y Paul Zimmet, George Alberti, Jonathan Shaw

The metabolic syndrome is one of the major public health

issues of our time. The International Diabetes Federation

(IDF) believes that this cluster of factors is driving the

twin global epidemics of type 2 diabetes and cardiovascular

disease. If current trends continue, the premature deaths

and disabilities resulting from these conditions will cripple

the health budgets of many nations – both developed and

developing. People with the metabolic syndrome have three

times the risk of suffering a heart attack or stroke – and

twice the risk of dying from such an event – compared

with people without the syndrome. The authors explain the

reasoning behind the new IDF definition of the metabolic

syndrome, which many commentators have labelled ‘the

world’s latest epidemic’.

>>

obesity) as the type of obesity that was commonly associated with the metabolic abnormalities found in type 2 diabetes and cardiovascular disease.2

Since the first official definition of the metabolic syndrome by a working group of the World Health Organization (WHO) in 1999,3 a number of alternative definitions have been proposed.3 The most widely accepted of these have been produced by WHO, the European Group for the Study of Insulin Resistance,4 and the US National Cholesterol Education Program Adult Treatment Panel III.5

ConfusionHowever, the definitions differed not only in the proposed components but also in the cut-off points used for each component. This led to considerable confusion. This relates not only to the usefulness of the definition in the clinical setting, but also was apparent in attempts to compare the burden of the metabolic syndrome in different populations.6

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A new IDF worldwide definition A new IDF worldwide definition

of the metabolic syndrome: of the metabolic syndrome:

the rationale and the results

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This is not a new condition; our awareness of what we now call the metabolic syndrome goes back at least 80 years. It was first described in the 1920s by Kylin, a Swedish physician, as the association of high blood pressure

(hypertension), high blood glucose (hyperglycaemia) and gout.1 Marañón, a noted Spanish physician, also described it soon after. In 1947 in a classic paper, Vague drew attention to upper-body adiposity (‘android’ or ‘male-type’

( )

As a result, IDF identified an urgent need to rationalize the variety of definitions that had been developed for the condition. This need extended from clinical practice to research. With this in mind, IDF commissioned its Task Force on Epidemiology to gather experts from around the world in order to formulate a new worldwide definition of the metabolic syndrome.

ConsensusThe objective of this consensus group was to produce a new set of criteria for use both epidemiologically and in clinical practice worldwide in order to: identify people with the metabolic

syndrome better define the nature of the

syndrome focus on lifestyle and therapeutic

strategies to reduce the long-term risk of both cardiovascular disease and type 2 diabetes.

The consensus group produced new criteria for research into the metabolic syndrome.

One of the principal aims of this initiative was to provide guidance on ways in which to compensate for the differences in waist circumference and regional adipose tissue distribution that exist between different populations. The consensus group also produced recommendations for additional criteria that can be included when studying the metabolic syndrome for research purposes. Furthermore, the group identified areas where more studies are currently needed, particularly research into the origins of the syndrome.

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These are pragmatic cut-off points and better data are required to link them to risk. Ethnicity should be the basis for classification, not the country of residence.For ethnic South and Central Americans, South Asian recommendations should be applied until more specific data are available.For people of Sub-Saharan African origin and eastern Mediterranean and Arab populations, European data should be used until more specific data are available.

Country/ethnic group Waist circumference (cm)(as measure of central obesity)

Table 2: Country-/ethnicity-specific values for waist circumference

Europids

South Asians

Chinese

Japanese

≥ 94

≥ 80

≥ 90

≥ 80

≥ 90

≥ 80

≥ 85

≥ 90

Male

Female

Male

Female

Male

Female

Male

Female

Table 1: IDF metabolic syndrome worldwide definition

* If BMI is >30kg/m2, central obesity can be assumed and waist circumference does not need to be measured.** In clinical practice, impaired glucose tolerance is also acceptable, but all epidemiological reports of the prevalence of the

metabolic syndrome should use only the fasting plasma glucose and presence of previously diagnosed diabetes to assess this criterion. Prevalence also incorporating the two-hour glucose results can be added as supplementary findings.

Central obesity Waist circumference* – ethnicity specific

Plus any two of the following

Raised triglycerides

Reduced HDL-cholesterol

Raised blood pressure

Raised plasma glucose**

≥1.7 mmol/L (150 mg/dL)or specific treatment for this lipid abnormality

<1.03 mmol/L (40 mg/dL) in males<1.29 mmol/L (50 mg/dL) in femalesor specific treatment for this lipid abnormality

Systolic: ≥130 mmHg or diastolic: ≥85 mmHgor treatment of previously diagnosed hypertension

Fasting plasma glucose ≥5.6 mmol/L (100 mg/dL)or previously diagnosed type 2 diabetes

If above 5.6 mmol/L or 100 mg/dL, an oral glucose tolerance test is strongly recommended but is not necessary to define the presence of the syndrome.

( )

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The new IDF definition takes into account the mounting evidence that abdominal adiposity is common to each of the components of the metabolic syndrome. Under this new definition, an increased waist circumference – already a well accepted proxy measurement for abdominal adiposity – is a necessary requirement for the diagnosis of the metabolic syndrome (Table 1). This has an added advantage: a simple measurement of the waist serves as the first screening test for the syndrome, and can be done easily and cheaply anywhere in the world.

The new IDF definition provides different

obesity cut-off points for different

ethnic groups.

Research has shown that between population groups there exists a variation in the levels of obesity at which the risk of other health conditions begins to rise.6

Therefore, ethnicity-specific waist circumference cut-off points (see Table 2) have been incorporated into the new IDF definition.7

PreventionThe recognition of these features in people with type 2 diabetes has special importance: it indicates the need for the aggressive reduction of cardiovascular risk. Of course, it should be remembered that as with many previous attempts to define diagnostic criteria for obesity, diabetes, hypertension, and dyslipidaemia, there is a chance that fresh research will force changes in this new definition.

