General characteristics of study participants
Three hundred and six (306) children were recruited for the study which included 152 children from rural area and 154 from urban area. Among the 152 children in the rural area, there were 83 girls and 69 boys while among the 154 children in urban area there were 88 girls and 66 boys. Although data is presented for girls and boys, the statistical comparisons are between urban and rural. Age, height and weight were similar between urban and rural children. NC, MUAC, TC and CC were significantly (p < 0.05) higher in urban than rural children. The WC, BMI and AC were similar between urban and rural children. Rural children had significantly (p < 0.001) higher SBP and PWV than urban children while DBP, MAP and HR were significantly (p < 0.001) different between urban and rural children. Albumin, ACR, TBARS and ADMA were significantly (p < 0.001) higher in rural children than in urban children while, creatinine and 8-OHdG were significantly (p < 0.001) higher in urban children than in rural children (Table 1).
Table 1
General characteristics of participating children by sex and location
|
Rural (95% CI)
|
Urban (95% CI)
|
p-value
|
|
Girls
|
Boys
|
Girls
|
Boys
|
|
N
|
83
|
69
|
88
|
66
|
|
Age (years)
|
7.91(7.65–8.17)
|
7.88(7.56–8.19)
|
8.34(8.08–6.67)
|
8.11(7.72–8.49)
|
0.320
|
HT (cm)
|
124.81 (122.93–126.70)
|
126.87(124.41-129.32)
|
129.81(125.29-134.33)
|
127.86(125.01-130.11)
|
0.198
|
WT(kg)
|
25.44(24.40–26.40)
|
27.46(25.11–29.82)
|
28.61(26.60-30.61)
|
28.10(26.03–30.17)
|
0.137
|
BMI (m2/kg)
|
16.4(15.8–16.9)
|
16.8(15.8–17.9)
|
17.2(16.4–18.0)
|
17.1(16.0-18.2)
|
0.276
|
NC(cm)
|
24.9(24.5–25.3)
|
26.2(25.6–26.7)
|
26.0(25.4–26.5)
|
26.6 (25. 9-23.4)
|
< 0.001
|
MUAC (cm)
|
19.3(18.8–19.8)
|
19.4 (18.5–20.2)
|
20.5(19.7–21.3)
|
20.3(19.4–21.2)
|
< 0.01
|
WC (cm)
|
58.8(57.4–60.3)
|
59.6(56.9–61.2)
|
58.5(56.5–60.5)
|
57.9(55.3–60.5)
|
0.184
|
TC (cm)
|
34.2(33.2–35.3)
|
36.1(34.4–37.7)
|
39.6(38.1–41.1)
|
35.9(33.5–38.3)
|
< 0.001
|
CC (cm)
|
24.4 (23.7–25.1)
|
25.5(24.5–26.5)
|
26.9(25.9–27.8)
|
26.6(25.4–27.7)
|
0.01
|
AC (cm)
|
18.3 (17.9–18.7)
|
19.1(18.4–19.8)
|
18.6(17.9–19.3)
|
18.9(18.1–19.9)
|
0.514
|
SBP (mmHg)
|
108.8(106.1-111.6)
|
107.9(104.0-111.9)
|
108.4(104.9-111.8)
|
107.7(104.7–110.0)
|
< 0.001
|
DBP (mmHg)
|
71.1(69.1–73.1)
|
68.4(65.9–71.0)
|
69.3(66.9–71.7)
|
69.5(66.2–72.9)
|
<0.001
|
HR (bpm)
|
89.8(86.3–93.3)
|
89.4(86.3–92.5)
|
93.2(90.4–96.0)
|
87.6(84.4–90.8)
|
<0.001
|
MAP (mmHg)
|
83.7(81.6–85.7)
|
82.18(79.87–84.50)
|
82.33(79.82–84.85)
|
82.54(79.54–85.54)
|
<0.001
|
PWV (m/s)
|
5.6(5.4–5.8)
|
8.9(2.3–15.6)
|
5.5(5.2–5.8)
|
8.8(2.5–15.1)
|
<0.001
|
Creatinine (mmo/L)
|
7.17(6.16–8.11)
|
8.65(6.52–10.78)
|
10.79(9.03–12.57)
|
8.46(6.53–10.37)
|
< 0.001
|
ADMA (ng/ml)
|
72.08(68.8-75.42)
|
