Influence of cataract surgery and blood pressure changes caused by sodium restriction on retinal vascular diameter

Figures & data

Table 1 Characteristics of the sodium restriction group and the control group

	Sodium restriction group (n = 100)	Control group (n = 100)	P value
Age (years)	78.0 ± 4.9	74.9 ± 10	0.006**
Gender
Male	48 (48%)	44 (44%)	ns
Female	52 (52%)	56 (56%)
BMI	24.0 ± 4.5	24.0 ± 4.1	ns
Hypertension
+	86 (86%)	60 (60%)	<0.001**
−	14 (14%)	40 (40%)	%
MABP (before surgery)	87.6 ± 6.9	87.1 ± 9.5	0.674
Diabetes
+	35 (35%)	36 (36%)	ns
−	65 (65%)	64 (64%)
Hyperlipidemia
+	46 (46%)	64 (64%)	0.016*
−	54 (54%)	36 (36%)	%
Current alcohol intake
+	26 (26%)	28 (28%)	ns
−	74 (74%)	72 (72%)	%
Brinkman index	65.8 ± 206.9	139 ± 289.1	0.041*
median (25th–75th)	0 (0–0)	0 (0–200)	<0.001**

Notes: Data are shown as n (%) or as the mean ± standard deviation;

* P based on the unpaired t-test (for age [Welch’s t-test], BMI, MABP, and Brinkman Index), the Wilcoxon signed rank test (for the median Brinkman Index), and the χ² test (for all characteristics, except for age, BMI, MABP, and Brinkman Index.)

* P < 0.05;

** P < 0.01.

Abbreviations: BMI, body mass index; MABP, mean arterial blood pressure; ns, not significant.

Table 2 Change in blood pressure and retinal vessel caliber before and after cataract surgery in the sodium restriction group and in the control group

		Before surgery	After surgery	Change	Percentage change	P value
Retinal arteriolar caliber (μm)	Sodium restriction group (n = 100)	140.2 ± 13.1	140.5 ± 14.0	0.3 ± 9.3	0.2%	0.732
	Control group (n = 100)	143.4 ± 17.5	144.2 ± 16.2	0.8 ± 7.8	0.6%	0.296
		Change (sodium restriction group vs control group)				ns
Retinal venular caliber (μm)	Sodium restriction group (n = 100)	211.3 ± 27.6	214.1 ± 28.7	2.8 ± 12.9	1.3%	0.031*
	Control group (n = 100)	217.4 ± 23.4	218.4 ± 24.0	0.9 ± 11.9	0.4%	0.435
		Change (sodium restriction group vs control group)				ns
MABP (mmHg)	Sodium restriction group (n = 100)	87.6 ± 6.9	83.1 ± 6.5	−4.4 ± 6.9	−5.0%	<0.001**
	Control group (n = 100)	87.1 ± 9.5	86.5 ± 8.7	−0.6 ± 6.5	−0.6%	0.397
		Change (sodium restriction group vs control group)				<0.001**
SBP (mmHg)	Sodium restriction group (n = 100)	133.5 ± 12.7	123.3 ± 11.1	−10.2 ± 16.4	−7.6%	<0.001**
	Control group (n = 100)	121.5 ± 14.9	124.4 ± 12.7	2.9 ± 16.4	2.4%	<0.001**
		Change (sodium restriction group vs control group)				<0.001**
DBP (mmHg)	Sodium restriction group (n = 100)	70.7 ± 8.8	65.9 ± 6.8	−4.8 ± 10.9	−6.8%	0.081
	Control group (n = 100)	67.0 ± 6.6	67.0 ± 6.7	−0.1 ± 8.8	−0.1%	0.946
		Change (sodium restriction group vs control group)				0.001**

* Notes: P < 0.05;

** P < 0.01. The before vs after cataract surgery association was analyzed by paired t-test. The sodium restriction group vs the control group association was analyzed by unpaired t-test; the amount of change was determined by the formula: change = after surgery – before surgery; percentage of change was determined by the formula: percentage change = (after surgery – before surgery) χ before surgery.

Abbreviations: DBP, diastolic blood pressure; MABP, mean arterial blood pressure; SBP, systolic blood pressure; ns, not significant.

Table 3 Results of single and multiple regression analyses on the association of background factors with differences in retinal arteriolar diameters before and after sodium restriction