Fortunately, there are treatment regimens that can influence all of these risk factors. Most importantly: weight reduction and increased physical activity reduce insensitivity to insulin and improve glucose tolerance and other cardiovascular risk factors, such as raised levels of triglycerides and blood pressure. If these interventions are not effective, drugs are currently available to deal specifically with each of the abnormalities. New therapies continue to appear which may either deal with two or more of the abnormalities or help with weight loss.

ConclusionThe new IDF definition of the metabolic syndrome addresses both clinical and research needs. It also provides an accessible, diagnostic tool that is suitable for use in populations worldwide. Furthermore, this definition establishes a list of potential additional criteria that should be included in epidemiological studies and other research into the metabolic syndrome.

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y Paul Zimmet, George Alberti, Jonathan ShawJonathan Shaw

Paul Zimmet is currently Foundation Director Paul Zimmet is currently Foundation Director Paul Zimmet is currently Foundation Director

of the International Diabetes Institute, of the International Diabetes Institute, of the International Diabetes Institute,

Australia, a position he has held since Australia, a position he has held since Australia, a position he has held since

1985. He is Professor of Diabetes at Monash 1985. He is Professor of Diabetes at Monash 1985. He is Professor of Diabetes at Monash

University, Australia, and is a Professor at University, Australia, and is a Professor at University, Australia, and is a Professor at

Deakin University and the Graduate School of Deakin University and the Graduate School of Deakin University and the Graduate School of

Public Health, University of Pittsburgh, USA.Public Health, University of Pittsburgh, USA.Public Health, University of Pittsburgh, USA.

ReferencesReferences1 Kylin E. Studien ueber das Hypertonie-Hyperglyka 1 Kylin E. Studien ueber das Hypertonie-Hyperglyka

“mie-Hyperurika” miesyndrom. “mie-Hyperurika” miesyndrom. Zentralblatt fuer Innere MedizinMedizin 1923; 44: 105-27.

2 Vague J. Sexual Differentiation. A Factor Affecting the 2 Vague J. Sexual Differentiation. A Factor Affecting the Forms of Obesity. Forms of Obesity. Presse Med 1947; 30: 339-40.Presse Med 1947; 30: 339-40.Presse Med

3 World Health Organization. Definition, diagnosis and 3 World Health Organization. Definition, diagnosis and classification of diabetes mellitus and its complications. classification of diabetes mellitus and its complications. Report of a WHO consultation 1999.Report of a WHO consultation 1999.

4 Balkau B, Charles MA. Comment on the provisional 4 Balkau B, Charles MA. Comment on the provisional report from the WHO consultation. European Group report from the WHO consultation. European Group for the Study of Insulin Resistance (EGIR). for the Study of Insulin Resistance (EGIR). Diabet Med1999; 16: 442-3.1999; 16: 442-3.

5 Executive Summary of The Third Report of The National 5 Executive Summary of The Third Report of The National Cholesterol Education Program (NCEP) Expert Panel on Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, And Treatment of High Blood Detection, Evaluation, And Treatment of High Blood Cholesterol In Adults (Adult Treatment Panel III). Cholesterol In Adults (Adult Treatment Panel III). JAMA2001; 285: 2486-97.2001; 285: 2486-97.

6 Eckel RH, Grundy SM, Zimmet PZ. The metabolic 6 Eckel RH, Grundy SM, Zimmet PZ. The metabolic 6 Eckel RH, Grundy SM, Zimmet PZ. The metabolic syndrome. syndrome. Lancet 2005; 365: 1415-28.Lancet 2005; 365: 1415-28.Lancet

7 The IDF consensus worldwide definition of the metabolic 7 The IDF consensus worldwide definition of the metabolic syndrome. http://www.idf.org/webdata/docs/IDF_syndrome. http://www.idf.org/webdata/docs/IDF_Metasyndrome_definition.pdf.Metasyndrome_definition.pdf.

George Alberti is Senior Research Fellow George Alberti is Senior Research Fellow George Alberti is Senior Research Fellow George Alberti is Senior Research Fellow George Alberti is Senior Research Fellow

at Imperial College, London, and National at Imperial College, London, and National at Imperial College, London, and National at Imperial College, London, and National at Imperial College, London, and National

Director for Emergency Care in England.Director for Emergency Care in England.Director for Emergency Care in England.

Jonathan Shaw is Deputy Director of the Jonathan Shaw is Deputy Director of the Jonathan Shaw is Deputy Director of the

International Diabetes Institute, Australia, International Diabetes Institute, Australia, International Diabetes Institute, Australia,

and Associate Professor in the Departments and Associate Professor in the Departments and Associate Professor in the Departments and Associate Professor in the Departments and Associate Professor in the Departments

of Medicine, and Epidemiology and Preventive of Medicine, and Epidemiology and Preventive of Medicine, and Epidemiology and Preventive of Medicine, and Epidemiology and Preventive of Medicine, and Epidemiology and Preventive

Medicine at Monash University, Australia.Medicine at Monash University, Australia.Medicine at Monash University, Australia.

AcknowledgementsAcknowledgementsThe IDF metabolic syndrome consensus The IDF metabolic syndrome consensus definition process was supported by an definition process was supported by an educational grant from AstraZeneca educational grant from AstraZeneca Pharmaceuticals.Pharmaceuticals.

The new IDF worldwide definition of the The new IDF worldwide definition of the metabolic syndrome is available at: metabolic syndrome is available at: www.idf.org