Demographic, metabolic, and blood pressure characteristics of living kidney donors spanning five decades

Abstract

While cautious criteria for selection of living kidney donors are credited for favorable outcomes, recent practice changes may include acceptance of less than ideal donors. To characterize trends in donor acceptance, the Renal and Lung Living Donors Evaluation (RELIVE) Study evaluated 8,951 kidney donors who donated between 1963 and 2007 at three major U.S. transplant centers. Over the study interval, there was an increase in the percentage of donors >40 years old from 38% to 51%; donors >60 years varied between 1% and 4%. The proportion of donors with obesity increased from 8% to 26% and with glucose intolerance from 9% to 25%. The percentage of hypertensive donors was consistent (5-8%). Accepted donors ≥60 years old were more likely to have obesity, glucose intolerance, and/or hypertension compared to younger donors (p<0.0001). Our results demonstrate important trends in acceptance of older and more obese donors. The fraction of older donors accepted with glucose intolerance or hypertension remains small and for the majority includes mild elevations in glucose or blood pressure that were previously classified as within normal limits.

Figure 1. Total number of donors and relationship of donor to recipient by sex

The number of living donors increased substantially, from quartile 1 to quartile 4. There was a trend on both an absolute and percent basis for more female donors in recent years. There was a notable increase in the percentage of non-biologically related donors in the 1997–2007 quartile.

Figure 2. Characteristics of living donors by year of donation

Plots of pre-donation characteristics by year of donation with smoothed trends (loess curves) over time for each quantile (5^th, 25^th, 50^th, 75^th, and 95^th). Gray circles represent data points. The middle solid black line represents the median. The black dotted-dashed lines are the 25^th and 75^th percentiles. The black dotted lines are the 5^th and 95^th percentiles and the solid grey lines are smoothed through the minima and maxima. The slopes and significance of tests for linear trends are shown in Table 4.

Figure 3. Clustering of obesity, glucose intolerance, and hypertension*

Donors are categorized into groups based on pre-donation BMI ≥ 30 kg/m², fasting blood glucose > 100 mg/dL, and diagnosis of hypertension using Venn diagrams and compared by age (younger ≤60 years old and older >60 years old) using the chi-square test. * The overall Chi-square statistic is significant (χ² = 318.2, p < 0.0001), indicating the clustering of obesity, glucose intolerance, and hypertension differs by age category.