76.41(73.80–79.60)
|
75.12(72.56–77.68)
|
73.18(66.32–80.04)
|
< 0.001
|
Albumin (mg/L)
|
47.06(-7.48-101.71)
|
38.66(-9.75-87.07)
|
41.78(-9.09-92.65)
|
5.02(2.65–7.38)
|
< 0.001
|
ACR (mg/mmol)
|
6.16(-0.01-12.33)
|
3.40(-0.90-7.71)
|
4.17(-1.51-9.85)
|
0.58(0.38–0.77)
|
< 0.001
|
TBARS (µM)
|
0.08(0.07–0.08)
|
0.09(0.05–0.12)
|
0.08(0.06–0.09)
|
0.07(0.05–0.08)
|
< 0.001
|
8-OHdG (ng/ml)
|
61.64(57.40-65.88)
|
66.66(58.34–74.97)
|
64.92(60.24–69.59)
|
65.53(59.55–71.51)
|
< 0.001
|
Results are expressed as mean (min CI –max CI); CI: Confidence interval; N: Number of children; HT: Height; WT: Weight; BMI: Body Mass Index; NC: Neck circumference; MUAC: Mid upper arm circumference; WC: Waist circumference; TC: Thigh circumference; CC: Calf circumference; AC: Ankle circumference; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; HR: Heart rate; MAP: Mean arterial pressure; PWV: Pulse wave velocity; ADMA: Asymmetric dimethylarginine; ACR: Albumin to creatinine ratio; TBARS: Thiorbarbituric acid reactive substances; 8-OHdG: 8-hydroxyl-deoxy-guanosine.
Prevalence Of Overweight/obesity And Pre-hypertension/hypertension Among Participating Children
Children were separated by location and sex to determine the prevalence of overweight/obesity and pre-hypertension/hypertension as shown in Table 2. The prevalence of overweight /obesity was 19.3% and was higher in children from urban settings (10.8%) compared to those from rural settings (8.5%). Overweight/obesity was more prevalent in girls than in boys. The prevalence of pre-hypertension/hypertension was 42.2% and was high in rural children (23.2%) than in urban children (19.0%). The prevalence of pre-hypertension/hypertension in rural girls (14.7%) almost doubled that of rural boys (8.5%) while the prevalence of pre-hypertension/hypertension in urban settings was the same (9.5%) in both girls and boys.
Table 2
Prevalence of overweight/obesity and pre-hypertension/hypertension
|
Cohort (%)
|
Rural (%)
|
Urban (%)
|
|
Rural
|
Urban
|
Girls
|
Boys
|
Girls
|
Boys
|
Overweight/Obesity
|
26(8.5)
|
33(10.8)
|
17(5.55)
|
9(2.9)
|
20(6.5)
|
13(4.2)
|
EBP/HBP
|
71(23.2)
|
58(19.0)
|
45(14.7)
|
26(8.5)
|
29(9.5)
|
29(9.5)
|
EBP: Elevated blood pressure; HBP: High blood pressure; %: Percentage indicates prevalence |
Effect of pulse wave velocity on cardiovascular risk factors
Children were classified by four inter-quartile ranges of their PWV in order to determine the effect of PWV on cardiovascular risk factors. SBP, MAP and DBP increased with increasing PWV and the differences were significant (p < 0.05) for MAP and DBP. However, HR did not show any specific pattern with the increasing quartiles of PWV. Similarly, BMI, ADMA, 8-OHdG, TBARS, creatinine, albumin and ACR were not significantly (p > 0.05) different among the PWV quartiles (Table 3).
