CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 6, November/December 2011
AFRICA
295
Editorial
The metabolic syndrome: a definition dilemma
ARNAB GHOSH
The metabolic syndrome (MS) is a common phenotype asso-
ciated with an increased risk for type 2 diabetes mellitus
(T2DM) and cardiovascular disease (CVD). Although there is
no universally accepted definition for the MS, affected individu-
als commonly have a cluster of features, including abdominal
obesity, hypertension, dyslipidaemia and dysglycaemia.
1-4
The first formal definition of the MS was proposed by the
World Health Organisation (WHO) in 1999. In the same year,
the European Group for the Study of Insulin Resistance (EGIR)
suggested a similar definition to that of the WHO, but excluded
the microalbuminuria and diabetes components. In 2001, the
United States National Cholesterol Education Program Adult
Treatment Panel (NCEP ATP III) published a more practical
definition for the MS, which eliminated insulin resistance as a
criterion.
1
A few years later, in 2005, the cut-off point for fasting plasma
glucose was lowered, resulting in the modified NCEP ATP
III (modified ATP III) definition.
2
In 2005, the International
Diabetes Federation (IDF) proposed a new definition for the MS,
which made abdominal obesity, classified by ethnic-specific
cut-off points, a necessary condition for the MS. In 2007, the
IDF presented a definition of the MS for use in children and
adolescents, thus becoming the first major organisation to do so.
Throughout the Asia-Pacific region, there are differences in
the prevalence of obesity and metabolic disturbances. People
of Indian origin (PIO) are ethnically a particularly vulnerable
group from the standpoint of metabolic abnormalities.
3
Keeping
this in mind, researchers in the Indian diaspora are now using
South Asian Specific (SAS) cut offs to define the MS in people
of Indian origin.
The SAS definition of the MS is otherwise similar to the modi-
fied ATP III with the exception of cut offs for waist circumfer-
ence (WC) (lower vs modified ATP III) and triglycerides (higher
vs modified ATP III). However, it is noteworthy to mention that
whether using the modified ATP III or SAS definition of the MS,
a large number of individuals may be misclassified due to lack
of a common minimum platform required to better comprehend
the problem in people of Indian origin.
3-5
Although widely used in epidemiological research, there has
been ongoing concern that the WC cut-off points in the modi-
fied ATP III definition, which were predominantly intended for
Americans, might not be appropriate for other ethnic groups,
such as Asian Indians. South Asians (e.g. Asian Indians) have
a more centralised distribution of body fat and a markedly
higher mean waist–hip ratio (WHR) for a given level of body
mass index (BMI) compared to Europeans.
5
In Asian popula-
tions, morbidity and mortality is occurring in people with lower
BMI and smaller WC. Therefore they tend to accumulate intra-
abdominal fat without developing generalised obesity.
4,5
Although the IDF definition of the MS in most instances
failed to identify a subgroup of subjects who had the highest
risk for CVD, before the IDF’s definition of the MS, the effect
of ethnicity on the individual criteria for diagnosing the MS was
not considered. Recently, comparisons of the prevalence of the
MS between different ethnic groups have raised concerns about
the validity of the WHO, NCEP ATP III, modified ATP III and
IDF definitions when applied across different ethnic groups.
The originally accepted criteria for the MS were based on risk
prediction in non-Asian populations.
6
However, recent data from
the Asian population, including Asian Indians, indicate that these
definitions may not be satisfactory for risk prediction.
3
Although genetics most likely plays a crucial role in develop-
ment of the MS, elucidating the exact genes involved has been
hindered by the lack of a consistent definition of the MS,
7
the
varying combination of phenotypes even within a single defini-
tion, ethnic disparities, and gender influences. Recently, a large
body of literature has emerged on early-life origins of the risk for
the MS and associated diseases, such as coronary heart disease
(CHD). Findings that experiences during the individual’s whole
lifetime affect risk for disease highlight the need for an approach
to understanding ethnic differences considering these early
childhood conditions.
Moreover, research on the MS among children and adoles-
cents and the implications of having the MS is limited. Because
the roots of many adult chronic diseases originate in childhood,
establishing a universally agreed definition of the MS in children
and adolescents may help to identify children and adolescents
who are at high risk for developing the MS, and allow for early
prevention of possible adverse health events in early adulthood.
Differences in the prevalence of the MS and its components
using the various definitions, both within and between popula-
tions, indicate that caution is required when comparing studies
from different countries.
7
Determining the clinical significance
of these differences will require prospective outcome studies.
Furthermore, to make the definition of the MS more sensitive,
factors such as family history, habitual physical activity and
smoking, along with region-specific cut offs for individual MS
components are required to better comprehend the MS.
4-7
ARNAB GHOSH, PhD,
Department of Anthropology, Biomedical Research
Laboratory, Visva Bharati University, Sriniketan, West Bengal,
India
References
1.
NCEP. Executive summary of the third report of the National
Cholesterol Education Program (NCEP): expert panel on detection,
evaluation, and treatment of high blood cholesterol in adults (Adult
