reflect overnutrition, sedentary lifestyles, and resultant excess adiposity. The MetS includes the clustering of abdominal obesity, insulin resistance, dyslipidemia, and elevated blood pressure and is associated with other comorbidities including the prothrombotic state, proinflammatory state, nonalcoholic fatty liver disease, and reproductive disorders. Because the MetS is a cluster of different conditions, and not a single disease, the development of multiple concurrent definitions has resulted. The prevalence of the MetS is increasing to epidemic proportions not only in the United States and the remainder of the urbanized world but also in developing nations. Most studies show that the MetS is associated with an approximate doubling of cardiovascular disease risk and a 5-fold increased risk for incident type 2 diabetes mellitus. Although it is unclear whether there is a unifying pathophysiological mechanism resulting in the MetS, abdominal adiposity and insulin resistance appear to be central to the MetS and its individual components. Lifestyle modification and weight loss should, therefore, be at the core of treating or preventing the MetS and its components. In addition, there is a general consensus that other cardiac risk factors should be aggressively managed in individuals with the MetS. Finally, in 2008 the MetS is an evolving concept that continues to be data driven and evidence based with revisions forthcoming.

The Metabolic Syndrome

Metabolic syndrome (MetS) is a complex disorder defined by a cluster of interconnected factors that increase the risk of cardiovascular atherosclerotic diseases and diabetes mellitus type 2. Currently, several different definitions of MetS exist, causing substantial confusion as to whether they identify the same individuals or represent a surrogate of risk factors. Recently, a number of other factors besides those traditionally used to define MetS that are also linked to the syndrome have been identified. In this review, we critically consider existing definitions and evolving information, and conclude that there is still a need to develop uniform criteria to define MetS, so as to enable comparisons between different studies and to better identify patients at risk. As the application of the MetS model has not been fully validated in children and adolescents as yet, and because of its alarmingly increasing prevalence in this population, we suggest that diagnosis, prevention and treatment in this age group should better focus on established risk factors rather than the diagnosis of MetS.

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Metabolic syndrome: definitions and controversies

This systematic review collated seventy-eight studies exploring waist-to-height ratio (WHtR) and waist circumference (WC) or BMI as predictors of diabetes and CVD, published in English between 1950 and 2008. Twenty-two prospective analyses showed that WHtR and WC were significant predictors of these cardiometabolic outcomes more often than BMI, with similar OR, sometimes being significant predictors after adjustment for BMI. Observations from crosssectional analyses, forty-four in adults, thirteen in children, supported these predictions. Receiver operator characteristic (ROC) analysis revealed mean area under ROC (AUROC) values of 0·704, 0·693 and 0·671 for WHtR, WC and BMI, respectively. Mean boundary values for WHtR, covering all cardiometabolic outcomes, from studies in fourteen different countries and including Caucasian, Asian and Central American subjects, were 0·50 for men and 0·50 for women. WHtR and WC are therefore similar predictors of diabetes and CVD, both being stronger than, and independent of, BMI. To make firmer statistical comparison, a meta-analysis is required. The AUROC analyses indicate that WHtR may be a more useful global clinical screening tool than WC, with a weighted mean boundary value of 0·5, supporting the simple public health message ‘keep your waist circumference to less than half your height’. Waist-to-height ratio: Waist circumference: BMI: Central obesity: Abdominal obesity: Obesity

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A systematic review of waist-to-height ratio as a screening tool for the prediction of cardiovascular disease and diabetes: 0·5 could be a suitable global boundary value