	Single regression analysis		Multiple regression analysis model 1		Multiple regression analysis model 2		Multiple regression analysis model 3
	B	P value (95% CI)	B	P value (95% CI)	B	P value (95% CI)	B	P value (95% CI)
			−16.445	0.008** (−28.549, −4.341)	−16.418	0.008** (−28.544, −4.293)	−21.865	0.012* (−38.881, −4.850)
Group	0.817	0.343 (−0.878, 2.513)	–	–	–	–	–	–
Sodium restriction group	−0.496	0.684 (−2.894, 1.901)	−0.104	ns (−2.374, 2.165)	−0.195	ns (−2.491, 2.100)	−0.285	ns (−2.590, 2.020)
Control group	0		0		0		0
	−4.640	0.426 (−16.109, 6.830)	–	–	–	–	–	–
Age	0.068	0.369 (−0.081, 0.217)	0.140	ns (−0.008, 0.287)	0.135	ns (−0.013, 0.284)	0.146	ns (−0.004, 0.296)
Gender	−1.606	0.045* (−3.175, −0.037)	–	–	–	–	–	–
Male	4.729	<0.001** (2.416, 7.043)	1.906	ns (−0.593, 4.405)	2.053	ns (−0.501, 4.608)	2.517	ns (−0.409, 4.723)
Female	0		0		0		0
Diabetes	−0.484	0.517 (−1.957, 0.988)	–	–	–	–	–	–
+	2.968	0.019* (0.496, 5.439)	5.538	0.001** (1.613, 6.472)	5.657	0.001** (2.497, 8.817)	5.867	<0.001** (2.672, 9.062)
−	0		0		0		0
Hyperlipidemia	−0.984	0.272 (−2.748, 0.779)	–	–	–	–	–	–
+	2.825	0.020* (0.446, 5.203)	4.042	0.001** (2.410, 8.665)	4.053	0.001** (1.619, 6.487)	4.007	0.001** (1.570, 6.445)
−	0		0		0		0
Current alcohol intake	−0.624	0.369 (−1.991, 0.742)	–	–	–	–	–	–
+	4.420	0.001* (1.791, 7.050)	5.419	<0.001** (2.648, 8.191)	5.477	<0.001** (2.694, 8.261)	5.580	<0.001** (2.785, 8.374)
−	0		0		0		0
	−8.078	0.018* (−14.781, −1.376)	–	–	–	–	–	–
BMI	0.361	0.010* (0.085, 0.636)	−0.005	ns (−0.313, 0.302)	0.009	ns (−0.303, 0.321)	−0.037	ns (−0.364, 0.291)
	0.224	0.732 (−1.064, 1.511)	–	–	–	–	–	–
Brinkman index	0.003	0.161 (−0.001, 0.008)	–	–	−0.001	ns (−0.006, 0.003)	−0.002	ns (−0.006, 0.003)
	−3.807	0.556 (−16.523, 8.909)	–	–	–	–	–	–
MABP (before surgery)	0.050	0.496 (−0.095, 0.195)	–	–	–	–	0.065	ns (−0.077, 0.207)

Notes: Retinal arteriolar caliber (before – after surgery, one-week hospitalization)

* P < 0.05;

** P < 0.01. Model 1: adjusted for age, gender, diabetes mellitus, hyperlipidemia, alcohol intake, and BMI. Model 2: adjusted for age, gender, diabetes mellitus, hyperlipidemia, Brinkman Index, alcohol intake, and BMI. Model 3: a saturated model, adjusted for all factors.

Abbreviations: BMI, body mass index; CI, confidence interval; MABP, mean arterial blood pressure; ns, not significant.

Table 4 Results of single and multiple regression analyses on the association of background factors with differences in retinal venular diameters before and after sodium restriction

	Single regression analysis		Multiple regression analysis model 1		Multiple regression analysis model 2		Multiple regression analysis model 3
	B	P value (95% CI)	B	P value (95% CI)	B	P value (95% CI)	B	P value (95% CI)
			−19.500	0.018* (−35.648, −3.351)	−22.666	0.006** (−38.751, −6.58)	−14.349	0.265 (−39.671, 10.973)
Group	0.934	0.453 (−1.518, 3.386)	–	–	–	–	–	–
Sodium restriction group	1.903	0.280 (−1.564, 5.371)	−0.150	ns (−3.573, 3.273)	0.538	ns (−2.874, 3.949)	0.460	ns (−2.970, 3.890)
Control group	0		0		0		0
	−24.755	0.003** (−40.990, −8.520)	–	–	–	–	–	–
Age	0.348	0.001** (0.137, 0.560)	0.326	0.003** (0.115, 0.537)	0.358	0.001** (0.149, 0.567)	0.341	0.003** (0.117, 0.564)
Gender	2.036	0.091 (−0.330, 4.402)	–	–	–	–	–	–
Male	−0.326	0.854 (−3.815, 3.163)	−0.357	ns (−3.700, 2.987)	−1.897	ns (−5.388, 1.594)	−0.544	ns (−4.362, 3.274)
Female	0		0		0		0
Diabetes	1.835	0.096 (−0.330, 4.000)	–	–	–	–	–	–
+	0.144	0.938 (−3.490, 3.778)	–	–	–	–	−2.492	ns (−7.427, 2.262)
−	0		0		0		0
Hyperlipidemia	5.387	<0.001** (2.880, 7.893)	–	–	–	–	–	–
+	−6.365	<0.001** (−9.744, −2.985)	−5.998	0.001 (−9.393, −2.603)	−5.742	0.001** (−9.092, −2.392)	−6.575	<0.001 (−10.203, −2.948)
−	0		0.000		0		0
Current alcohol intake	2.428	0.019* (0.399, 4.458)	–	–	–	–	–	–
+	−2.009	0.312 (−5.916, 1.897)	–	–	–	–	−1.996	ns (−6.154, 2.162)
−	0		0		0		0
	1.199	0.205 (−0.659, 3.058)	–	–	–	–	–	–
Brinkman index	0.007	0.054 (0.000, 0.054)	–	–	0.009	0.009** (0.002, 0.016)	0.011	0.003** (0.004, 0.018)
	2.502	0.618 (−7.378, 12.383)	–	–	–	–	–	–
BMI	−0.026	0.901 (−0.431, 0.380)	–	–	–	–	−0.205	ns (−0.693, 0.282)
	5.795	0.536 (−12.655, 24.245)	–	–	–	–	–	–
MABP (before surgery)	−0.045	0.675 (−0.255, 0.166)	–	–	–	–	−0.011	ns (−0.222, 0.200)

* Notes: P < 0.05;

** P < 0.01. Retinal venular caliber (before – after surgery, one-week hospitalization) Model 1: adjusted for age, gender, and hyperlipidemia. Model 2: adjusted for age, gender, hyperlipidemia, and the Brinkman Index. Model 3: a saturated model, adjusted for all factors. A reference category is 0, B is the regression coefficient, and intercept B is the partial regression coefficient.

Abbreviations: BMI, body mass index; CI, confidence interval; MABP, mean arterial blood pressure; ns, not significant.