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Comparison of Different Definitions of the Metabolic Syndrome in Relation to Cardiovascular Mortality in European Men and Women
The DECODE Study Group; Qiao Q. Diabetologia. 2006;49:2837-2846.
Several different
definitions of the metabolic syndrome have been proposed by various
organizations. Individuals with metabolic syndrome are thought to be at higher
risk of mortality due to cardiovascular disease (CVD). However, it is unclear
whether a diagnosis of metabolic syndrome places an individual at any higher
risk of CVD than the underlying parameters of the definition. This paper
determined the prevalence of the metabolic syndrome by 4 different definitions
and the corresponding risk of CVD, non-CVD, and all-cause mortality.
The 4 sets
of criteria included those established by the World Health Organization (WHO),
the US National Cholesterol Education Program (NCEP), the revised NCEP criteria
(NCEP-R), and the International Diabetes Federation (IDF). Definitions of the
metabolic syndrome as used in this study are given in Table 1.
Table 1. Metabolic
syndrome definitions and criteria
|
Criteria
|
WHO
|
NCEP
|
NCEP-R
|
IDF
|
|
Definition
|
IGT and at least 2 additional criteria
|
Any 3 of 5 criteria
|
Any 3 of 5 criteria
|
Central
obesity (WC) and at least 2
additional criteria
|
|
IGT
|
FPG≥110
mg/dL and/or 2hPG≥140 mg/dL and/or insulin resistance
|
FPG≥110
mg/dL
|
FPG≥100
mg/dL
|
FPG≥100
mg/dL
|
|
Obesity
|
BMI>30
kg/m2 or
WHR>0.90
(males),
WHR>0.85
(females)
|
WC>102
cm (males), WC>88 cm (females)
|
WC>102
cm (males), WC>88 cm (females)
|
WC>94
cm (males), WC>80 cm (females)
|
|
BP
|
BP≥140/90
mm Hg or taking antihypertensive medication
|
BP≥130/85
mm Hg or taking antihypertensive medication
|
BP≥130/85
mm Hg or taking antihypertensive medication
|
Systolic
BP≥130 or diastolic BP≥85 mm Hg
|
|
Dyslipidemia
criterion 1
|
TAG≥1.7
mmol/L and/or HDL <0.9 mmol/L (males), HDL <1.0 mmol/L (females)
|
TAG≥1.7
mmol/L
|
TAG≥1.7
mmol/L
|
TAG≥1.7
mmol/L
|
|
Dyslipidemia
criterion 2
|
N/A
|
HDL
<1.03 mmol/L (males), HDL <1.29 mmol/L (females)
|
HDL
<1.03 mmol/L (males), HDL <1.29 mmol/L (females)
|
HDL
<1.03 mmol/L (males), HDL <1.29 mmol/L (females)
|
IGT =
impaired glucose tolerance; FPG = fasting plasma glucose; 2hPG = 2-hour oral
glucose tolerance test result using 75 g load; BMI = body mass index; WHR =
waist-hip ratio; BP = blood pressure; IFG = impaired fasting glucose; TAG =
triacylglycerol; WC = waist circumference; N/A = not applicable
A total of
10,269 patients from 9 cohorts of 7 studies participating in the Diabetes
Epidemiology: Collaborative Analysis of Diagnostic Criteria in Europe (DECODE)
study formed the study population. The mean age of the patients was 56 years
(range: 30-88 years), 45.9% of patients were male, and the maximum duration of
follow up between studies ranged from 6.6 to 16 years.
The
prevalence of metabolic syndrome within the DECODE cohort varied by definition
and by gender, ranging from 25.9% to 35.9% for males and 19.7% to 34.1% for
women, with the IDF definition yielding the highest prevalence. Considerable
discrepancies in which individuals were classified as having metabolic syndrome
were noted between definitions. Of the 2,116 males satisfying the criteria for
any of 3 definitions for metabolic syndrome (WHO, IDF, and NCEP), only 707
(33.5%) satisfied all 3. Likewise, of 2,096 females satisfying the criteria of
any of the 3 definitions, only 793 (37.8%) satisfied all 3.
The total
number of deaths was 896, with 535 non-CVD deaths and 299 CVD-related deaths.
The cause of death could not be determined in 62 cases.
In males,
all definitions of the metabolic syndrome were associated with increased
CVD-related mortality, with the WHO definition yielding the highest Cox
proportional hazard ratio (HR) (HR range: 1.51-2.09), but the strongest risk
factor was hypertension (blood pressure ≥130/85 mm Hg or taking antihypertensive
medication), with a multivariate adjusted HR of 2.30. BP ≥140/90 mm Hg (or
treated) had a multivariate adjusted HR of 2.04. The strongest risk factors for
non-CVD mortality in males were BMI>30 kg/m2 or WHR>0.90 (HR =
1.50), BP ≥140/90 mm Hg (or treated) (HR = 1.42), BP ≥130/85 mm Hg
(or treated) (HR = 1.31), and FPG≥110 mg/dL (HR = 1.31). Non-CVD deaths
were not correlated with any definition of the metabolic syndrome (HR range:
1.02-1.25). The strongest risk factors for all-cause mortality in males were BP
≥140/90 mm Hg (or treated) (HR = 1.60), BP ≥130/85 mm Hg (or
treated) (HR = 1.57), satisfaction of the WHO criteria for metabolic syndrome
(HR = 1.57), and BMI>30 kg/m2 or WHR>0.90 (HR = 1.50).
In females,
the association between the different definitions of the metabolic syndrome and
CVD-related mortality was weaker (HR range: 1.09-1.60). The strongest risk
factor for CVD-related mortality was hypertension (BP ≥130/85 mm Hg or
taking antihypertensive medication), with a multivariate adjusted HR of 2.31. BP ≥140/90 mm Hg had a multivariate adjusted HR of 2.07.
FPG≥110 mg/dL had a multivariate adjusted HR of 2.17. The strongest risk
factors for non-CVD mortality in females were FPG≥110 mg/dL (HR = 1.41),
BMI>30 kg/m2 or WHR>0.85 (HR = 1.34), and WC>88 cm (HR =
1.27). Non-CVD deaths were not correlated with any definition of the metabolic
syndrome (HR range: 1.05-1.09). The strongest risk factors for all-cause
mortality in females were FPG≥110 mg/dL or 2hPG ≥140 mg/dL (HR =
1.50), FPG≥110 mg/dL (HR = 1.40), and BMI>30 kg/m2 or
WHR>0.85 (HR = 1.33).
These
findings suggest that the current definitions of the metabolic syndrome have
limited utility in predicting mortality relative to conventional univariate or
multivariate cardiovascular risk factor assessment.
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