Original Article#
Comparison of Definitions of the Metabolic Syndrome
in Adult Asian Indians
JS Wasir*, A Misra*, NK Vikram**, RM Pandey***, R Gupta****
Abstract
Objective: The optimum definition of the metabolic syndrome (MS) is not known. We compared international
definitions of MS [recently proposed modified definition of National Cholesterol Education Programme,
Adult Treatment Panel III (NCEP, ATP III) and International Diabetes Federation (IDF)] with two proposed
candidate definitions in adult Asian Indians.
Design: Data from three previous cross-sectional studies carried out in North India were analyzed.
Subjects: The study included 2050 adult (mean age: 40 ± 18 years) Asian Indian subjects residing two
metropolitan cities.
Measurements : Candidate definitions of MS were proposed by modifying the NCEP, ATP III and IDF
definitions by including the following modified variables into two combinations (MS-ATP1 and MS-IDF1);
waist circumference cut-off points as >90 cm in males and >80 cm in females, body mass index (BMI) cutoff point as >23 kg/m2, impaired fasting glucose (IFG) cut-off point >100 mg/dl and waist circumference
as an obligatory criterion.
Results: Maximum overall and gender-specific prevalence of the MS (49.2% overall; 41.4% in males; 55.3% in
females) was observed using the definition which included modified cut-off points of WC (non-obligatory),
BMI, and IFG (>100 mg/dl) in addition to other defining parameters. Compared to other definitions this
proposed candidate definition maximally detected presence of MS in subjects with IFG and T2DM [Percentage
prevalence: 78.1% (73.0-82.7) and 91.1% (84.2-95.6)]. Even in subjects without abdominal obesity, a high
prevalence of other abnormal defining parameters of the metabolic syndrome; hypertension (≥ 130 or ≥ 85
mmHg), 35.7%; BMI > 23 kg/m2, 15.3%; hypertriglyceridemia (>150 mg/dl), 20.2% and low levels of HDL-C
(< 40 in males; <50 mg/dl in females), 55% were seen. Further, 10.5% of subjects who did not have abdominal
obesity had presence of at least 3 risk variables of the metabolic syndrome. These data indicate that by making
abdominal obesity a mandatory criterion would lead to missing of some cases of the metabolic syndrome.
Conclusion: By including BMI and making waist circumference as a non-obligatory criterion, more cases of
the metabolic syndrome is detected. For Asian Indians, making waist circumference as mandatory variable
in the definition of the metabolic syndrome would lead to non-inclusion of nearly 11% cases who would
otherwise be diagnosed as metabolic syndrome according to modified NCEP, ATP III definition. ©
I
Introduction
nsulin resistance has been implicated as the central
process in pathogenesis of type 2 diabetes mellitus
(T2DM) and cardiovascular disease (CVD). Keeping
this concept centrally, the World Health Organization
(WHO) in 1998 proposed the first formal definition for
*Department of Diabetes and Metabolic Diseases, Fortis
Hospitals, New Delhi, 110070, India. **Department of Medicine;
***Biostatistics, All India Institute of Medical Sciences, New Delhi110029, India. ****Department of Medicine, Monilek Hospital and
Research Centre, Jawahar Nagar, Jaipur 302004, India.
