Introduction: The purpose of this study was to investigate the impact, on kidney graft survival, of age and sex of the adult deceased donor, donor-recipient sex mismatch, and age and sex of the adult recipient.
Materials and Methods: The study was conducted in a single-center cohort with 6,006 kidney transplants from adult (age ≥ 18 years) deceased donors performed in adult recipients, from January 1, 2002 to December 31, 2017. There were 3,189 transplants from 18-49-year old (younger donors) and 2,817 transplants from ≥ 50-year old (older donors) donors. The recipients were divided into three age categories: 18-49, 50-59 and ≥ 60 years of age. Graft failure was defined as patient death or return to dialysis. Five-year graft survival curves were constructed with the Kaplan-Meier method and compared with log-rank test or Cox regression analysis. Statistical significance was set at p <0.05.
Results: (1) Donor and recipient age ≥ 50 years and recipient male sex, but not donor sex or donor-recipient sex mismatch, had a negative impact on 5-year graft survival, in the univariate analysis; (2) Cox regression analysis showed that donor age ≥ 50 years, recipient age between 50-59 years, ≥ 60 years, and recipient male sex were independently associated with lower graft survival, with hazard ratios (HR) of 1.41, 1.23, 1.69 and 1.13, respectively; (3) older age of the donor was associated  with poorer graft survival in transplants in 18-49-year old (HR=1.63) and in 50-59-year old (HR=1.56) recipients, but did not impact on graft survival in recipients with 60 or more years of age; (4) male sex of the recipient was a risk factor only in recipients  with 50 or more years of age that received a transplant from a younger donor: HR of 1.61, in 50-59-year old recipients, and of 1.44, in  ≥ 60-year old recipients.
Conclusion: The main findings of this study are that (a) the inferior graft survival in male than in female recipients is restricted to transplants from younger donors into ≥ 50-year old recipients and (b) there is no difference in graft survival from younger and older donors when the recipients are ≥ 60-year old. The results of this study underline the importance of analyzing combinations of age and sex of donor and recipient in order to better estimate the risks conferred by these variables. Future studies, with larger number of transplants, are warranted to confirm the finding of our study and to explore the mechanisms behind the negative effect of the older age of the donor and the male sex of the recipient on graft survival.