Long-Term Renal Function and Cardiovascular Disease Risk in Obese Kidney Donors

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Figure 1.
Linear regression analysis of renal function and cardiovascular disease risk factors in donors and matched two-kidney control subjects. (A) Renal function (ml/min per 1.73 m²) as calculated using the Modification of Diet in Renal Disease (MDRD) equation. (B) Systolic BP (mmHg). (C) Diastolic BP (mmHg). (D) Serum HDL level (mg/dl). (E) Ten-year Framingham Risk Score for significant cardiovascular events. Individual donor (grey circles) and two-kidney control subject (black circles) values as well as the corresponding linear regression lines (gray line: donors; black line: two-kidney control subjects) are depicted. Pearson correlation coefficient (r) is shown for each group.

Table 1.

Clinical center and study population demographics^a

Demographic	Clinical Center Population	Study Population
No. of patients	601	98
Age at donation/study (yr; mean ± SD)	40 ± 11	44 ± 11
Time since donation (yr; mean ± SD)	12 ± 4	11 ± 7
Female (%)	60	64
Race (%)
white	56	70
black	8	4
other	36	26
BMI at donation
<25.0	50	57
25.0 to 29.9	35	27
30.0 to 34.9	13	15
≥35.0	2	1

Table 2.

Current clinical characteristics of donors according to BMI at donation^a

Parameter	Entire Population	Obese at Donation	Nonobese at Donation		P^b
Parameter	Entire Population	Obese at Donation	Nonobese at F/U	Obese at F/U	P^b
n	98	16	82		NA^c
			66	16	NA^d
Age (yr; mean ± SD)	56 ± 10	56 ± 8	56 ± 10		0.893^c
			56 ± 10	54 ± 9	0.436^d
Age at donation (yr; mean ± SD)	44 ± 11	45 ± 9	44 ± 11		0.736^c
			46 ± 11	38 ± 9	0.0113^d
Female (%)	64	50	67		0.2^c
			67	69	0.873^d
Follow-up (yr; mean ± SD)	11 ± 7	10 ± 3	11 ± 7		0.439^c
			10 ± 6	15 ± 10	0.0063^d
BMI at donation (mean ± SD)	25 ± 4	32 ± 2	24 ± 3		0.0001^c
			23 ± 2	27 ± 3	0.0001^d
BMI at study (mean ± SD)	28 ± 5	36 ± 3	26 ± 4		0.0001^c
			25 ± 2	33 ± 2	0.0001^d
Donors with diabetes (n)	3	1	2		NA^c
			1	NA	NA^d
Current or previous smoker (n)	4	2	2		NA^c
			1	NA	NA^d

↵^a Nonobese = BMI <30, obese = BMI ≥30. F/U, follow-up.
↵^b Measured by ttest for continuous variables and the χ² test for categorical variables.
↵^c Comparisons between obese at donation and nonobese at donation groups.
↵^d Comparisons between nonobese at F/U and obese at F/U.

Table 3.

Current renal function in donors according to BMI at donation^a

Parameter	Entire Population	Obese at Donation	Nonobese at Donation		P^b
Parameter	Entire Population	Obese at Donation	Nonobese at F/U	Obese at F/U	P^b
Predonation GFR (ml/min per 1.73 m²; mean ± SD)	87 ± 18	87 ± 14	87 ± 19		0.972^c
			86 ± 19	95 ± 18	0.153^d
Current GFR (ml/min per 1.73 m²; mean ± SD)	63 ± 13	64 ± 13	63 ± 13		0.826^c
			63 ± 12	66 ± 18	0.353^d
% with current GFR <60	43	50	41		0.53^c
			42	38	0.719^d
Predonation 24-h urine protein excretion (mg/d; mean ± SD)	70 ± 43	80 ± 30	68 ± 45		0.407^c
			66 ± 44	78 ± 53	0.557^d
Current 24-h urine protein excretion (mg/d; mean ± SD)	119 ± 55	146 ± 62	113 ± 52		0.027^c
			112 ± 49	116 ± 66	0.814^d
% with current 24-h urine protein excretion ≥150 mg/d	22	44	18		0.03^c
			18	13	0.628^d
Current 24-h urine albumin excretion (mg/d; mean ± SD)	10 ± 12	17 ± 22	8 ± 8		0.0056^c
			8 ± 8	7 ± 7	0.84^d
% with current 24-h urine albumin excretion ≥30 mg/d	7	13	6		0.428^c
			6	8	0.84^d
Predonation serum Cr (mg/dl; mean ± SD)	0.86 ± 0.19	0.88 ± 0.19	0.86 ± 0.19		0.737^c
			0.87 ± 0.19	0.77 ± 0.13	0.104^d
Current serum Cr (mg/dl; mean ± SD)	1.11 ± 0.23	1.15 ± 0.21	1.10 ± 0.23		0.458^c
			1.10 ± 0.22	1.10 ± 0.29	0.85^d