#Rapid Publication
Received : 18.10.2007; Accepted : 28.12.2007
158
the insulin resistance syndrome. This definition required
biochemical measurement of insulin resistance as an
obligatory criterion.1 In 2001 the National Cholesterol
Education Programme, Adult Treatment Panel III (NCEP,
ATP III) introduced a clinical definition of the metabolic
syndrome. The definition was based on the premise
that clustering of ‘lipid and non-lipid’ parameters in
an individual increased future risk of development
of type T2DM and CVD.2 Further, other definitions of
the metabolic syndrome have been formulated and
evaluated for their adequacy for predicting presence of,
or the future risk of T2DM and/or CVD.3-5
Investigators have reported conflicting observations
regarding aptness of various definitions of the metabolic
syndrome to detect the presence of insulin resistance or to
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© JAPI • VOL. 56 • MARCH 2008
correctly predict future risk of CVD or T2DM.6,7 Further,
the applicability of NCEP, ATP III definition to various
ethnic groups has been doubted3,8,9 particularly for south
Asians who have comparatively lower body mass index
(BMI), excess body fat, truncal and abdominal adiposity,
lower waist circumference (WC), and reported to have
higher magnitude of insulin resistance and risk for
T2DM and CVD than white Caucasians.10 Specifically,
waist circumference as defined by the NCEP, ATP III
cut-off points underestimates prevalence of abdominal
obesity in adult Asians,3 and recently we have further
strengthened the data by providing waist circumference
action levels for adult Asian Indians, which are lower
than the presently accepted international accepted cutoff points for defining abdominal obesity.11 Further, we
have recently shown that the NCEP, ATP III definition
underestimates prevalence of the metabolic syndrome
and, in particular, is poor in identification of the
metabolic syndrome in adult Asian Indian subjects
with T2DM. 8 Moreover, we have proposed that a
candidate definition of the metabolic syndrome which
included, in addition to other NCEP, ATP III definition
parameters, modified ethnic specific cut-off points
for; body mass index (BMI), waist circumference and
a measure of truncal subcutaneous fat (subscapular
skinfold thickness), best identified the metabolic
syndrome in subjects with impaired fasting glucose
(IFG) and T2DM.8 In line with our observations8 and
those from other investigators,3,9,12 the American Heart
Association/National Heart, Lung, and Blood Institute in their latest scientific statement13 have recommended
using the NCEP, ATP III definition with lower cut-off
point for defining abdominal obesity for ethnic groups
who are more insulin resistance and prone to develop
T2DM and also lower cut-off point for diagnosis of IFG
(>100 mg/dl) (termed as MS-ATP in the current study). The definition of the metabolic syndrome in adults,
therefore, continues to be modified. Finally, according
to results of our recent study, optimization of definition
of the metabolic syndrome is also needed for adolescent
Asian Indians.14,15
Realizing the need for a universally acceptable and
easy-to-use definition of the metabolic syndrome, which
may be utilized for research and clinical purpose and
also for international comparisons, the International
Diabetes Federation (IDF) proposed a new definition
of the metabolic syndrome. 16 The changes in this
definition as compared to NCEP, ATP III definition2
included; abdominal obesity is an obligatory criterion,
ethnic-specific cut-off points of waist circumference,
and a lower cut-off point (>100 mg/dl) of fasting blood
glucose. Some perceived shortcomings of the NCEP,
ATP III definition have been corrected by the IDF
definition However, the IDF definition has not been
tested in epidemiological studies, compared against
other definitions of the metabolic syndrome, and tested
in various ethnic groups, specifically Asian Indians.
© JAPI • VOL. 56 • MARCH 2008
We hypothesized that in adult Asian Indians the IDF
definition would identify the metabolic syndrome better
in subjects with IFG and T2DM as compared to the NCEP,
ATP III definition, and candidate definitions proposed
by us. In present study, we tested the recently proposed
modified definition of NCEP, ATP III, IDF definition, and
two candidate definitions of the metabolic syndrome in
an adult population sample from North India. Materials and methods
Study design and sampling method
F o r t h e c u r re n t a n a l y s i s d a t a f ro m t h re e
epidemiological, population-based studies carried
out between 1998 to 2003 in two metropolitan cities in
North India by two investigation teams, were analyzed.
Approval was taken from respective institutional
review boards. The methodology and field procedures
are described in detail elsewhere.17 Briefly, two studies
were conducted in New Delhi by our group (AM,
NKV); the first on urban adult population18 and the
second on young subjects aged 14-25 years.19 The third
study, Jaipur Heart Watch-2 (JHW-2) was conducted by
another investigator (RG) in the city of Jaipur located
in Northwest state of Rajasthan, nearly 250 kilometers
from New Delhi.20 In these studies, random selection of
subjects was carried out as described previously.18,20 An
informed consent was obtained from all subjects. For
the present study, data from the subjects older than 18
years of age have been analyzed.
