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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 30, No 1, January/February 2019
AFRICA
25
poverty appear to be a major concern in South African rural
areas, including Ellisras.
14
Details of the Ellisras Longitudinal Study (ELS) research
design and sampling procedure have been reported elsewhere.
15,16
For the purpose of this analysis, a total of 742 young adults aged
22 to 30 years (365 females and 377 males), who were part of the
ELS, participated in this survey.
The ethics committee of the University of the North, now
known as the University of Limpopo, granted approval prior to
the survey. Participants read and signed informed consent forms.
All subjects went through a series of anthropometric
measurements based on the standard procedures recommended
by the International Society for the Advancement of
Kinanthropometry (ISAK).
17
Skinfold (triceps, biceps,
subscapular and supraspinale) and height were measured using
both the Martin anthropometer and SlimGuide skinfold calliper.
Height was rounded off to the nearest 0.1 cm and skinfolds were
measured three times, where the values were rounded off to the
nearest 0.1 mm. A flexible steel tape was used to measure WC in
centimetres as participants assumed a standing position. WC was
measured sideways from midway between the lowest portion of
the rib cage and iliac crest and anteriorly, midway between the
xiphoid process of the sternum and the umbilicus.
Measurements for both systolic (SBP) and diastolic blood
pressure (DBP) were taken at least three times with the electronic
Micronta monitoring kit at an interval of five minutes, after
the participants had been sitting for at least 15 minutes in a
well-ventilated room.
18,19
The device contained an infrasonic
transducer that keeps records of BP and pulse rate on the
display screen. The device has been used for research and clinical
purposes.
20
Readings taken with a conventional mercury
sphygmomanometer and an automated device showed a high
correlation (
r
=
0.93), based on a pilot study conducted before
the actual survey.
Readings for intra- and inter-tester technical errors of
measurement (% TEM) for height, skinfolds and WC ranged
from 0.04 to 4.16 cm (0.2–5.01%), 0.2 to 6 mm (0.4–6.8%) and 0
to 3.4 cm (0–4%), respectively.
12
Statistical analysis
Descriptive statistics for WC, WHR and skinfold thickness
were computed. Independent
t
-tests were calculated to examine
whether there were any significant gender differences in the
participants’ anthropometric and haemodynamic measurements.
Hypertension was defined as SBP
≥
140 mmHg or DBP
≥
90
mmHg, according to WHO.
21
Central obesity was assessed based
on WC and WHR as follows: WC in men
≥
102 cm and in women
≥
88 cm, and WHR
≥
0.5 cm in both men and women.
22
The
sum of four skinfold measurements (triceps, biceps, subscapular
and supraspinale), categorised as above the 85th percentile, was
used to determine general obesity, where young adults were
characterised as normal or excessively fat.
23
The association between BP, WHR, WC and skinfolds,
adjusted for age and gender, was assessed using a linear
regression model. The risk of developing hypertension among
young Ellisras adults who were obese or overweight was assessed
with multinomial logistic regression analysis. Data were analysed
using the Statistical Package for the Social Sciences (SPSS)
(version 23), with the level of significance set at
p
<
0.05.
Results
Table 1 presents descriptive statistics for anthropometric
parameters, skinfolds and BP among young Ellisras adults aged
22 to 30 years. Women showed significantly (
p
<
0.05) higher
mean average WC (82.49
±
14.73 cm) than men (74.74
±
9.56 cm)
(
p
<
0.000). Men showed a significantly higher mean SBP (125.33
±
2.60 mmHg) than women (114.32
±
10.23 mmHg).
Presented in Table 2 are the summary data on the prevalence
of hypertension, overweight and central obesity among the
participants as evaluated using anthropometric parameters (WC,
WHR and skinfold thickness). There was a higher significant (
p
<
0.000) prevalence of central obesity in women (69.6%) than
in men (1.4%), while the prevalence of overweight was higher
in men (15.4%) than women (15.1%), although not significant.
High SBP was significantly (
p
<
0.05) more prevalent in men
(14.0%) than in women (1.9%).
Table 3 indicates the Pearson correlation coefficients
between anthropometric parameters, skinfold thickness and
BP measurements. There were significant (
p
<
0.05) correlations
Table 2. Prevalence of central obesity, overweight and hypertension
among young rural Ellisras adults
Variable
Men,
n
(%)
Women,
n
(%)
p
-value*
High WC
5 (1.4)
134 (35.4)
0.000
High WHR
110 (30.2)
263 (69.6)
0.000
Overweight
56 (15.4)
57 (15.1)
0.142
High SBP
51 (14.0)
7 (1.9)
0.013
High DBP
11 (3.0)
9 (2.4)
0.312
Hypertension
8 (2.2)
5 (1.3)
0.003
WC, waist circumference; WHR, waist-to-hip ratio; SBP, systolic blood pres-
sure; DBP, diastolic blood pressure.
Table 3. Pearson’s correlation coefficient between blood pressure and
anthropometric parameters (skinfold thickness,WC andWHR)
Variable
Triceps
Biceps
Subscapular Supraspinale WHR Waist
Women
SBP 0.022** 0.021** 0.053**
0.140
0.175 0.237
DBP 0.046** 0.007** 0.013**
0.093
0.136 0.684
Men
SBP 0.012** 0.015** 0.120
0.016
0.231 0.303
DBP 0.059
0.017** 0.054**
0.068
0.171 0.211
**Correlation is significant at the 0.05 level (two-tailed).
SBP, systolic blood pressure; DBP, diastolic blood pressure.
Table 1. Descriptive statistics for anthropometric parameters, skinfold
thickness and blood pressure among young Ellisras adults
Variable
Men (
n
=
364) Women (
n
=
375)
p
-value
Age, years
25.44
±
2.60
25.52
±
2.53
0.636
SBP, mmHg
125.33
±
12.95 114.32
±
10.23* 0.000
DBP, mmHg
71.67
±
10.11
69.43
±
9.12*
0.002
Biceps skinfold, cm
3.62
±
2.10
10.70
±
6.44*
0.000
Triceps skinfold, cm
6.46
±
4.30
12.41
±
7.20*
0.000
Subscapular skinfold, cm 8.71
±
3.28
12.59
±
6.80*
0.000
Supraspinale skinfold, cm 5.11
±
3.57
12.34
±
7.19*
0.000
Waist-to-height ratio
0.434
±
0.082
0.509
±
0.122* 0.000
Waist circumference, cm 74.74
±
9.56*
82.49
±
14.73* 0.000
Mean
±
SD; *
p
<
0.05.
SBP, systolic blood pressure; DBP, diastolic blood pressure.