Interaction between donor and recipient age in determining the risk of chronic renal allograft failure

OBJECTIVES: Donor age is a known risk factor for chronic allograft failure (CAF) in renal transplant recipients. We have recently shown that advanced recipient age is also a risk factor for CAF. To investigate the interaction between donor and recipient age, we analyzed 40,289 primary solitary Caucasian adult renal transplants registered at the United States Renal Data System (USRDS) from 1988 to 1997. DESIGN: CAF was defined as allograft loss beyond 6 months posttransplantation, censored for death, recurrent disease, acute rejection, thrombosis, noncompliance, infection, or technical problems. Cox proportional hazards models were used to investigate the risk of allograft loss secondary to CAF. All models were corrected for 15 covariates including donor and recipient demographics, ischemic time, and human leukocyte antigen match. Donor and recipient age were categorized, and relative risk for allograft loss of the interaction between the obtained categorical covariates was evaluated. SETTING: Retrospective data analysis using the USRDS. PARTICIPANTS: All primary Caucasian renal transplant recipients from 1988 to 1997. RESULTS: Patients aged 55 and older who received donor kidneys had a 110% increased risk of CAF (relative risk (RR) = 2.1, 95% confidence interval (CI) = 1.9-2.3, P < .001) and recipients aged 65 and older had a 90% increased risk for CAF (RR = 1.9, 95% CI = 1.61-2.1, P < .001), compared with the youngest reference groups. In addition, there was an additive and, in the long term, synergistic interaction between donor and recipient age in determining allograft loss. CONCLUSIONS: Donor and recipient age had an independent, equivalently detrimental effect on renal allograft survival. An overall additive and, in the long term (beyond 36 months posttransplant), synergistic deleterious effect on renal allograft survival was observed for the interaction of donor and recipient age.