Clinical profile and measurements
The data of blood pressure measurement and
anthropometric parameters (height, weight, waist and
hip circumferences) were available for all subjects. Field
procedures including blood pressure measurement and
anthropometry were the same in all the studies, and
were carried out by a single trained observer at each
site of study. Blood pressure was measured in the right
arm with the subject seated and rested for 5 minutes
using a standard mercury sphygmomanometer. At least
two readings at 5-minute intervals were taken and if an
abnormal value was obtained, then another reading was
taken after 30 minutes of rest. Waist circumference was
measured midway between the iliac crest and the lower
most margin of the ribs with bare belly and at the end
of normal expiration.21
Biochemical measurements
Fasting blood glucose (FBG) levels and lipid profile
[Total cholesterol (TC), serum triglycerides (TG) and
high-density lipoprotein cholesterol (HDL-c)] were
estimated within 48 hours of collection according
to previously described methods. 22 Low-density
lipoprotein cholesterol (LDL-c) levels were calculated
using the Friedewald’s formula.23
Definitions
A. Definitions of the metabolic syndrome: The
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159
following is a brief description of the various
definitions (see Table 1 for complete description):
1. Recently proposed modified definition of
NCEP, ATP III 13 (MS-ATP) and IDF (MSIDF)16 definitions were set as reference for
comparison.
2. M S - AT P d e f i n i t i o n w a s m o d i f i e d b y
incorporating BMI to generate a modified
definition (MS-ATP1).
3. IDF (MS-IDF) definition was modified by
addition of BMI as a defining parameter in
addition to the proposed parameters to generate
the definition MS-IDF1.
4. MS-ATP and MS-IDF definitions of the
metabolic syndrome are similar to each other
in all ways except one i.e. waist circumference
is obligatory in the MS-IDF definition and nonobligatory in the MS-ATP definition.
5. The two candidate definitions proposed by
us include BMI (>23 kg/m2) as an additional
defining parameter (MS-ATP1, and MS-IDF
1).
6. The metabolic syndrome was identified
according to the following:
a. Three or more defining parameters were
abnormal (MS-ATP, MS-ATP1), or
b. Along with presence of abnormal obligatory
criterion, presence of two other criteria (MS IDF and MS-IDF1).
B. Blood glucose levels were classified as following:16
1. Normoglycemia: <100 mg/dl
2. Impaired fasting glucose (IFG): 100 to 125 mg/
dl
3. T2DM: ³ 126 mg/dl
Statistical analysis
Data were recorded on a pre-designed performa
and managed on MS Excel worksheet. The statistical
analysis was done in three parts. First, we compared
the recently proposed modification of the NCEP, ATP III
(MS-ATP) and IDF (MS-IDF) definitions of the metabolic
syndrome to determine if waist circumference should
be used as an obligatory criterion. Secondly, the IDF
(MS-IDF) and modified IDF (MS-IDF1) were used to
determine the importance of BMI as a defining parameter
of the metabolic syndrome. Finally, the two candidate
definitions of the metabolic syndrome were compared
with each other and also with MS-ATP and MS-IDF
definition of the metabolic syndrome by computing
the percentage prevalence and 95% confidence interval.
Further, we applied all the definitions to three subgroups
(normoglycemia, IFG and T2DM). The prevalence of
the metabolic syndrome was compared overall and in
subgroups. STATA 8.0 statistical software was used for
data analysis. Results
The study included clinical and biochemical details
of 2050 subjects. The mean age was 40 ± 18 years. The
average values and prevalence of measures of obesity,
and surrogate markers of insulin resistance are shown
in Table 2. All the measures of obesity (except abnormal
BMI) were more prevalent in females than males (Table
2). The prevalence of abdominal obesity (high waist
circumference) increased by 21.7% (17.6% versus 39.3%)
and 9.1% (39.3% vs. 48.4%) by decreasing the waist
circumference cut-off points to >90cm and >80cm in
males and females, respectively. Overall abdominal
obesity was more prevalent in females (Table 2). The
prevalence of IFG increased from 11.7% to 15.9% and
10.4% to 16.3% in males and females, respectively on
using the recently proposed cut-point for IFG16 (Table
2).