Table 3
Effect of pulse wave velocity on cardiovascular risk factors
PWV
quartiles
|
1st quartile
|
2nd quartile (95% CI)
|
3rd quartile (95% CI)
|
4th quartile (95% CI)
|
p-value
|
N
|
3
|
77
|
79
|
134
|
|
BMI (m2/Kg)
|
22.1
|
17.1 (16.4–17.3)
|
16.2 (15.7–16.8)
|
16.8 (16.2–17.3)
|
0.60
|
SBP (mmHg)
|
105.2
|
106.9 (104.4-109.4)
|
108.3 (105.3-111.3)
|
109.4 (106.4-112.4)
|
0.51
|
DBP (mmHg)
|
68.26
|
68.5 (66.4–70.6)
|
71.0 (68.8–73.2)
|
71.1 (69.8–72.5)
|
< 0.001
|
HR (bpm)
|
90.49
|
89.7 (85.5–92.9)
|
90.4 (86.6–94.1)
|
89.9 (85.6–94.1)
|
0.89
|
MAP (mmHg
|
74.4
|
82.5 (80.1–85.0)
|
81.3 (79.4–83.3)
|
84.3 (82.5–86.0)
|
0.06
|
ADMA (ng/ml)
|
62.3
|
64.6 (60.3–68.9)
|
72.7 (69.6–76.8)
|
70.7 (66.8–74.5)
|
0.23
|
8-OHdG (ng/ml)
|
68.65
|
62.9 (58.2–67.7)
|
75.1 (51.2–99.0)
|
68.71 (59.1–78.5)
|
0.844
|
TBARS (µM)
|
0.02
|
0.07(0.06–0.09)
|
0.07 (0.06–0.08)
|
0.07 (0.06–0.09)
|
0.461
|
Creatinine (mmol/L)
|
7.05
|
7.9 (6.7–9.2)
|
8.2 (6.9–9.5)
|
7.9 (6.9–9.1)
|
0.915
|
Albumin (mg/L)
|
1.5
|
29.3 (-7.1-65.7)
|
31.3 (1.2–61.4)
|
29.2 (-2.8-61.2)
|
0.32
|
ACR (mg/mmol)
|
0.3
|
3.4 (-0.7-7.5)
|
4.7 (-0.5-9.9)
|
2.9 (0.3–5.5)
|
0.318
|
Results are expressed as mean (min CI – max CI); CI: Confidence interval; N: Number of children; BMI: Body mass index; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; HR: Heart rate; MAP: Mean arterial pressure; PWV: Pulse wave velocity; ADMA: Asymmetric dimethyl arginine; ACR: Albumin to creatinine ratio; TBARS: Thiorbarbituric acid reactive substances; 8-OHdG: 8-hydroxyl-deoxy-guanosine. PWV quartiles (m/s): 1st quartile:<3.38; 2nd quartile: 4.1and 5.20; 3rd quartile: 5.3 and 5.7; 4th quartile:>6.10.
Effect Of Asymmetric Dimethylarginine On Cardiovascular Risk Factors
There are currently no cut off values for ADMA in children. In order to study the effect of ADMA on cardiovascular risk factors, children were classified into inter-quartile ranges of ADMA quartiles. Creatinine, albumin, ACR and 8-OHdG significantly (p < 0.001) increased with increasing quartiles of ADMA. Though there was a trend of SBP, DBP, and HR to increase with increasing quartiles of ADMA, the differences were insignificant (p>0.05). Moreover, BMI, MAP and TBARS insignificantly (p > 0.05) did not show any specific pattern of distribution (Table 4).
Table 4
Effect of asymmetric dimethylarginine on risk factors of cardiovascular diseases
ADMA
quartiles
|
1st quartile (95%CI)
|
2nd quartile (95%CI)
|
3rd quartile (95%CI)
|
4th quartile (95%CI)
|
p-value
|
N
|
47
|
48
|
47
|
48
|
|
BMI (m2/Kg)
|
17.5(16.2–18.8)
|
16.4(15.9–16.9)
|
17.1(15.9–18.3)
|
16.6(16.1–17.2)
|
0.503
|
SBP (mmHg)
|
100.5(100.3-100.8)
|
107.9(104.8–111.0)
|
108.0(104.7-111.2)
|
108.3(105.2-111.4)
|
0.98
|
DBP (mmHg)
|
68.1(65.9–70.2)
|
68.7(66.4–70.9)
|
69.8(67.5–72.1)
|
70.2(68.5–71.9)
|
0.27
|
HR (bpm)
|
89.8(85.3–94.4)
|
90.5(86.2–94.9)
|
90.8(86.0-95.5)
|
91.3(87.5–93.6)
|
0.97
|
MAP (mmHg
|
85.9(82.8–88.9)
|
82.8(79.7–85.9)
|
82.2(70.2–84.8)
|
82.0(80.2–83.9)
|
0.664
|
8-OHdG (ng/ml)
|
64.6(36.4–92.9)
|
65.2(55.3–75.0)
