CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 9, October 2012
504
AFRICA
=
683.41
pg/min and interquartile range
=
500.26–1276.29
pg/
min). These data were used in the binary logistic regression
analysis (Table 2).
Table 2 describes the magnitude of the relationship
(
unadjusted and adjusted odds ratios) between the selected risk
factors (BMI
≥
85
th percentile; body fat %
≥
25%
for boys
and
≥
32%
for girls; VO
2
max
≤
50
th percentile) and elevated
(
defined as
≥
75
th percentile) salivary CRP concentration and
secretion rate, calculated as
≥
1372.14
pg/ml and
≥
1276.39
pg/min, respectively. Only a poor CRF (
≤
50
th percentile)
was independently associated with elevated salivary CRP
concentrations (
≥
75
th percentile,
≥
1372.14
pg/ml) (OR 3.9,
95%
CI: 1.7–8.9,
p
=
0.001).
However, both poor CRF (OR
2.7, 95%
CI: 1.2–6.1,
p
=
0.02)
and overweight/obesity (BMI
≥
85
th percentile) (OR 2.5, 95% CI: 1.1–5.9,
p
=
0.03)
were
independent predictors of elevated salivary CRP secretion rates
(
≥
75
th percentile,
≥
1276.39
pg/ml).
Discussion
The present study aimed to determine the relationship between
salivary CRP, a non-invasive alternative marker of systemic
inflammation, and body composition and/or CRF in black South
African children. The main findings of this study were that poor
CRF was an independent predictor of elevated salivary CRP
concentration, while poor CRF and being overweight/obese
were independent predictors of elevated salivary CRP secretion
rate. The study suggests that both CRF and body composition
are associated with elevated inflammatory status in black
South African children and provides initial evidence that the
measurement of salivary CRP may be a useful tool for examining
the health status of children.
The study found that a normal BMI does not induce a state
of inflammation as reflected by significantly lower salivary CRP
concentration and secretion rates in normal weight compared
to obese children. In addition, a normal weight was associated
with a higher aerobic capacity (VO
2
max
)
and lower SBP and DBP
compared to obesity.
The binary logistic regression analysis indicated themagnitude
of the relationship between the risk factors and inflammatory
status of the children. The results demonstrated that the odds
ratio for the association between poor CRF and elevated salivary
CRP concentration in children was 3.9. However, the odds ratio
for elevated salivary CRP secretion rate if the children had both
poor CRF and were overweight/obese was 6.8 (2.7
×
2.5).
These results are similar to previous research examining the
relationship between serum CRP, CRF and body composition
in Canadian children and young adults (6–24 years),
23
and black
South African children (13–18 years).
13
The results for salivary
CRP concentration is supported by a recent study demonstrating
an inverse relationship between serum CRP levels and CRF that
was independent of body composition and fat distribution.
7
In
addition, serum CRP concentrations in the overweight and obese
categories were significantly higher in the low CRF category.
7
The results from the present study therefore seem to support
the hypothesis that regular exercise or physical activity and/or
decreased visceral fat mass decreases low-grade inflammation.
1,6,11
The present results, together with the recent finding that
salivary CRP is a good measure of discrimination for the
clinically relevant serum CRP cut-off point in adults,
7,16
suggest that salivary CRP could be used as an alternative
marker of cardiovascular or chronic disease risk in children.
However, research is required to establish the relevance and cost
effectiveness of this inflammatory marker in clinical practice.
In future, the determination of a clinically relevant index
of salivary CRP may facilitate the prospective measurements
of CRP levels in large epidemiological samples and contribute
to understanding the mechanisms by which inflammation may
be associated with the development of chronic disease in
children. In addition, a clinically relevant index of salivary
CRP may also be integrated into a broader multi-systemic
TABLE 1. DEMOGRAPHIC, BODY COMPOSITION, CRF
DATA FOR NORMALWEIGHT, OVERWEIGHTAND OBESE
CHILDREN. VALUESARE MEAN
±
STANDARD DEVIATION
Normal
(
n
=
93)
(
males 38;
females 55)
Overweight
(
n
=
24)
(
males 8;
females 16)
Obese
(
n
=
53)
(
males 24;
females 29)
Age (years)
9.71 (1.84)
9.25 (1.67)* 9.55 (1.63)
Height (cm)
137.12 (12.10) 137.75 (11.59) 140.75 (9.73)#
Mass (kg)
32.24 (7.68)** 37.90 (9.09)** 52.49 (13.68)**
BMI (kg/m
2
)
16.88 (1.50)** 19.64 (1.49)** 26.17 (5.03)**
Waist–hip ratio
0.77 (0.04)
0.79 (0.05)
0.83 (0.06)
Body fat (%)
19.39 (5.03)** 27.81 (5.02)** 36.42 (7.10)**
Resting HR (bpm)
85.96 (13.64) 84.54 (10.80) 85.57(13.53)
SBP (mmHg)
94.62 (11.99) 94.08 (7.63) 105.65 (12.06)
#
DBP (mmHg)
62.25 (12.18) 62.67 (5.77)
72.55 (10.40)
#
VO
2
max
(
ml/kg/min)
28.61 (5.45)
25.02 (3.89)
22.72 (3.28)
#
Salivary CRP (pg/ml)
6.77 (0.92)
6.85 (0.85)
7.31 (0.93)
&
Salivary CRP (pg/min) 6.68 (0.98)
6.79 (0.75)
7.25 (0.99)
&
*
p
<
0.05
for overweight vs normal weight;
**
p
<
0.001
for all weight categories different from each other;
#
p
<
0.05
for obese vs normal weight and overweight;
&
p
<
0.05
for obese vs normal weight.
TABLE 2. UNADJUSTEDANDADJUSTED RISK FACTORS FOR ELEVATED SALIVARY CRP IN CHILDREN
Risk factor
%
of children with elevated
salivary CRP and risk
factor present (%)
%
of children with elevated
salivary CRP and risk
factor absent (%)
Unadjusted odds
ratio (95% CI)
Adjusted odds
ratio (95% CI)
p
-
value
Salivary CRP concentration
VO
2
max
≤
50
th percentile
35.3
12.3
3.9 (1.7–8.9)
3.9 (1.7–8.9)
0.001
BMI
≥
85
th percentile
30.6
17.8
2.0 (1.0–4.3)
1.0 (0.3–3.2)
0.944
Body fat (%)
≥
25%
for boys and
≥
32%
for girls
34.3
17.0
2.5 (1.2–5.3)
1.7 (0.7–3.7)
0.221
Salivary CRP secretion rate
VO
2
max
≤
50
th percentile
34.5
13.5
3.4 (1.2–7.5)
2.7 (1.2–6.1)
0.02
BMI
≥
85
th percentile
34.1
13.7
3.3 (1.5–7.3)
2.5 (1.1–5.9)
0.03
Body fat (%)
≥
25%
for boys and
≥
32%
for girls
37.1
14.8
3.4 (1.6–7.3)
1.8 (0.6–5.5)
0.40
