CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 3, April 2013
96
AFRICA
historically one of the major determinants
of insulin resistance; whereas peripheral
subcutaneous adipose tissue (VAT)
has been shown to be ‘protective’ in
predominantly white populations.
However, numerous studies indicate that
at the same level of body mass index
(BMI) or waist circumference, black
women are more insulin resistant than
their white counterparts in spite of having
less VAT and hepatic steatosis.
In white women, VAT is the most
significant determinant of insulin
sensitivity, whereas in black women this
is more closely associated with abdominal
SAT. Gluteal SAT is negatively correlated
with insulin sensitivity in black but not
white women. The larger SAT adipocyte
size in black women is associated with
a reduced adipogenic capacity and a
higher expression of inflammatory genes
compared with their white counterparts.
Questions raised include whether
adipose tissue hypertrophy in black
women is associated with increased
hypoxia and/or oxidative stress in SAT
and consequently insulin resistance.
1.
Goedecke JH, Levitt NS, Evans J, Ellman
N, Hume DJ, Kotze L,
et al
. The role
of adipose tissue in insulin resistance in
women of African ancestry.
J Obesity
2013, Article ID 952916.
.
org/10.1155/2013/952916.
Population-specific cut-off
points proposed for diagnosis
of the metabolic syndrome in
South Africa
Nigel Crowther and Shane Norris of the
Witwatersrand University’s Departments
of Chemical Pathology and Paediatrics
question the appropriateness of the
European guidelines used for the
diagnosis of the metabolic syndrome in
sub-Saharan African women. Their study
measured the prevalence of obesity and
related metabolic disorders in an urban
population of black women to determine
the appropriate waist cut-off point for
diagnosing metabolic syndrome.
1
Of 1 251African females from the Birth
to Twenty cohort in Soweto, prevalence
of obesity, T2D and the metabolic
syndrome were 50.1, 14.3 and 42.1%,
respectively. The appropriate waist cut-off
point was found to be 91.5 cm (currently
recommended levels are 80.0 cm) and
was similar to the cut-off points obtained
for detecting increased risk of insulin
resistance (89.0 cm), dyscglycaemia (88.4
cm), hypertension (90.1 cm), hypo-high-
density lipoproteinaemia (87.6 cm) and
hyper-low-density lipoproteinaemia (90.5
cm). The similar waist cut-off points
identified for the detection of the individual
components of the metabolic syndrome
and related cardiovascular risk factors
demonstrates that the risk for different
metabolic diseases increases at the same
level of abdominal adiposity, suggesting a
common aetiological pathway.
Salome Kruger and colleagues from the
Centre of Excellence for Nutrition at the
North West University’s Potchefstroom
campus propose a cut-off point of waist-to-
height ratio (WHtR) of 0.41 for metabolic
risk in African township adolescents.
2
It has previously been proposed that a
WHtR
>
0.5 be the cut-off point for
abdominal obesity in both genders and
all ages. To date it is unknown if this
cut-off point is appropriate for previously
undernourished adolescents.
Assessment of the cut-off value
of WHtR associated with increased
metabolic risk was performed in 178
black South African adolescents aged
between 14 and 18 years. The WHtR
cut-off points ranged from 0.40 to 0.41,
with best diagnostic value at 0.41.
A WHtR of 0.40 had 80% sensitivity
and 38.5% specificity to classify fasting
blood glucose
>
5.6 mmol/l. A WHtR
of 0.41 had 64% sensitivity and 58.5%
specificity for a HOMA-IR
>
3.4; 55%
sensitivity and 55.6% specificity for a
high-sensitivity C-reactive protein level
>
1 mg/l; and a 64% sensitivity and 50.2%
specificity for a blood pressure higher
than the age-, gender-, and height-specific
90th percentiles.
1.
Crowther NJ and Norris SA. The current
waist circumference cut point used for the
diagnosis of metabolic syndrome in sub-
Saharan African women is not appropriate.
PLOS ONE
2012;
7
(11): e48883.
2.
Kruger HS, Faber M, Schutte AE, Ellis SM.
A proposed cutoff point of waist-to-height
ratio for metabolic risk in African township
adolescents.
Nutrition
2013;
29
(3): 502–507.
Geographic variation of
hypertension in South Africa
A study arising out of the Division of
Health Sciences, University of Warwick
Medical School, Coventry, UK, examines
the geographic variation of hypertension
in South Africa.
1
Analysis of the South
African Demographic and Health Survey
of 13 596 individuals older than 15 years
mapped the geographic distribution of
hypertension at the provincial level,
accounting for individual risk factors.
Overall prevalence of hypertension
(blood pressure
≥
140/90 mmHg or self-
reported diagnosis or on medication) was
30.4%. Higher prevalence of hypertension
was significantly associated with current
smoking, current drinking, self-reported
sleep problems and the presence of
cardiovascular comorbidities such as T2D.
The North West, Free State and
Northern Cape provinces had the highest
prevalence of hypertension, with the
lowest levels found in Limpopo. These
geographic variations suggest the potential
role of socio-economic, nutritional and
environmental factors beyond individual-
level risk factors in the development of
hypertension.
1.
Kandal NB, Tigbe W, Manda SO, Stranges S.
Geographic variation of hypertension in sub-
Saharan Africa: a case study of South Africa.
Am J Hypertens
2012;
26
(3): 382–391.
NCD risk factors in a high-
HIV-prevalence rural setting
Abraham Malaza of the Africa Centre for
Health and Population Studies, University
of KwaZulu-Natal, and colleagues
examined adult hypertension and obesity
in a high-HIV-prevalence rural area.
1
The prevalence of obesity in women was
6.5 times higher than in men, whereas
prevalence of hypertension was 1.4 times
higher than in men.
Obesity was a bigger risk factor for
hypertension in men and overweight was
a risk factor for men only. The BMI
of men and women on antiretroviral
treatment (ART) was lower than that of
their HIV-negative counterparts.
The negative association of ART
with BMI could be attributed to late
presentation and initiation of individuals
on ART and the associated weight loss
with advanced HIV disease progression. It
is also possible that HIV-infected persons
are more in contact with healthcare
services, so they may be more susceptible
to adopting nutrition-related advice.
1.
Malaza A, Mossong J, Barnighausen T,
Newell ML. Hypertension and Obesity in
Adults Living in a High HIV Prevalence
Rural Area in South Africa.
PLOS ONE
2012;
7
(10): e47761.
G Hardy
