J Clin Med Res

Journal of Clinical Medicine Research, ISSN 1918-3003 print, 1918-3011 online, Open Access

Article copyright, the authors; Journal compilation copyright, J Clin Med Res and Elmer Press Inc

Journal website http://www.jocmr.org

Original Article

Volume 4, Number 3, June 2012, pages 197-205

Serum 25-hydroxyvitamin D and Ethnic Differences in Arterial Stiffness and Endothelial Function

Figure 1. Relationship of 25(OH)D with AIx75, supine SBP, and aortic blood pressures, adjusted for age, sex, and percent body fat. Filled circles indicate AA, open circles indicate EA.

Figure 2. Ethnic differences in vascular function a) unadjusted, b) adjusted for age and percent body fat, and c) further adjusted for 25(OH)D.

**Table 1.** Descriptive Characteristics Among all Participants and by Ethnic Group
Variables	All (n = 45)	AA (n = 23)	EA (n = 22)	P_{ethnic group}^a
Abbreviations: AA, African American; EA, European American; BMI, body mass index. ^aAs measured by two-group t-test. ^bn = 22, ^cn = 19, ^†n = 22
Age (yr)	29.1 ± 6.8	31.0 ± 6.3	27.1 ± 6.9	0.06
Female gender (%)	80%	87%	73%	0.23
Height (cm)	167.1 ± 7.5	167.4 ± 6.9	166.7 ± 8.3	0.76
Weight (kg)	68.9 ± 13.7	72.6 ± 13.8	65.0 ± 12.8	0.06
BMI (kg/m²)	24.5 ± 4.0	25.8 ± 4.2	23.2 ± 3.2	0.02
Waist circumference (cm)	77.0 ± 10.4	78.9 ± 10.8	74.9 ± 9.8	0.20
Percent body fat (%)	30.8 ± 8.0	33.7 ± 8.3	27.7 ± 6.5	0.01
SES total score	41.9 ± 13.5	39.2 ± 12.5^†	44.5 ± 14.2	0.20
Physical activity score	8.0 ± 1.4	7.9 ± 1.4^b	8.2 ± 1.4^c	0.57

Table 1. Descriptive Characteristics Among all Participants and by Ethnic Group

Variables

All (n = 45)

AA (n = 23)

EA (n = 22)

P_{ethnic group}^a

Abbreviations: AA, African American; EA, European American; BMI, body mass index. ^aAs measured by two-group t-test. ^bn = 22, ^cn = 19, ^†n = 22

Age (yr)

29.1 ± 6.8

31.0 ± 6.3

27.1 ± 6.9

0.06

Female gender (%)

80%

87%

73%

0.23

Height (cm)

167.1 ± 7.5

167.4 ± 6.9

166.7 ± 8.3

0.76

Weight (kg)

68.9 ± 13.7

72.6 ± 13.8

65.0 ± 12.8

0.06

BMI (kg/m²)

24.5 ± 4.0

25.8 ± 4.2

23.2 ± 3.2

0.02

Waist circumference (cm)

77.0 ± 10.4

78.9 ± 10.8

74.9 ± 9.8

0.20

Percent body fat (%)

30.8 ± 8.0

33.7 ± 8.3

27.7 ± 6.5

0.01

SES total score

41.9 ± 13.5

39.2 ± 12.5^†

44.5 ± 14.2

0.20

Physical activity score

8.0 ± 1.4

7.9 ± 1.4^b

8.2 ± 1.4^c

0.57

**Table 2.** Serum 25(OH)D and Vascular Measures Among all Participants and by Ethnic Group
Variables^a	All	AA	EA	P_{ethnic group}^b
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; AA, African American; EA, European American; SBP, systolic blood pressure; DBP, diastolic blood pressure; AIx, augmentation index; AIx75, augmentation index standardized to a heart rate of 75 beats/min; PWV, pulse wave velocity; FMD, flow-mediated dilation. ^an = 23 AA, 22 CA unless otherwise specified. ^bAs measured by two-group t-test. ^cTo convert to nmol/L, multiply by 2.946. ^dDefined as 25(OH)D ≤ 20 ng/mL. ^en = 22, ^fn = 21, ^gn = 18.
25(OH)D (ng/mL)^c	21.9 ± 10.1	15.2 ± 5.1	28.8 ± 9.4	< 0.001
Vitamin D insufficiency^d (n, %)	23 (51%)	18 (82%)	4 (18%)	< 0.001
Seated SBP (mmHg)	110 ± 13	109 ± 12	109 ± 14	0.96
Seated DBP (mmHg)	68 ± 8	70 ± 8	67 ± 7	0.26
Supine SBP (mmHg)	115 ± 11	116 ± 9^e	113 ± 12	0.36
Supine DBP (mmHg)	72 ± 7	72 ± 6^e	71 ± 9	0.48
Heart rate (beats/min)	64 ± 8	65 ± 8	62 ± 8	0.18
AIx (%)	10.9 ± 10.2	14.9 ± 9.1	6.6 ± 9.6^f	0.005
AIx75 (%)	5.6 ± 10.7	10.2 ± 8.1	0.5 ± 11.1^f	0.002
Aortic SBP (mmHg)	101 ± 9	103 ± 7	99 ± 10	0.08
Aortic DBP (mmHg)	72 ± 8	74 ± 6	71 ± 10	0.26
PWV (m/s)	6.6 ± 0.8	7.0 ± 0.8^e	6.2 ± 0.7^g	0.005
Baseline diameter (mm)	0.35 ± 0.05	0.35 ± 0.06^e	0.34 ± 0.05^f	0.60
FMD (%)	9.54 ± 2.44	8.61 ± 2.16^e	10.52 ± 2.39^f	0.009