Table 3 depicts the overall and gender-specific
percentage prevalence of the metabolic syndrome using
various definitions. The recently proposed modified
definition of NCEP, ATP III (MS-ATP) detected the
metabolic syndrome in 34.1% (31.9-36.3) [25.5 % (22.528.6) and 40.7 % (37.7-43.7) in males and females,
respectively]. This definition (MS-ATP) in which waist
Table 1 : Rationale and components of various definitions of the metabolic syndrome
Metabolic
Syndrome
Definitions(MS)
Blood pressure
(mm Hg)
≥ 130/≥ 85
Triglycerides
(mg/dl)
≥ 150
Fasting Blood
Glucose (mg/dl)
≥ 100
HDL-C (mg/dl)
M <40 , F <50
Waist
circumference(cm)
Males: >90 Females: >80
Body mass
index (kg/m2)
≥ 23
Definitions of the metabolic syndrome with obligatory waist circumference and non-obligatory BMI as an additional defining parameters
MS-IDF ‡j,ψ +
+
+
+
+
MS-IDF1ψ
+
+
+
+
+
+
Definitions of the metabolic syndrome with non-obligatory waist circumference and BMI as an additional defining parameters
MS-ATP¶,†
+
+
+
+
+
+
+
+
+
+
+
MS-ATP1¶
Candidate definitions of the metabolic syndrome: MS-ATP1 and MS-IDF1; ‡j , International Diabetes Federation definition of the metabolic
syndrome;16 ψ, Presence of abdominal obesity (waist circumference) is obligatory, and presence of two other abnormal criteria required for
diagnosis of the metabolic syndrome[16]; †, Same as the newly proposed (AHA/NHLBI) modification of the NCEP, ATP III definition of the
metabolic syndrome;13 ¶, Presence of three or more abnormal criteria required for diagnosis of the metabolic syndrome (waist circumference
non-obligatory).
160
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© JAPI • VOL. 56 • MARCH 2008
Table 2 : Measures of obesity and prevalence of surrogate markers of the metabolic syndrome
Variables
Average measures of obesity: [Mean ± sd]
Waist circumference (cm)
Body mass index (kg/m2) Prevalence of measures of obesity: [% (95% confidence interval)]
Waist circumference (M:> 102 cm, F: > 88 cm)
Modified waist circumference (M: > 90 cm, F:> 80 cm)
Body mass index (> 23 kg/m2)
Surrogate markers of insulin resistance: [% (n)]
Impaired fasting glucose (FBG ≥ 110 mg/dl <126 mg/dl)*
Impaired fasting glucose (FBG ≥ 100 mg/dl < 126 mg/dl)**
Diabetes mellitus (FBG ≥ 126 mg/dl)
High blood pressure (Blood pressure ≥ 130/≥ 85 mm Hg) Hypertriglyceridemia (Serum triglycerides ≥ 150 mg/dl)
Low levels of HDL-C (M: < 40 mg/dl, F: < 50 mg/dl)
n
Males
n
Females
866
881
85.6±15.3
22.8±5.2
1125
1165
79.7±14.3
23.0±5.7
866
866
881
17.6(15.1-20.3)
39.3(36.0-42.6)
47.0 (43.7-50.3)
1125
1165
1165
28.9(26.3-31.6)
48.4(43.8-49.6)
44.0(41.2-46.9)
847
847
847
883
879
874
11.7(99)
15.9(135)
6.4(54)
29.1(257)
28.9(254)
43.8(383)
1156
1156
1156
1167
1134
1127
10.4(120)
16.3 (187)
5.5(63)
42.8(499)
25.5(289)
81.8(922)
M - males; F - females; FBG - fasting blood glucose; HDL-C - high-density lipoprotein cholesterol; *,previous ADA criteria for diagnosis of IFG;
**,recently proposed criterion for IFG.34
Table 3 : Overall and gender-specific percentage prevalence of the metabolic syndrome
Metabolic Syndrome
Definitions (MS)
Overall
; % prevalence (95% CI)
n
Males
Females
Definitions of the metabolic syndrome with obligatory waist circumference and non-obligatory BMI as an additional defining parameters
2050;
25.3
(23.4-27.2)
883;
19.5
(16.9-22.2)
1167;
29.7
(27.0-32.4)
MS-IDF‡
MS-IDF1
2050;
41.4
(39.2-43.5)
883;
36.8
(33.6-40.1)
1167;
44.8
(41.9-47.7)
Definitions of the metabolic syndrome with obligatory waist circumference non-obligatory and BMI as an additional defining parameters
1896;
34.1
(31.9-36.3)
821;
25.5
(22.5-28.6)
1075;
40.7
(37.7-43.7)
MS-ATP¶
MS-ATP1
1892;
49.2
(47.0-51.5)
819;
41.4
(38.0-44.9)
1073;
55.3
(52.2-58.3)
‡
- IDF definition of the metabolic syndrome;16 ¶ - recent modification NCEP, ATP III definition of the metabolic syndrome.13
circumference was a non-obligatory criterion detected
the metabolic syndrome more as compared to the
original IDF (MS-IDF; waist circumference obligatory)
definition [MS-ATP vs. MS-IDF: 34.1% (31.9-36.3) vs.
