Sex Disparities in Access to Second Kidney Transplantation among Adolescents

Background: Prior work has demonstrated disparities in access to kidney transplantation by sex, with women being less likely to receive a first transplant compared to men. We aimed to determine whether this disparity persists in relation to access to second kidney transplantation. Methods: We performed a retrospective cohort study of people ≥13 years with first graft failure from 2006-2019 according to the United States Renal Data System. Using Cox proportional hazards models, the primary predictor was sex and the primary outcome was receipt of a second transplant overall, living, or deceased donor transplantation. We tested for interaction between age at first graft failure and sex. Results: Of the 36,215 individuals included, median age at first graft failure was 48 years (IQR 37-58 years; 59% male). Median vintage of the first graft was 8 years (IQR 4-13 years), with no difference by sex (p=0.44). Over the observation period, 6,935 individuals (19%) died prior to second transplant receipt, and 18,610 individuals (51%) received a second transplant. There was an interaction between age and sex (pint<0.05) such that girls 13-<18 years at first graft failure had reduced access to second transplant as compared to same-aged boys (HR 0.65, 95% CI 0.55-0.76). This relationship was not observed among older age groups. Findings were more prominent for deceased (vs living) donor transplantation in the adolescent age group. Conclusion: Adolescent girls had substantially reduced access to second transplant compared to adolescent boys, a disparity that was not observed in other age groups. Given the high priority of children on the national waitlist, further studies are needed to understanding the sources of this disparity. Funding: NIDDK Support Hazard of second kidney transplant by sex, stratified by age at first graft failure - Hazard and 95% CI for women vs. men (reference) Any transplantation Living donor transplantation Deceased donor transplantation Overall 1.02 (0.99-1.05) 1.06 (1.01-1.11) 1.00 (0.97-1.03) 13-<18 years 0.65 (0.55-0.76) 0.89 (0.64-1.24) 0.59 (0.49-0.72) 18-<40 years 1.05 (1.00-1.11) 1.05 (0.96-1.13) 1.06 (1.00-1.13) 40-<65 years 1.04 (1.00-1.08) 1.09 (1.02-1.16) 1.01 (0.97-1.06) ≥65 years 0.92 (0.83-1.00) 0.94 (0.78-1.13) 0.91 (0.81-1.02) Models adjusted for age and body mass index at first graft failure, sex, race/ethnicity, neighborhood income, calendar period (before vs. after 2014 Kidney Allocation System changes were made), insurance type, ABO blood group, and comorbidities.