Table 2. Serum 25(OH)D and Vascular Measures Among all Participants and by Ethnic Group

Variables^a

All

P_{ethnic group}^b

Abbreviations: 25(OH)D, 25-hydroxyvitamin D; AA, African American; EA, European American; SBP, systolic blood pressure; DBP, diastolic blood pressure; AIx, augmentation index; AIx75, augmentation index standardized to a heart rate of 75 beats/min; PWV, pulse wave velocity; FMD, flow-mediated dilation. ^an = 23 AA, 22 CA unless otherwise specified. ^bAs measured by two-group t-test. ^cTo convert to nmol/L, multiply by 2.946. ^dDefined as 25(OH)D ≤ 20 ng/mL. ^en = 22, ^fn = 21, ^gn = 18.

25(OH)D (ng/mL)^c

21.9 ± 10.1

15.2 ± 5.1

28.8 ± 9.4

< 0.001

Vitamin D insufficiency^d (n, %)

23 (51%)

18 (82%)

4 (18%)

< 0.001

Seated SBP (mmHg)

110 ± 13

109 ± 12

109 ± 14

0.96

Seated DBP (mmHg)

68 ± 8

70 ± 8

67 ± 7

0.26

Supine SBP (mmHg)

115 ± 11

116 ± 9^e

113 ± 12

0.36

Supine DBP (mmHg)

72 ± 7

72 ± 6^e

71 ± 9

0.48

Heart rate (beats/min)

64 ± 8

65 ± 8

62 ± 8

0.18

AIx (%)

10.9 ± 10.2

14.9 ± 9.1

6.6 ± 9.6^f

0.005

AIx75 (%)

5.6 ± 10.7

10.2 ± 8.1

0.5 ± 11.1^f

0.002

Aortic SBP (mmHg)

101 ± 9

103 ± 7

99 ± 10

0.08

Aortic DBP (mmHg)

72 ± 8

74 ± 6

71 ± 10

0.26

PWV (m/s)

6.6 ± 0.8

7.0 ± 0.8^e

6.2 ± 0.7^g

0.005

Baseline diameter (mm)

0.35 ± 0.05

0.35 ± 0.06^e

0.34 ± 0.05^f

0.60

FMD (%)

9.54 ± 2.44

8.61 ± 2.16^e

10.52 ± 2.39^f

0.009

**Table 3.** Pearson Correlations of 25(OH)D With Vascular Outcomes (r (P-value))
	25(OH)D
Abbreviations: 25(OH)D, 25-hydroxyvitamin D; AIx75, augmentation index standardized to a heart rate of 75 beats/min; PWV, pulse wave velocity; FMD, flow-mediated dilation; SBP, systolic blood pressure; DBP, diastolic blood pressure.
AIx75	- 0.35 (0.02)
PWV	- 0.39 (0.009)
FMD	0.37 (0.01)
Seated SBP	- 0.14 (0.37)
Seated DBP	- 0.11 (0.48)
Supine SBP	- 0.29 (0.06)
Supine DBP	- 0.11 (0.46)
Aortic SBP	- 0.32 (0.03)
Aortic DBP	- 0.27 (0.08)

Table 3. Pearson Correlations of 25(OH)D With Vascular Outcomes (r (P-value))

25(OH)D

Abbreviations: 25(OH)D, 25-hydroxyvitamin D; AIx75, augmentation index standardized to a heart rate of 75 beats/min; PWV, pulse wave velocity; FMD, flow-mediated dilation; SBP, systolic blood pressure; DBP, diastolic blood pressure.

AIx75

- 0.35 (0.02)

PWV

- 0.39 (0.009)

FMD

0.37 (0.01)

Seated SBP

- 0.14 (0.37)

Seated DBP

- 0.11 (0.48)

Supine SBP

- 0.29 (0.06)

Supine DBP

- 0.11 (0.46)

Aortic SBP

- 0.32 (0.03)

Aortic DBP

- 0.27 (0.08)