↵^a Nonobese = BMI <30; obese = BMI ≥30. GFR calculated using the Modification of Diet in Renal Disease formula. Cr, creatinine.
↵^b Measured by ttest for continuous variables and the χ² test for categorical variables.
↵^c Comparisons between obese at donation and nonobese at donation groups.
↵^d Comparisons between nonobese at F/U and obese at F/U.

Table 4.

Current CVD risk factors in donors according to BMI at donation^a

Parameter	Entire Population	Obese at Donation	Nonobese at Donation		P^b
Parameter	Entire Population	Obese at Donation	Nonobese at F/U	Obese at F/U	P^b
SBP (mmHg; mean ± SD)	129 ± 16	137 ± 18	127 ± 15		0.0278^c
			125 ± 14	135 ± 18	0.0179^d
DBP (mmHg; mean ± SD)	82 ± 10	86 ± 9	81 ± 9		0.0451^c
			79 ± 9	87 ± 8	0.0032^d
% with hypertension^e	40	69	34		0.01^c
			32	44	0.373^d
Total cholesterol (mg/dl; mean ± SD)	203 ± 33	206 ± 26	203 ± 34		0.689^c
			201 ± 35	207 ± 31	0.522^d
HDL cholesterol (mg/dl; mean ± SD)	59 ± 17	51 ± 13	60 ± 18		0.04^c
			62 ± 18	54 ± 15	0.0911^d
% with abnormal HDL cholesterol^f	19	44	15		0.013^c
			14	19	0.613^d
10-yr FRS	5.1	6.3	5.0		0.395^c
			4.9	5.7	0.58^d

↵^a Nonobese = BMI <30; obese = BMI ≥30.
↵^b Measured by t test for continuous variables and the χ² test for categorical variables.
↵^c Comparisons between obese at donation and nonobese at donation groups.
↵^d Comparisons between nonobese at F/U and obese at F/U.
↵^e SBP >140 mmHg, DBP >90 mmHg, or known diagnosis of hypertension.
↵^f HDL < 40 mg/dl for men, <50 mg/dl for women.

Table 5.

Current clinical parameters in donors and matched two-kidney control subjects^a

Parameter	Donor BMI Category^b	Donors	Two-Kidney Control Subjects	P^c
Renal function
GFR (ml/min per 1.73 m²; mean ± SD)	Nonobese	63 ± 13	84 ± 18	0.0001
	Obese	64 ± 13	87 ± 18	0.0001
% with GFR <60	Nonobese	41.0	5.5	0.0001
	Obese	50.0	2.1	0.0001
BP
SBP (mmHg; mean ± SD)	Nonobese	127 ± 15	124 ± 20	0.251
	Obese	137 ± 18	133 ± 13	0.454
DBP (mmHg; mean ± SD)	Nonobese	81 ± 9	71 ± 11	0.0001
	Obese	86 ± 9	77 ± 10	0.003
% with hypertension^d	Nonobese	34	38	0.486
	Obese	69	62	0.61
Other CVD risk factors
Total cholesterol (mg/dl; mean ± SD)	Nonobese	203 ± 34	207 ± 36	0.351
	Obese	206 ± 26	212 ± 38	0.623
HDL cholesterol (mg/dl; mean ± SD)	Nonobese	60 ± 18	58 ± 17	0.391
	Obese	51 ± 13	50 ± 14	0.835
% with abnormal HDL cholesterol^e	Nonobese	15	24	0.066
	Obese	44	36	0.592
10-yr FRS	Nonobese	5.0	5.1	0.893
	Obese	6.3	6.5	0.881

↵^a Nonobese = BMI <30; obese = BMI ≥30. CVD, cardiovascular disease; DBP, diastolic BP; FRS, Framingham Risk Score; SBP, systolic BP.
↵^b At time of donation
↵^c Measured by t test for continuous variables and the χ² test for categorical variables.
↵^d SBP >140 mmHg, DBP >90 mmHg, or known diagnosis of hypertension.
↵^e HDL <40 mg/dl for men, <50 mg/dl for women.