25.3% (23.4-27.2)]. By addition of BMI as a defining
criterion the metabolic syndrome was identified more
by the definition MS-IDF1 as compared to MS-IDF in the
entire study population as well as in sub groups (Table 3
and 4). Maximum overall and gender specific prevalence
of the metabolic syndrome was observed by applying
the definition MS-ATP1 [49.2% (47.0-51.5) overall; 41.4%
(38.0-44.9) in males; 55.3% (52.2-58.3) in females].
Table 4 shows the percentage prevalence (overall and
gender-specific) in the study population according to
the glycaemic status. MS-ATP detected the metabolic
syndrome in 22.3 % (20.2-24.5), 73.2% (67.7-78.1) and
86.6% (78.9-92.3) of subjects with normoglycemia, IFG
and T2DM. Amongst the various definitions, candidate
definition MS-ATP1 maximally detected presence of the
metabolic syndrome overall as well as in subgroups
(40.3 % (37.8-42.9), 78.1% (73.0-82.7) and 91.1% (84.295.6) in subjects with normoglycemia, IFG and T2DM,
respectively. Importantly, 10.5% of subjects with normal
waist circumference had three cardiovascular risk
factors.
Discussion
© JAPI • VOL. 56 • MARCH 2008
We present for the first time, comparison of recently
proposed (NCEP, ATPIII and IDF) definitions, and
two modified candidate definitions of the metabolic
syndrome in adult Asian Indians. This analysis is
important, since we are yet to determine the optimal
definition of the metabolic syndrome, specifically for
South Asians.
NCEP, ATP III definition provided, for the first time,
simple criteria for detection of the metabolic syndrome
which could be easily used in most settings, even in the
developing countries. Although it was widely used,
several lacunae have been pointed out.6,7 The most
important lacuna, from point of view of South Asians,
is cut-off points of the waist circumference.24,25 The
IDF definition of the metabolic syndrome includes all
the components of the NCEP, ATP III definition with
some modifications.16 Although abdominal obesity is
an important criterion of the metabolic syndrome, it is
not clear why it should be made mandatory in the IDF
definition. For example, insulin resistance and other
components of the metabolic syndrome may occur in
people who do not have abdominal obesity, or are nonobese (BMI < 25 kg/m2).26 Particularly in the developing
countries, non-obese people or those without abdominal
obesity may develop insulin resistance, IFG, and
T2DM. 26 To analyze whether obligatory criterion
of abdominal obesity would make any significant
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161
Table 4 : Prevalence of the metabolic syndrome by various definitions according to glycaemic status
Metabolic Syndrome
Waist BMI >23 kg/m2
Definitions (MS)
circumference
Obligatory
(M; >90cm: F; >80cm)
Normoglycemic
FPG <100 mg/dl
Impaired Fasting Glucose
FPG 100-125 mg/dl
Overall [n; % prevalence (95% CI)]
+
-
1567; 17.4 (15.5-19.4) 322; 49.7 (44.1-55.3)
MS-IDF‡
MS-IDF1
+
+
1564; 37.7 (35.3-40.2) 322; 53.4 (47.8-56.9)
MS-ATP¶
-
-
1486; 22.3 (20.2-24.5) 298; 73.2 (67.7-78.1)
MS-ATP1
-
+
1483; 40.3 (37.8-42.9) 297; 78.1 (73.0-82.7)
Males [n; % prevalence
(95% CI)]
MS-IDF‡
+
-
658; 11.9 (9.5-14.6)
135; 40.0 (31.7-48.8)
MS-IDF1
+
+
658; 33.7 (30.1-37.5) 135; 46.7
(60.3-85.0)
MS-ATP¶
-
-
639; 14.2 (11.6-17.2) 131; 58.2 (49.1-66.6)
MS-ATP1
-
+
638; 32.5 (28.8-36.2) 130; 66.2 (57.3-74.2)
Females [n; % prevalence
(95% CI)]
MS-IDF‡
+
-
906; 21.4 (18.8-24.9)
187; 56.7 (49.3-63.9)
MS-IDF1
+
+
906; 40.6 (37.4-43.9) 187; 58.3
(60.3-83.4)
MS-ATP¶
-
-
847; 28.3 (25.3-31.5) 167; 85.0 (78.7-90.1)
MS-ATP1
-
+
845; 46.3 (42.9-49.7) 167; 87.4 (81.4-92.0)
Type 2
Diabetes Mellituse
≥ 126 mg/dl
117;
117;
112;
112;
73.5
73.5
86.6
91.1
(64.5-81.2)
(64.5-81.2)
(78.9-92.3)
(84.2-95.6)
54; 74.1 (60.3-85.0)
(38.0-55.4) 54; 74.1
51;
51;
82.4 (69.1-91.6)
90.1 (78.6-96.7)
63; 73.0 (60.3-83.4)
(50.9-65.4) 63; 73.0
61;
61;
90.2 (79.8-96.3)
91.8 (81.9-97.3)
, IDF definition of the metabolic syndrome: presence of obligatory criteria (waist circumference) along with presence of two or more abnormal
criteria required for diagnosis of metabolic syndrome;16 ¶, recently modified NCEP, ATP III definition of the metabolic syndrome: presence
