Symmetrical Ambulatory Arterial Stiffness Index: Relationship with Serum Cystatin C Levels

Figures & data

Table 1. Baseline demographic, clinical, procedural, and laboratory findings of population divided according to the cystatin C quartiles

Quartile	1	2	3	4
n	22	22	21	22
Age, years	48.5 ± 13.5*	57.7 ± 12.0*	60.8 ± 11.3**	70.2 ± 7.3
Gender (men/women)	10/12	6/16	9/12	9/13
Diabetics	6	5	9	9
Waist perimeter, cm	96.2 ± 12.6***	101.7 ± 13.0	100.5 ± 17.3	104.5 ± 12.8
Body mass index, kg/m^2	29.8 ± 4.4	30.5 ± 5.4	30.2 ± 7.0	32.9 ± 5.9
Mean serum creatinine, mg/dL	0.75 ± 0.15*	0.80 ± 0.15*	0.90 ± 0.20**	1.21 ± 0.42
Mean cystatin C, mg/L	0.60 ± 0.07*	0.74 ± 0.05*	0.91 ± 0.05*	1.35 ± 0.33
Mean eGFR, mL/min (MDRD)	108.0 ± 21.4*	101.4 ± 19.1*	86.1 ± 27.7**	61.4 ± 18.4
Mean eGFR, mL/min (Hoek)	107.0 ± 23.0*	99.7 ± 20.7*	90.4 ± 29.8***	68.5 ± 22.7****
Mean 24 h SBP, mmHg	124.3 ± 12.3***	134.6 ± 14.7	141.4 ± 18.8	133.8 ± 17.4
Mean 24 h DBP, mmHg	76.2 ± 8.2**	79.1 ± 9.4*	80.3 ± 10.8*	69.7 ± 7.4
Mean 24 h PP, mmHg	49.0 ± 10.5*	55.8 ± 12.7	61.0 ± 14.5	64.1 ± 17.6
SBP night fall	6.1 ± 4.8***	6.5 ± 7.2	5.8 ± 5.5	2.9 ± 5.4
DBP night fall	9.7 ± 4.7	8.0 ± 9.5	9.5 ± 6.4	6.8 ± 6.9
Mean AASI	0.34 ± 0.16*	0.40 ± 0.16*	0.45 ± 0.17**	0.59 ± 0.12
Mean Sym-AASI	0.15 ± 0.17*	0.17 ± 0.15**	0.23 ± 0.12**	0.35 ± 0.16

Notes: Gender differences are not significant. Proportion of diabetics is not statistically significant between groups. eGFR, estimated glomerular filtration rate; MDRD, Modification of Diet in Renal Disease; SBP, systolic blood pressure; DBP, diastolic blood pressure; PP, pulse pressure; Sym-AASI, Symmetrical Ambulatory Arterial Stiffness Index.

*, **, ***, and **** denote p < 0.001 versus fourth quartile, p < 0.01 versus fourth quartile, p < 0.05 versus fourth quartile, and p < 0.05 versus mean eGFR estimated by MDRD in this quartile.

Figure 1. AASI and Sym-AASI increases as cystatin C increases (plotted by quartiles). Differences are significant (see values in Table 1).

Table 2. Multivariate linear regression: Sym-AASI versus cystatin C

	B	95% CI		p-Value
		Lower bound	Upper bound
Constant	0.060	−0.118	0.238	0.736
Age	0.006	0.005	0.008	0.000
Gender (male)	−0.054	−0.092	−0.016	0.162
Body mass index	0.001	−0.001	0.004	0.556
Waist perimeter	−0.010	−0.015	−0.005	0.045
Total cholesterol	0.001	−0.002	0.004	0.702
HDL	−0.003	−0.006	0.000	0.313
Triglycerides	−0.001	−0.003	0.002	0.827
LDL	0.000	−0.001	0.000	0.652
Cystatin C	0.129	0.066	0.192	0.044
SBP night fall	0.903	0.462	1.344	0.045
DBP night fall	−1.220	−1.572	−0.868	0.001
Treatment	−0.024	−0.063	0.015	0.540

Notes: Sym-AASI, symmetrical ambulatory arterial stiffness index; HDL, high-density lipoprotein; LDL, low-density lipoprotein; SBP, systolic blood pressure; DBP, diastolic blood pressure.

Table 3. Multivariate linear regression: Sym-AASI versus eGFR

	B	95% CI		p-Value
		Lower bound	Upper bound
Constant	0.210	0.006	0.414	0.308
Age	0.007	0.006	0.009	0.000
Gender (male)	−0.049	−0.087	−0.010	0.213
Body mass index	0.001	−0.001	0.003	0.701
Waist perimeter	−0.009	−0.014	−0.004	0.066
Total cholesterol	0.001	−0.002	0.003	0.811
HDL	−0.002	−0.005	0.000	0.388
Triglycerides	0.000	−0.003	0.002	0.908
LDL	0.000	−0.001	0.000	0.904
eGFR	−0.001	−0.001	0.000	0.269
SBP night fall	0.756	0.313	1.198	0.092
DBP night fall	−1.145	−1.501	−0.789	0.002
Treatment	−0.033	−0.073	0.006	0.402

Notes: eGFR, estimated glomerular filtration rate; Sym-AASI, symmetrical ambulatory arterial stiffness index; HDL, high-density lipoprotein; LDL, low-density lipoprotein; SBP, systolic blood pressure; DBP, diastolic blood pressure.

Table 4. Multivariate linear regression: PP versus cystatin C

	B	95%CI		p-Value
		Lower bound	Upper bound
Constant	40.624	23.063	58.184	0.024
Age	0.457	0.305	0.610	0.004
Gender (male)	−9.163	−12.913	−5.413	0.017
Body mass index	0.334	0.114	0.554	0.134
Waist perimeter	−1.024	−1.496	−0.551	0.034
Total cholesterol	−0.169	−0.423	0.085	0.507
HDL	0.028	−0.246	0.301	0.920
Triglycerides	0.186	−0.064	0.436	0.460
LDL	0.024	−0.025	0.073	0.629
Cystatin C	6.701	0.472	12.930	0.286
SBP night fall	51.856	8.220	95.493	0.239
DBP night fall	−83.216	−117.994	−48.438	0.019
Treatment	−1.737	−5.575	2.102	0.652

Notes: PP, pulse pressure; HDL, high-density lipoprotein; LDL, low-density lipoprotein; SBP, systolic blood pressure; DBP, diastolic blood pressure.