|
66.7(63.3–70.1)
|
77.9(65.6–90.1)
|
< 0.001
|
TBARS (µM)
|
0.07(0.06–0.08)
|
0.08(0.06–0.11)
|
0.07(0.06–0.07)
|
0.07(0.06–0.08)
|
0.820
|
Creatinine (mmol/L)
|
5.6(4.3–6.9)
|
9.1(7.1–11.1)
|
9.7(8.2–11.1)
|
7.3(6.5–8.2)
|
<0.001
|
Albumin (mg/L)
|
6.0(2.7–5.3)
|
22.0(8.9–35.1)
|
36.9(-7.1-80.9)
|
35.4(-0.7-71.5)
|
0.016
|
ACR(mg/mmol)
|
1.2(0.5–1.9)
|
2.1(1.3–2.9)
|
3.8(-1.2-8.7)
|
4.6(0.6–8.6)
|
0.022
|
Results are expressed as mean (min CI –max CI); CI: Confidence interval; N: Number of children; BMI: Body mass index; SBP: Systolic blood pressure; DBP = Diastolic blood pressure; HR: Heart rate; MAP: Mean arterial pressure; ADMA: Asymmetric dimethylarginine; ACR: Albumin to creatinine ratio; TBARS: Thiorbarbituric acid reactive substances; 8-OHdG: 8-hydroxyl-deoxy-guanosine. ADMA quartiles (ng/ml): 1st quartile: <68.00; 2nd quartile: 68.4 and 75.1; 3rd quartile: 75.2 and 79.58; 4th quartile: >79.06. |
Relationship Between Endothelial Function Markers And Cardiovascular Risk Factors
Study participants were separated by sex and location to assess their relationship between endothelial function markers and cardiovascular risk factors. MAP positively correlated (p < 0.05) with ADMA and PWV in urban and rural girls. A positive relationship (p < 0.05) was observed between DBP and PWV in urban girls while rural girls showed a positive relationship (p < 0.05) between HR and ADMA. BMI positively correlated (p < 0.001) with PWV in rural and urban males. Creatinine positively correlated (p < 0.05) with ADMA in urban children and in rural girls. 8-OHdG positively correlated (p < 0.05) with ADMA in both urban and rural children while ACR showed a negative relationship with ADMA for rural boys and urban girls (Table 5).
Table 5
Correlation between endothelial function markers and cardiovascular risk factors
Correlation coefficient
|
ADMA
|
|
PWV
|
|
Location
|
Rural
|
Urban
|
|
Rural
|
Urban
|
|
Sex
|
Girls
|
Boys
|
Girls
|
Boys
|
Girls
|
Boys
|
Girls
|
Boys
|
BMI
|
-0.09
|
-0.01
|
-0.05
|
-0.05
|
0.10
|
0.2∗∗∗
|
0.01
|
0.767∗∗∗
|
DBP (mmHg)
|
0.1
|
0.1
|
0.2
|
0.2
|
0.1
|
0.1
|
0.4*
|
0.2
|
SBP (mmHg)
|
0.1
|
-0.2
|
0.1
|
0.2
|
0.1
|
-0.02
|
0. 0
|
-0.04
|
HR (bpm)
|
0.3*
|
0.02
|
0.1
|
-0.3
|
-0.1
|
-0.2
|
0.1
|
0.1
|
MAP
|
0.09
|
0.05
|
0.33*
|
-0.24
|
0.26*
|
0.01
|
0.18
|
0.08
|
Creatinine (mmol/L)
|
0.5*
|
0.1
|
0.4*
|
0.4*
|
-0.2
|
0.1
|
0.1
|
0.01
|
Albumin (mg/L)
|
0.1
|
-0.23
|
0.01
|
0.3
|
-0.1
|
0.2
|
0.1
|
-0.02
|
ACR (mg/mmol)
|
0.03
|
-0.4*
|
-0.3*
|
0.1
|
-0.03
|
0.2
|
-0.01
|
0.2
|
8-OHdG (ng/ml)
|
0.5*
|
0.5*
|
0.4*
|
0.7*
|
0.1
|
-0.2
|
0.08
|
0.01
|
TBARS (µM)
|
0.1
|
0.04
|
-0.1
|
-0.1
|
-0.2
|
0.1
|
-0.1
|
0.3
|
BMI: Body mass index; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; HR: Heart rate; MAP: Mean arterial pressure; BMI: Body mass index; PWV: Pulse wave velocity; ADMA: Asymmetric dimethylarginine; ACR: Albumin to creatinine ratio; TBARS: Thiorbarbituric acid reactive substance; 8-OHdG: 8-hydroxyl-deoxy-guanosine. ∗indicates significant relationship (p < 0.05).
