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The metabolic syndrome
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The metabolic syndrome describes the clustering of
factors including dyslipidaemia, glucose intolerance and
hypertension with central adiposity. The syndrome is
increasing in prevalence worldwide as a consequence of
increasing obesity prevalence. Metabolic syndrome is
likely to have a marked impact on the prevalence of
cardiovascular disease and type 2 diabetes worldwide in
the next two decades. |
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Population data and definitions of metabolic
syndrome
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The clustering of impaired glucose tolerance,
hypertension, hypertriglyceridaemia and
hypercholesterolaemia was first described by Reaven in
1988.(1) He postulated that insulin resistance was the
cause of glucose intolerance, hyperinsulinaemia,
increased VLDL, decreased HDL and hypertension but he
did not include obesity in his original description.
It has since been realised that obesity is often the
cause of the insulin resistance that leads to the
metabolic abnormalities.(2)
There have been several definitions of the syndrome
(Table I (3-5)) but the most commonly used at present
are the World Health Organisation (WHO). (5) The WHO
criteria are central obesity with a waist: hip ratio
above 0.9 for men and 0.85 for women and/or a body mass
index (BMI) above 30 kg/m2, blood pressure above 140/90,
triglycerides above 1.7 mmol/L, HDL cholesterol <0.9
mmol/L in men and <1 mmol/L in women, glucose fasting or
2 h after a glucose load above 7.8 mmol/L and glucose
uptake during hyperinsulinaemic euglycaemic clamp in
lowest quartile for population.
The ATP III definition requires 3 of: waist
circumference ≥102 cm (men) or ≥88 cm (women); blood
pressure ≥130/85; HDL-cholesterol <40 mg/dL (men) or <50
mg/dL (women); triglycerides ≥150 mg/dL; fasting glucose
≥110 mg/dL. In April 2005, the International Diabetes
Federation produced a consensus on the definition of the
metabolic syndrome which includes central obesity and 2
metabolic sequaelae. Central obesity is defined by waist
circumference and differs between ethnic groups with
limits of 94 and 80 cm respectively for white European
men and women but 90 and 80 cm for South Asian or
Chinese individuals. Triglycerides, HDL and blood
pressure have the same limits as the ATP III definition
but glucose intolerance is defined as a fasting plasma
glucose ≥5.6 mmol/L (100 mg/dL) or a pre-existing
diagnosis of impaired glucose tolerance or diabetes.
This classification has not yet come into common usage.
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| TABLE I.—Definitions of the metabolic syndrome. |
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Syndrome X (1) |
Metabolic syndrome (3)
Impaired glucose tolerance or diabetes and/or
insulin resistance and 2 of the other factors |
Insulin resistance syndrome (4)
Presence of fasting hyperinsulinaemia factors
(the highest 25%) and 2 of the other factors |
Metabolic syndrome (5) Three or
more of the following factors (triglycerides and
HDL counted separately) |
International Diabetes Federation
Central obesity and 2 other factors www.idf.org |
Resistance to
insulin
stimulated
glucose uptake
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Under
hyperinsulinaemic,
euglycaemic conditions,
glucose uptake
below lowest quartile
for background population
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Insulin resistance
(highest quartile of
population)
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| Glucose intolerance |
Impaired glucose
regulation or diabetes |
Fasting glucose
≥6.1
mmol/L
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Fasting glucose
≥110 mg/dL |
Fasting glucose
≥5.6
mmol/L or previous diagnosis of impaired glucose
tolerance or diabetes |
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Hyper insulinaemia
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Fasting
hyperinsulinaemia
(highest quartile of
population) |
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Increased
triglyceride
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TG >150 mg/dL |
TG >2 mmol/L |
TG ≥150 mg/dL |
TG ≥ 1.7 mmol/L |
| Decreased HDLc |
HDL<35 mg/dL (men)
<39 mg/dL (women)
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HDL < 1 mmol/L or
on treatment |
HDL< 40 mg/dL (men)
<50 mg/dL (women)
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HDL
<1.04 mmol/L=men
<1.29 mmol/L=women
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| Hypertension |
Blood pressure
≥140/ 90
Central obesity:
Waist:hip ratio
>0.9 (men)
>0.85 (women)
and/or BMI>30 kg/m2
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Blood pressure
≥140/ 90
or on treatment
Central obesity:
Waist circumference
>94 cm (men)
>80 cm (women)
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Blood pressure
≥130/
≥85 mmHg
Abdominal obesity:
Waist circumference
>102 cm (men)
>88 cm (women)
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Blood pressure ≥
130 SBP or ≥ 85 DBP or treatment
Central obesity:
Waist circumference
>94 cm (European men)
>90 cm (Asian men)
>80 cm (women)
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How common is metabolic syndrome?
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Most studies have used the ATP III definition of the
syndrome, some with modifications to the criteria. Some
studies have used the WHO criteria and some have used
other criteria. Many that have used the WHO criteria
have not performed clamps and thus just use fasting or 2
h post challenge glucose values.
The studies have also looked at different age ranges of
individuals studied. This makes comparison of studies
difficult. However, most European studies have found the
prevalence of the metabolic syndrome to be between 12%
and 25%. (6-9) Studies in North America and Australia
have found a similar prevalence (10-12) while studies in
Asia have mostly found a lower prevalence of 5% to
16%.(13-15)
We have recently used data-sets employed to derive the
current global diabetes prevalence (16) to estimate
global metabolic syndrome prevalence for adults >20
years. We estimate that the current global prevalence of
the metabolic syndrome is approximately 16% (95% CIs
10-23).(17) |
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Reference List
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- Ridker PM, Buring JE, Cook NR, Rifai N.
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- Gupta A, Gupta R, Sarna M, Rastogi S, Gupta VP,
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