The clustering of insulin resistance, dysglycaemia, dyslipidaemia and hypertension was originally defined as syndrome X in 1988 (Reaven, 1988). Definitions of the metabolic syndrome that also include a measure of central obesity have been developed between 1999 and 2001 by the World Health Organization (WHO Consultation, 1999), the European Group for the Study of Insulin Resistance (EGIR; Balkau and Charles, 1999) and the National Cholesterol Education Program (NCEP) Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults [abbreviated to Adult Treatment Panel (ATP-III)] (NCEP Expert Panel on Detection, Evaluation, and Treatment of High Blood
Cholesterol in Adults, 2001). The ATP-III criteria also recognized the association between the above factors of the metabolic syndrome and both pro-inflammatory and pro-thrombotic states as reflected by increased C-reactive protein and plasma plasminogen activator inhibitor levels, respectively, but these are not required for definition of the syndrome (NCEP Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults, 2001). The factors involved in each of these definitions are summarized in Table 1.1. The International Diabetes Federation (IDF) produced a consensus worldwide definition of the metabolic syndrome in 2005 (available from www.idf.org) during the final stages of the preparation of this book. The criteria for this definition are a waist circumference of >94 cm for European men and >80 cm for European women (with lower cut-points
Table 1.1 Features of the World Health Organization (WHO), European Group for the Study of Insulin Resistance (EGIR) and National Cholesterol Education Program Expert Panel on Detection, Evaluation, and Treatment of High Blood Cholesterol in Adults (ATP-III) definitions of the metabolic syndrome
WHO (WHO Consultation, 1999) Impaired glucose tolerance or diabetes and/or insulin resistance and two of the other factors
EGIR (Balkau and Charles, 1999) Presence of fasting hyperinsulinaemia (the highest 25%) and two of the other factors
ATP-III (NCEP Expert Panel on Detection, 2001)
Three or more of the following factors (triglycerides and HDL counted separately)
Blood pressure (mmHg) Dyslipidaemia (mmoll-1)
WHR > 0.9 (men), 0.85 (women) and/ or BMI>30 kg m-2 >140/90
Triglycerides > 1.7 HDL <0.9 (men), <1.0 (women)
Fasting glucose > 6.1 and/or 2 h postchallenge glucose >7.8 on diabetes Glucose uptake during hyperinsulinamic euglycaemic clamp in lowest quartile for population
Microalbuminuria (urinary albumin excretion rate> 20 igmin-1 or albumin:creatinine ratio>30 mg g-1
> 140/90 or treated for hypertension Triglycerides >2.0 or HDL-cholesterol <1.0 or treated for dyslipidaemia Fasting plasma glucose > 6.1, but non-diabetic
Presence of fasting hyperinsulinaemia
(i.e. among the highest 25% of the non-diabetic population)
> 130/85 or treated for hypertension Triglycerides > 1.7 HDL-cholesterol: <1.0 (men), < 1.3 (women) Fasting plasma glucose > 6.1
Abbreviations: BMI, body mass index; HDL, high-density lipoprotein; WHR, waist:hip ratio.
for some other ethnic groups) and two or more of the folowing: blood pressure, triglyceride and HDL-cholesterol cut-points as for the ATP-III definition and fasting plasma glucose 5.6mmol/l. The application of this definition will increase the prevalence of the metabolic syndrome but its effect of risk of diabetes and cardiovascular disease has yet to be established and is not considered further here.
The major difference between criteria is that the WHO and EGIR criteria include a measure of insulin resistance as one of the components. The WHO criteria also require results of a glucose tolerance test, which means that they have been applied less frequently to large epidemiological or clinical studies in which often only the fasting glucose level is measured.
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