Objective: To describe the relative validity and reliability of the FFQ used for assessing nutrient intakes of participants in the Tehran Lipid and Glucose Study (TLGS). Design: A total of 132 subjects (sixty-one males and seventy-one females) were included in the study. Dietary data were collected monthly by means of twelve 24h dietary recalls (24hDR). Subjects completed two, 168-item semi-quantitative FFQ. Blood and urine samples were taken every season for measurement of plasma biomarkers and urinary N and K. Results: Mean age and BMI of the participants were 35? 5( SD 16?8) years and 25? 5( SD 5?2) kg/m 2 , respectively. The mean energy-adjusted and deattenuated correlation coefficients for overall nutrient intake between the 24hDR and FFQ2 were 0?44 and 0?37 in #35-year-olds and .35-year-olds, respectively, and for individual nutrients ranged from 0?24 to 0?71 in men (mean r 50?53) and from 0?11 to 0?60 in women (mean r 50?39). The mean energy-adjusted reliability coefficients varied from 0?48 in #35-year-olds to 0?65 in .35-year-olds, and ranged from 0?41 to 0?79 in men (mean r 50?59) and from 0?39 to 0?74 in women (mean r 50?60). The FFQ2 and 24hDR produced exact agreement rates ranging between 39?6% and 68?3% in men and between 39?6% and 54?1% in women. The ranges of questionnaire validity coefficients, with the sample correlation between the questionnaires and biochemical marker as the lower limit and the estimate obtained by the method of triads as the upper limit, were 0?21‐0?56 (protein) and 0?37‐0?61 (K). Conclusions: The FFQ developed for the TLGS has reasonable relative validity and reliability for nutrient intakes in Tehranian adults.

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Reliability and relative validity of an FFQ for nutrients in the Tehran lipid and glucose study

Appropriate Definition of Metabolic Syndrome among Iranian Adults: Report of the Iranian National Committee of Obesity

Prevalence of metabolic syndrome in Iranian adult population, concordance between the IDF with the ATPIII and the WHO definitions

To determine cutoff points of anthropometric variables for predicting incident cardiovascular disease (CVD) in Iranian adults. It is a population-based longitudinal study. A total of 1614 men and 2006 women, aged ⩾40 years, free of CVD at baseline were included in the study. Body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), waist-to-height ratio (WHtR) and cardiovascular risks were assessed. Incident CVD was ascertained over a median of 7.6 years follow-up. The adjusted hazard ratios (HRs) for CVD were calculated for 1 s.d. change in all obesity variables using Cox proportional hazards regression analysis. Receiver operator characteristic (ROC) curve analysis was used as the method of defining the points of the maximum sum of sensitivity and specificity (MAXss) of each variable as a predictor of CVD. We found 333 CVD events during follow-up. The risk-factor-adjusted HRs were significant for all anthropometric variables in males and WHR in females and were 1.19, 1.24, 1.21 and 1.24 for BMI, WC, WHR and WHtR in males and 1.27 for WHR in females, respectively (all P 60 years old, all the anthropometric variables showed same CVD predicting power. The cutoff values (MAXss) for CVD prediction in males and females were BMIs 26.95 and 29.19 kg m−2,WCs 94.5 and 94.5 cm, WHRs 0.95 and 0.90, and WHtR 0.55 and 0.62, respectively. There was no difference between central obesity variables in predicting CVD in males, whereas in females WHR and WHtR were more appropriate. The cutoff values of anthropometric variables were higher in the Iranian than in other Asian populations.

Appropriate cutoff values of anthropometric variables to predict cardiovascular outcomes: 7.6 years follow-up in an Iranian population.