Predictors Of Endothelial Dysfunctions
Age adjusted linear regression of a fitted model (Ffemales=2.204; Fmales=3.15; p = 0.05) for the relationship of ADMA with cardiovascular risk factors showed increased 8-OHdG to predict increased ADMA in rural females (R2 = 0.4, Adj.R2 = 0.219; p < 0.01) and rural males (R2 = 0.623, Adj.R2 = 0.425; p < 0.001). In urban females, an unfitted model (F = 2.128; p = 0.101) showed increased 8-OHdG to predict increased ADMA (R2 = 0.621, Adj.R2 = 0.329; p < 0.05) while in urban males a fitted model (F = 3.119; p = 0.036) showed creatinine, albumin, ACR and 8-OHdG to predict increased ADMA (R2 = 0.757, Adj.R2 = 0.514; p < 0.05). Age adjusted linear regression of an unfitted model in rural females (F = 1.201; p = 0.316) for the relationship of PWV with cardiovascular risk factors showed increased creatinine to predict increased PWV (R2 = 0.207, Adj.R2 = 0.035; p = 0.018) while a fitted model in rural males (F = 2.603 p = 0.026) showed increased BMI to predict increased PWV (R2 = 0.555, Adj.R2 = 0.341; p < 0.001). Also, a fitted model for urban boys (F = 4.326; p = 0.005) showed increased BMI to predict increased PWV (R2 = 0.76, Adj.R2 = 0.585; p < 0.001).
Table 5
Regression analysis on the relationship between cardiovascular risk factors and endothelial function markers
Regression coefficient
|
ADMA
|
|
PWV
|
|
Location
|
Rural
|
Urban
|
Rural
|
Urban
|
Sex
|
Girls
|
Boys
|
Girls
|
Boys
|
Girls
|
Boys
|
Girls
|
Boys
|
BMI
|
0.02
|
0.134
|
-0.66∗
|
-0.02
|
-0.17
|
0.75∗∗∗
|
0.38
|
0.99∗∗∗
|
DBP (mmHg)
|
-0.04
|
0.05
|
0.15
|
.037
|
0.03
|
0.34
|
0.25
|
0.30
|
SBP (mmHg)
|
-0.01
|
-0.30
|
0.29
|
-0.27
|
-0.05
|
-0.09
|
-0.27
|
-0.29
|
HR (bpm)
|
0.24
|
-0.05
|
-0.04
|
0.04
|
0.05
|
-0.28
|
0.27
|
0.14
|
MAP
|
-0.19
|
.022
|
-0.25
|
-0.06
|
0.22
|
0.22
|
-0.22
|
-0.04
|
Creatinine (mmol/L)
|
0.13
|
-0.09
|
0.78
|
1.00∗
|
-0.37∗
|
-0.17
|
0.01
|
-0.32
|
Albumin (mg/L)
|
-0.23
|
1.41
|
-0.53
|
-1.13∗
|
0.32
|
0.38
|
-1.71
|
-0.12
|
ACR (mg/mmol)
|
0.42
|
-1.54
|
0.71
|
1.00∗
|
-0.26
|
-0.42
|
1.62
|
0.19
|
8-OHdG (ng/ml)
|
0.49∗∗
|
0.74∗∗∗
|
0.69∗
|
0.67∗
|
0.16
|
-0.09
|
-0.21
|
0.17
|
TBARS (µM)
|
-0.20
|
0.01
|
-0.74
|
0.16
|
-0.13
|
0.29
|
0.32
|
-0.22
|
BMI: Body mass index; SBP: Systolic blood pressure; DBP: Diastolic blood pressure; HR: Heart rate; MAP: Mean arterial pressure; BMI: Body mass index; PWV: Pulse wave velocity; ADMA: Asymmetric dimethylarginine; ACR: Albumin to creatinine ratio; TBARS: Thiorbarbituric acid reactive substance; 8-OHdG: 8-hydroxyl-deoxy-guanosine; ∗indicates p < 0.05; ∗∗indicates p < 0.01; ∗∗∗indicates p < 0.001