The vanishing importance of age in renal transplantation

Background. The growing number of patients awaiting a kidney transplant rai ses questions about allocation of kidneys to the elderly and about the use of elderly donors. In all reported studies analyzing the influence of age o n the outcome after renal transplantation, age is investigated as a categor ical variable. Methods. We studied age both as a categorical (Kaplan-Meier) and as a conti nuous (Cox) variable in a total of 509 cyclosporine-treated recipients of a primary cadaveric kidney graft who underwent transplantation between July 1983 and July 1997. For the Kaplan-Meier analysis, the population was divid ed into three comparably sized age groups: 17-43 years (n=171), 44-55 years (n=169), and 56-75 years (n=169). Results. Patient survival was better and graft survival censored for death was worse in the younger patients. Overall graft survival (end point was de ath or graft failure) was not significantly influenced by age. In the Cox p roportional hazards analysis, transplantation year turned out to be an impo rtant, independent variable influencing all end points. Because the influen ce was not linear, three periods were defined in which the relative risk re mained stable: 1983-1990, 1991-1993, and 1994-1997. In the second period, t he relative risk for transplant failure or death was 49% of that in the fir st period. In the third period, the relative risk had decreased to 22% of t hat in the first period. Recipient age and donor age were significant predi ctors of overall transplant failure. There was no interaction between these variables and transplantation year. Within each transplantation period, an increase in recipient age by 1 year increased the relative risk for overal l graft failure by only 1.44%. The influence of donor age followed a J-shap ed curve with a minimum at 30 years. The influence of increasing either rec ipient or donor age was counteracted by the improving results over time. Conclusion. Considering the improving results over time, there are, at this moment, no arguments for an age restriction for kidney transplant recipien ts or donors.