Differences in Mortality by Donor Sex and Age in a Multinational Cohort of Liver Transplant Recipients

Background. Prior studies assessing the association between donor sex and liver transplant outcomes showed conflicting results. We hypothesized that donor age, recipient sex, and time posttransplant modify the relationship between donor sex and mortality. Methods. First deceased donor liver transplant recipients 13 y or older recorded in the Scientific Registry of Transplant Recipients and the Collaborative Transplant Study (n = 198 856; 1988–2019) were studied. We used multivariable Cox models to estimate the association between donor sex and mortality, accounting for the modifying effects of recipient sex, donor age (13–44, 45–59, ≥60 y), and time posttransplant (<3 versus ≥3 mo). Results from cohort-specific Cox models were combined using a 2-stage individual-patient data meta-analysis. Results. Among male recipients, early posttransplant mortality was higher with female than male donors (only statistically significant with donors aged 13–44 y); subsequently, mortality was higher with female than male donors aged 13–44 y but lower with female than male donors aged 45 y or older. Among female recipients, early posttransplant mortality was lower with female than male donors (only statistically significant with donors aged 45–59 y); subsequently, there were no significant differences in mortality by donor sex. Donor sex-related differences in mortality appeared to be driven by differences in graft survival. In the first 3 mo posttransplant, absolute mortality rates were higher in the Collaborative Transplant Study compared with the Scientific Registry of Transplant Recipients. Conclusions. Donor age modifies the association between donor sex and mortality. Among male recipients, young female donors were associated with higher mortality than young male donors, but female donors older than 45 y may offer superior long-term patient survival than same-aged male donors.