CARDIOVASCULAR JOURNAL OF AFRICA • Vol 22, No 4, July/August 2011
208
AFRICA
Short Communication
The sensitivity of waist-to-height ratio in identifying
children with high blood pressure
BS MOTSWAGOLE, HS KRUGER, M FABER, JM VAN ROOYEN, JH DE RIDDER
Abstract
We determined the sensitivity of waist-to-height ratio
(WHtR) as a marker for high blood pressure in children aged
nine to 15 years (
n
=
1 131), from schools in the North West
province, South Africa. Anthropometric and blood pressure
measurements were taken. The sensitivity and specificity of
theWHtR to identify children with high blood pressure were
evaluated. At a cut-off value of 0.5, 7.9% of the girls and
3.4% of the boys had central adiposity. Thirteen per cent of
the children were hypertensive. The optimal WHtR cut-off
value to identify children with hypertension was 0.41 in both
boys and girls. Positive correlations were observed between
anthropometric indices. Using linear regression analyses,
age and body mass index were significant predictors of high
blood pressure in boys, while for girls it was height and
weight. Results suggest that adopting a WHtR cut-off value
<
0.5 could enhance the use of WHtR as a marker for high
blood pressure in children.
Keywords:
waist-to-height ratio, blood pressure, children, South
Africa
Submitted 12/5/10, accepted 12/8/10
Cardiovasc J Afr
2011;
22
: 208–211
DOI: 10.5830/CVJA–2010–062
Studies in both adults
1,2
and children
3-5
have suggested that
waist-to-height ratio (WHtR) is more strongly associated with
cardiovascular (CV) risk factors than body mass index (BMI).
Several clinically relevant properties of the waist-to-height ratio
have been pointed out, including its sensitivity as an early warn-
ing of health risk and its simplicity for calculation. Also, it has
been suggested that the same cut-off value may be used for both
genders.
6
Hence, it has been proposed as an alternative measure
for assessing central fatness in children on the basis that it is
relatively age independent and that in normalising for growth,
it might preclude the need for age-related reference charts.
3,4,7
This index, however, is yet to be validated within the paediatric
population.
8
Previously, Ashwell and colleagues (1996)
9
proposed an age-
independent universal cut-off value of 0.5 for predicting CV
risk. However, this value is yet to be tested to predict CV risk in
children (Sung
et al
. 2008).
10
This study was aimed at assessing
the diagnostic accuracy of WHtR as a marker for future cardio-
vascular events, such as high blood pressure in South African
children, and whether WHtR could be used as a marker for high
blood pressure.
Methods
The study population consisted of 919 black South African
children aged nine to 15 years, drawn from the THUSA BANA
(Transition and Health during Urbanisation of South Africans;
BANA, children) study, conducted between May 2000 and June
2001. All anthropometric measurements were taken according
to standard methods
11
by qualified anthropometrists using cali-
brated apparatus.
Weight was measured to the nearest 0.1 kg on a calibrated
electronic scale (Precision Health Scale) and height was meas-
ured to the nearest 0.1 cm with a stadiometer calibrated using a
steel measuring tape. Waist circumference (WC) was measured
to the nearest 0.1 cm, half way between the superior ridge of
the ilium and the lower border of the lowest floating rib, with a
flexible Lufkin anthropometric steel tape.
12
BMI was calculated
by weight divided by height (m)
2
and waist-to-height ratio was
derived by dividing waist circumference (cm) by height (cm).
The triceps and subscapular skinfolds were measured on the
right side following standard techniques
13
(Lohman, 1988), and
were used to calculate percentage body fat using Boileau
et al.
(1985)
14
formulae below:
Six to 11 years: (constant:
boys
=
3.4, girls
=
1.4)
% body fat
=
1.35 (sum of triceps
+
subscapular skinfold) –
0.012 (sum of triceps
+
subscapular skinfold)
2
– constant
12 to 14 years: (constant: boys
=
4.4, girls 12–13 years
=
2.4)
% body fat
=
1.35 (sum of triceps
+
subscapular skinfold) –
0.012 (sum of triceps
+
subscapular skinfold)
2
– constant
15 to 18 years: (constant: boys
=
5.4, girls 14–15 years
=
3.4)
% body fat
=
1.35 (sum of triceps
+
subscapular skinfold) –
0.012 (sum of triceps + subscapular skinfold)
2
– constant
Centre of Excellence for Nutrition, North-West University,
Potchefstroom, South Africa
BS MOTSWAGOLE, MSc,
HS KRUGER, PhD,
Nutritional Intervention Research Unit, Medical Research
Council, Tygerberg, South Africa
M FABER, PhD
Faculty of Health Sciences, North-West University,
Hypertension in Africa Research Team (HART),
Potchefstroom, South Africa
JM VAN ROOYEN, DSc
JH DE RIDDER, PhD