of three or more abnormal criteria required for diagnosis of the metabolic syndrome;13 ‘+’, parameter included; ‘-‘, parameter not included;
‡
difference in identification of the metabolic syndrome
in the study population or in subgroups, we tested a
recently modified NCEP, ATP III13 (MS-ATP) definition in
which presence of abdominal obesity is non-mandatory
criterion against the IDF definition (MS-IDF; waist
circumference an obligatory criterion). Interestingly,
this definition (MS-ATP) better detected presence of
the metabolic syndrome overall, in either gender and
also in subgroups according to glycemia (Tables 3 and
4). Overall, it appears that making abdominal obesity
as mandatory criterion may not improve identification
of other risk clusters in subjects with T2DM or IFG, and
hence may not be an appropriate option. In particular,
persons having other components of the metabolic
syndrome but not having abdominal obesity would
not be identified by IDF definition but may still be
at a greater future risk of T2DM or CVD by virtue of
having clustering of other risk factors. For example,
in the present study we observed that even in subjects
without abdominal obesity (i.e. waist circumference
<90 cm or < 80 cm in males and females, respectively)
there was a high prevalence of other abnormal defining
parameters of the metabolic syndrome; hypertension
(e”130 or e”85 mmHg), 35.7%; BMI > 23 kg/m2, 15.3%;
hypertriglyceridemia (>150 mg/dl), 20.2% and low
levels of HDL-C (< 40 in males; <50 mg/dl in females),
55%. Our data indicated that 10.5% of subjects who did
not have abdominal obesity had presence of at least 3
cardiovascular risk factors, hence these subjects would
not be diagnosed to be having metabolic syndrome
despite having substantial cardiovascular risk. Similarly,
in a recent investigation we had shown that ~30%
Asian Indian adolescents with normal BMI and waist
162
circumference had hyperinsulinemia and would not
be identified by appropriate (percentile-based) IDF
definition of the metabolic syndrome.14
The relative importance of BMI, or waist circumference
or both27 as predictor(s) of cardiovascular risk factors,28,29
and whether one or both should be included in
definition of the metabolic syndrome continue to be
debatable issues. The BMI has been included in the
WHO definition,30 and other modified definitions8,31 of
the metabolic syndrome. Also, lower cut-off point of
BMI (23 kg/m2) should be considered for Asians1,10,32,33
if it is included as a defining variable of the metabolic
syndrome. 8 In the present investigation we have
demonstrated that by addition of BMI (MS-IDF1 and
MS-ATP1) the percentage prevalence of the metabolic
syndrome increased from 25.3% and 34.1% (MS-IDF/
MS-ATP) to 41.4% and 49.2% (MS-IDF1/MS-ATP1).
Hence it may be worthwhile including BMI as an
additional defining parameter in the definition of the
metabolic syndrome.
Importantly, including ethnic-specific cut-off point of
waist circumference and a lowered cut-off point of fasting
blood glucose are evidence-based amendments.11,34
Furthermore, with these modifications, IDF definition
appears to be applicable across most ethnic groups,
particularly for Asian populations. However, despite
these modifications, IDF definition detects the metabolic
syndrome less in comparison to other candidate
definitions for Asian Indians proposed by us in the
current study (Table 3 and 4). Upon comparison of the
various definitions, we observed that the candidate
definition MS-ATP1 (included: modified cut-off points
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© JAPI • VOL. 56 • MARCH 2008
for waist circumference and fasting blood glucose,
modified cut-off point of BMI along with other criteria of
NCEP, ATP III definition, all non-mandatory) identified
presence of the metabolic syndrome in subjects with
IFG and T2DM more than other definitions including
the NCEP, ATP III and IDF definitions (Table 4). But,
whether this candidate definition is optimal or can be
applied easily to the general population including white
Caucasians remains to be investigated.
