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VOLUME 12 NUMBER 1 • JULY 2015
37
SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
and compared using the chi-square test or Fisher’s exact test if
appropriate. Prevalence of the metabolic syndrome was age-
standardised by direct method using as reference the world
population distribution as projected by the WHO for 2000 to 2025.
32
Age-specific prevalence of the metabolic syndrome was estimated
per age decades (< 30, 30–39, 40–49, 50–59 and ≥ 60 years).
ROC curve analysis was performed to determine the appropriate
cut-off points of WC for identifying subjects with two or more
components of the metabolic syndrome (except for WC), as defined
by the JIS criteria. For the purpose of this analysis, we considered
the presence or absence of the metabolic syndrome as an outcome
variable and WC as a testing variable.
Optimal values of WC were obtained from the Youden index
[maximum (sensitivity + specificity – 1)].
33
Positive predictive values
(PPV) and negative predictive values (NPV) were also presented.
The kappa coefficient was used to assess the statistical agreement
between the ATP III and JIS criteria for identify individuals with the
metabolic syndrome. A
p-
value < 0.05 was considered statistically
significant.
Results
A complete data set was collected for 615 subjects (52.2%women).
Compared with women (Table 1), men had higher mean values for
height, WHR, creatinine and uric acid levels (all
p
< 0.001), and
PP (
p
= 0.007). Women had higher means values for HDL-C, WC,
HC, BMI (all
p
< 0.001), and heart rate (
p
= 0.003). Age, weight,
SBP, DBP, MBP, and glucose, total cholesterol, LDL-C, VLDL-C, and
triglyceride levels were similar in both sexes.
Table 2 shows distribution of risk factors, socio-economic
and educational characteristics of the study population. Current
smoking was higher in men (
p
= 0.035), whereas prevalence of
overweight, obesity and low HDL-C levels were higher in women
(all
p
< 0.001). However, prevalence of hypertension, diabetes,
hypercholesterolaemia, hypertriglyceridaemia and high LDL-C levels
were similar in both sexes (Table 2).
The overall crude prevalence of the metabolic syndrome was
17.6% [age-standardised: 8.7%, 95% confidence interval (CI):
6.8–11.3] for the ATP III criteria and 27.8% (age-standardised:
14.1.0%, 95% CI: 11.6–17.1) for the JIS criteria. As expected, the
crude prevalence was higher in women than in men, irrespective
of the criteria used (Table 3). In both sexes, the prevalence of the
metabolic syndrome increased with age, however, women showed
a higher prevalence in all age groups from 30 years and older
(Table 3). Regarding socio-economic class and educational level
Table 2.
Risk factors, educational level and socioeconomic class of the
study population
Characteristics
All
Men
Women
p
-value
Hypertension,
n
(%)
278 (45.2)
136 (46.3)
142 (44.2)
0.615
Current smokers,
n
(%)
39 (6.3)
25 (8.5)
14 (4.4)
0.035
Diabetes,
n
(%)
35 (5.7)
16 (5.4)
19 (5.9)
0.799
Overweight,
n
(%)
180 (29.3)
80 (27.2)
100 (31.2) < 0.001
Obesity,
n
(%)
120 (19.5)
27 (9.2)
93 (29.0)
< 0.001
High TC,
n
(%)
68 (11.1)
31 (10.5)
37 (11.5)
0.698
High TGL,
n
(%)
77 (12.5)
37 (12.6)
40 (12.5)
0.963
High LDL-C,
n
(%)
121 (19.7)
61 (20.7)
60 (18.7)
0.522
Low HDL-C,
n
(%)
308 (50.1)
108 (36.7)
200 (62.3) < 0.001
Education level
0.926
Low,
n
(%)
213 (34.6)
110 (37.4)
103 (32.1)
Medium,
n
(%)
150 (24.4)
69 (23.5)
81 (25.2)
High,
n
(%)
252 (41.0)
115 (39.1)
137 (42.7)
Socio-economic class
0.392
Low,
n
(%)
154 (25.0)
81 (27.6)
73 (22.7)
Middle,
n
(%)
156 (25.4)
77 (26.2)
79 (24.6)
Upper middle,
n
(%)
152 (24.7)
66 (22.4)
86 (26.8)
Upper,
n
(%)
153 (24.9)
70 (23.8)
83 (25.9)
Values are number of subjects (
n
) and percentages (%).
Table 3.
Crude and age-standardised prevalence of the metabolic
syndrome in men and women according to ATP III and JIS criteria
Age group (years)
n
ATP III
JIS
Men (
n
= 294)
< 30
40
2 (5.0)
3 (7.5)
30–39
52
2 (3.8)
4 (7.7)
40–49
89
8 (9.0)
15 (16.9)
50–59
90
10 (11.1)
23 (25.6)
≥ 60
23
3 (13.0)
5 (21.7)
Total crude
294
25 (8.5)
50 (17.0)
Age-standardised
–
4.8
9.0
Women (
n
= 321)
< 30
32
0 (0.0)
1 (3.1)
30–39
71
8 (11.3)
13 (18.3)
40–49
125
43 (34.4)
62 (49.6)
50–59
79
27 (34.2)
37 (46.8)
≥ 60
14
5 (35.7)
8 (57.1)
Total crude
321
83 (25.9)
121 (37.7)
Age-standardised (%)
–
12.6
19.2
Overall (
n
= 615)
Crude
615
108 (17.6)
171 (27.8)
Age-standardised (%)
–
8.7
14.1
Values are
n
(%). ATP III, National Cholesterol Education Program Third Adult
Treatment Panel; JIS, Joint Interim Statement.
Table 4.
Prevalence of the metabolic syndrome from JIS criteria in men
and women according to socio-economic class and educational level
Number (%)
p
-value
Men
Socio-economic class
0.083
Low
8 (9.9)
Middle
13 (16.9)
Upper middle
11 (16.7)
Upper
18 (25.7)
Education level
0.444
Low
15 (13.6)
Medium
12 (17.4)
High
23 (20.0)
Women
Socio-economic class
0.199
Low
29 (39.7)
Middle
28 (35.4)
Upper middle
26 (30.2)
Upper
38 (45.8)
Education level
0.294
Low
45 (43.7)
Medium
27 (33.3)
High
49 (35.8)
Values are number of subjects (
n
) and percentages (%).