The prevalence of metabolic syndrome varies among
different ethnic and racial populations. Blacks in the African Diaspora
continue to have increasing cardiovascular diseases, type 2 diabetes and
associated complications when compared with their white counterparts.
Similarly, Indian Asians and Filipinos have higher rates of diabetes and its
associated CV complications compared with whites.
Although the exact reasons may be multifactorial
(genetic vs. environmental), there are intriguing metabolic and anthropometric
differences in ethnic minorities residing in diverse geographic locations when
compared with whites. During the past three decades, researchers from several
studies have reported metabolic differences in people of the African Diaspora.
Current data have shown that in general, blacks without diabetes are more
insulin resistant and hyperinsulinemic than their white counterparts. Further,
blacks residing in the Western world are more obese than whites. Most
importantly, however, for identical BMI, blacks have lower intra-abdominal
visceral adiposity than their white counterparts. National Health and Nutrition
Examination Survey III data revealed that the presence of metabolic syndrome
was lower in blacks when compared with whites.
The major confounders that account for the ethnic
differences in metabolic syndrome between blacks and whites can be partly
attributed to the higher levels of HDL and corresponding lower serum
triglyceride levels in blacks when compared with whites. This is paradoxical
since a key pivotal lesion purported to underlie metabolic syndrome is insulin
There is increasing controversy regarding whether
conventional CV risk factors are similar among different ethnic groups. Results
of recent studies have demonstrated that the prevalence of metabolic syndrome
is higher in immigrant Indian Asians than in whites and blacks residing in the
United Kingdom. We should note that immigrant Indian Asians residing in the
United Kingdom are, in general, leaner than their white and black counterparts.
However, Indian Asians with similar BMIs have higher visceral adiposity,
greater insulin resistance, severe hypertriglyceridemia and, consequently,
higher prevalence rates of CV risk factors than their European and black
counterparts. Furthermore, researchers have reported that for similar BMI,
Filipino Americans have higher rates of metabolic syndrome, insulin resistance
and greater intra-abdominal visceral adiposity than whites and blacks. The
paradoxical findings of higher obesity rates (BMI >30), greater insulin
resistance and less metabolic syndrome in blacks in contrast with the
higher prevalence of metabolic syndrome in leaner ethnic populations, eg,
Indian Asians and Filipinos with severe insulin resistance calls into
question whether the components of metabolic syndrome uniformly predict future
CV outcomes and type 2 diabetes in minority populations.
These inconsistent reports suggest that
race/ethnicityspecific cutoff points and criteria for metabolic syndrome
may be necessary to affirm the predictive values of the metabolic syndrome on
future CVD and type 2 diabetes in each ethnic and racial population.
Furthermore, and most importantly, prospective studies on the predictive values
of each of the components of the metabolic syndrome for CVD in various ethnic
and racial groups are urgently warranted. The time has come.
Kwame Osei, MD, is Ralph W. Kurtz Professor of
Medicine and Exercise Physiology and Director of the Division of Endocrinology,
Diabetes and Metabolism at Ohio State University Medical Center.