The recent studies comparing the various definitions
of the metabolic syndrome in Asians indicate a
conflicting evidence of the NCEP, ATP III (modified for
Asian Indians) and WHO definition when compared to
the IDF definition. In a nationally representative sample
of ~ 16,000 Chinese adults MS was detected in 16.5 %
and 23.3% (% agreement between the definitions, 93.2%)
using the IDF and NCEP, ATPIII definitions respectively.
Further, when compared to IDF definition the ATP III
definition detected aggregation of cardiovascular risk
factors better.35 Further, in a multi-ethnic population
including South Asians, agreement between the two
definitions was gender specific with greater % agreement
(~80%) in females as compared to males. 36 When
compared to the modified NCEP/ATP III definition
the IDF definition is associated with the highest risk for
detection of extensive CAD on angiography (OR 2.83; p=
0.0190). In another study, carotid atherosclerosis has been
shown to be best associated with MS as defined by the
WHO definition when compared with other definitions
of MS including the IDF definition.37 Interestingly, in
Caucasian subjects with T2DM the prognostic accuracy
of the IDF definition for all cause mortality is markedly
reduced when compared to the modified NCEP, ATP
III definition.38 Finally, even though the IDF definition
better detected prevalence of MS in Korean subjects, but
when compared to the NCEP, ATP III definition the odds
ratio for detection of CAD were lower (NCEP, ATP III
Vs IDF: 2.8 Vs 3.5).39
On further analysis of a recently reported study on
the metabolic syndrome by our group,14 we noted that
~80% of adolescent Asian Indian with normal BMI
and waist circumference but increased subscapular
skinfold thickness had fasting hyperinsulinemia. That
subscapular adipose tissue is thicker, and more closely
correlated with insulin resistance in Asian Indians
was shown by several groups including ours.40-42 A
new candidate definition of the metabolic syndrome
for adult Asian Indians in which subscapular skinfold
thickness (cut-off point: >18 mm) was included as a
new defining parameter was shown by us to perform
better than the NCEP, ATP III definition.8 Interestingly,
on sub-group analysis of the present study data we
found that 22.6% (n=196) of adult Asian Indians had
increased subscapular skinfold thickness (> 18 mm)
but normal BMI and waist circumference (results not
shown). To summarize, though preliminary, these
data suggest that subscapular subcutaneous skinfold
© JAPI • VOL. 56 • MARCH 2008
thickness (or skinfold at other truncal sites) may be
strongly correlated to insulin resistance in Asian Indians
warranting inclusion of this parameter in any new
definitions and risk scoring of the metabolic syndrome
or T2DM.
Insulin resistance has been considered as the central
factor and an important pathogenic mechanism for the
metabolic syndrome. Further, the primary therapeutic
intervention for the metabolic syndrome may also be
directed towards control of insulin resistance.43 Doubts
have been raised as to the adequacy of the NCEP, ATP III
definition of the metabolic syndrome to detect presence
of insulin resistance.6 Such evaluation for IDF definition
remains to be done.
As yet, definitions of the metabolic syndrome
are unsatisfactory, but encouragingly evolving. To
determine a correct and universally applicable definition
of the metabolic syndrome, the international agencies
(NCEP, IDF, WHO and others) should initiate large,
prospective studies involving several ethnic groups
to test various candidate definitions against insulin
resistance risk, CVD, T2DM and overall mortality.
Acknowledgments
This study was partially supported by a grant from
the Science and Society Division, Department of Science
and Technology, Ministry of Science and Technology,
Government of India and by an unrestricted grant from
Monilek Hospital and Research Centre, Jaipur, India.
Mr Ramesh Giri assisted in anthropometry and body
fat measurement, Mr Inder Taneja, Mr Gian Chand and
Mrs Alice Jacob performed biochemical investigations.
The cooperation of the subjects who took part in the
study is greatly appreciated.
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© JAPI • VOL. 56 • MARCH 2008