Objective: To investigate whether central obesity variables are more important than general obesity variables in predicting the incidence of type 2 diabetes in Iranians. Methods: In this population-based longitudinal study, a representative sample of 1852 males aged > 20 years, participants of the Tehran Lipid and Glucose Study, were followed for a mean duration of 3.6 years. Demographic data were collected; blood pressure and anthropometric variables such as body mass index (BMI), waist circumference (WC), waist-to-hip ratio (WHR), and waist-to-height ratio (WHtR) were measured according to a standard protocol. Biochemical analyses including measurements of plasma glucose in the fasting state and 2 hours after ingestion of 75 g glucose as well as fasting serum lipids were done. Diabetes and abnormal glucose tolerance (impaired fasting glucose or impaired glucose tolerance) were defined according to ADA criteria. Logistic regression models with the stepwise conditional method were used to estimate the relative risk (RR) of developing diabetes associated with each quartile of each anthropometric variable in a multivariate model adjusted for age, hypertension, smoking, family history of diabetes (model 1), and a full model adjusted for all the variables in model 1 plus abnormal glucose tolerance (model 2). Receiver operating characteristic (ROC) curves were used to determine the predictive power of each variable for development of type 2 diabetes, after adjustment for age. Results: A total of 69 new cases of type 2 diabetes (3.7%) were diagnosed during 3.6 years of follow-up, with an incidence rate of approximately one percent per year. The RR of developing diabetes associated with the highest quartile ofanthropometric variables, was highest for WHtR in model 1. After further adjustment for abnormal glucose tolerance (model 2) only WHtR and WC were significantly associated with type 2 diabetes. According to the ROC curve analysis, among central obesity variables only WHtR had a higher ROC curve than BMI. WHtR also continued to be the best predictive central obesity variable compared to BMI, even when the analysis was restricted to subjects with BMI <27 kg/m 2 (0.678 vs. 0.631, p<0.05). In those with BMI ≥27 kg/m 2 , none of the central obesity variables proved to be superior to BMI. Conclusion: Among abdominal obesity variables, WHtR appears to be stronger than BMI in identifying men with type 2 diabetes in the future.

Waist/height ratio as a better predictor of type 2 diabetes compared to body mass index in Tehranian adult men--a 3.6-year prospective study.

Introduction: To determine the prevalence of the metabolic syndrome (MS) in an Iranian elderly population and show its association with coronary heart disease (CHD). Materials and Methods: This is a cross-sectional study on 720 Iranian men and women aged ≥65 years who participated in the Tehran Lipid and Glucose Study (TLGS). Logistic regression analysis was used to estimate the odds ratio (OR) of developing CHD in model 1, an age-adjusted model; model 2, adjusted for age, smoking status, premature history of CHD and low-density lipoprotein (LDL) cholesterol; and model 3, adjusted for mentioned variables plus the MS components. Results: The prevalence of MS was 50.8%, 41.8% and 41.9% based on the Adult Treatment Panel (ATPIII), the World Health Organisation (WHO), and the International Diabetes Federation (IDF) definitions, respectively. The IDF definition showed high agreement with the ATPIII definition. Age-adjusted OR (95% CI) of the MS for CHD was 1.6 (1.2 to 2.2) by both the ATPIII and WHO definitions and 1.4 (1.0 to 1.9) by the IDF definition. IDF-defined MS lost its association with CHD in model 2. In model 3, obesity (WHO definition) and high blood pressure (ATPIII and WHO definitions) were associated with CHD. Conclusions: In an elderly Iranian population MS is highly prevalent. ATPIII and WHO definitions seem to be more pertinent than IDF for screening CHD risk. None of these definitions showed association with CHD when considering their components. Ann Acad Med Singapore 2009;38:142-9

Prevalence of metabolic syndrome by the Adult Treatment Panel III, International Diabetes Federation, and World Health Organization definitions and their association with coronary heart disease in an elderly Iranian population.

Azadeh Zabetian

Papers

Appropriate Definition of Metabolic Syndrome among Iranian Adults: Report of the Iranian National Committee of Obesity

Prevalence of metabolic syndrome in Iranian adult population, concordance between the IDF with the ATPIII and the WHO definitions

Appropriate cutoff values of anthropometric variables to predict cardiovascular outcomes: 7.6 years follow-up in an Iranian population.

Waist/height ratio as a better predictor of type 2 diabetes compared to body mass index in Tehranian adult men--a 3.6-year prospective study.

Prevalence of metabolic syndrome by the Adult Treatment Panel III, International Diabetes Federation, and World Health Organization definitions and their association with coronary heart disease in an elderly Iranian population.