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VOLUME 12 NUMBER 1 • JULY 2015
39
SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
of the metabolic syndrome were elevated blood pressure, low
HDL-C levels and high WC, suggesting a high risk for CV diseases
in this occupational cohort. Therefore, considering the on-going
socio-economic changes in Angola, the findings of this study may
reflect the impact of the nutritional transition, behavioural and
occupational changes, environmental risk factors and unhealthy
lifestyle (mainly sedentary) with rapid weight gain, and the high
consumption of salty and high caloric food.
Although this study showed a good concordance between the
two criteria, the crude prevalence estimated with the JIS definition
was 10.2% higher than that estimated with ATP III. This difference
was mainly attributed to the different cut-off point for WC, which
is lower for JIS than for ATP III criteria.
It is known that WC reflects both visceral and subcutaneous
fat depots, but it has been used as a crude but relevant index of
visceral adiposity. The role of visceral adiposity in the development
of each metabolic syndrome component has been shown in non-
African populations.
36-39
In sub-Saharan African populations, a high
WC was suggested as a key determinant for development of the
metabolic syndrome.
14
However, since country-specific cut-off values of WC still need
to be defined for Africans, the cut-off values of WC derived
from European population groups have been recommended for
Africans.
5,7
Emerging data suggested that African-specific cut-off
values would be different from European cut-off values currently
recommended by the IDF.
18,24,25
In this study, the cut-off values for
men were lower than that currently recommended for Africans
(87.5 instead of 94 cm);
5,7
whereas for women, these cut-off values
were similar to those recommended for European and African
women (80.5 vs 80 cm).
A few studies have attempted to establish cut-off values of WC
for African groups,
18,24,25
and they found different cut-off values from
those currently recommended. In our study, the value of 87.5 cm for
men is similar to that reported in South African studies of African
men (86 cm),
18
but different for women.
18,25
However, our findings
differed from those reported for men and women in another study
of the same population (men: 90 cm, women: 98 cm).
24
Discordant cut-off values of WC between different studies are
to be expected since even in the same ethnic group, the WC may
vary according to the country, as emphasised by the IDF
5
and the
JIS.
7
Furthermore, it has been reported that variation in WC cut-off
values obtained using the sensitivity and specificity approach were
strongly correlated with mean levels of WC in the population.
40,41
The
cut-off values increased linearly with increasing population means,
independent of WC measurement techniques and regardless of
whether the health outcome was hypertension, dyslipidaemia,
hyperglycaemia or a cluster of multiple outcomes.
40
However, it
remains to be clarified whether this variation was due to biological
characteristics or the methodological approaches used to define
the best cut-off point.
40
In this study, women had higher mean values of WC than
men (Table 1). It is known that the proportion of total fat in
subcutaneous depots is higher in women than men.
42
Therefore
there is a potential risk of misclassification of women as having
excessive visceral adiposity by using values of WC to predict other
components of the metabolic syndrome. To minimise this difficulty
in this study and ensure a correct classification for only women
with strong evidence of two or more components of the metabolic
syndrome, we selected the best cut-off values of WC, as suggested
by the higher values of the Youden index. Therefore, this study
reinforces the opinion that definition of cut-off values of WC should
be country- and gender-specific.
There was a potential limitation to this study. Because we studied
a convenient sample consisting of staff of a public university, our
findings may not apply to the Angolan population as a whole. As
previously detailed,
27
however, participants were recruited from all
higher education institutions, which represented university staff in
the whole country. When this study was designed in 2009, all
university staff were invited to take part. The study group included
all occupational and socio-economic classes, including teachers and
non-teaching workers.
26,27
Conclusion
There was a high prevalence of the metabolic syndrome in this
occupational cohort, with a higher prevalence among women. This
study suggested that optimal cut-off values of WC of 87.5 cm and
80.5 cm would be appropriate for the diagnosis of the metabolic
syndrome in men and women, respectively. This may imply that
the prevalence would have been different from that reported in
this study if these values had been used. Further investigation is
therefore needed to confirm optimal cut-off values of WC in the
general Angolan population, in order to consistently estimate the
trends of cardiometabolic risk factors in African populations.
Acknowledgement
This study was supported by grants from Fundação para Ciência e Desenvolvimento,
Angola and CAPES, Brazil.
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