Sex and Mortality Risk in Patients Following Failure of a Kidney Transplant.

Rationale & objective: Female patients treated with dialysis experience poorer health outcomes compared with male patients, but few studies have examined sex differences in all-cause and cause-specific death after return to dialysis after failure of a kidney allograft. This study examined the association between sex and mortality after kidney allograft loss.

Study design: Retrospective cohort study.

Setting & participants: Patients in Australia and New Zealand represented in the Australia and New Zealand Dialysis and Transplant Registry (ANZDATA), who returned to dialysis after loss of their first kidney allograft between 2000 and 2020.

Exposure: Sex.

Outcome: All-cause and cause-specific mortality on dialysis through 2020.

Analytical approach: Flexible parametric survival models that integrated restricted cubic splines to examine the association between sex and mortality after kidney allograft loss. Models included sex by follow-up time interaction to examine whether these associations change over time. Follow-up was censored at the time of repeat transplantation.

Results: Of 4,135 patients who lost their first kidney allografts, 1,576 were female (38%). During a median follow-up of 2.7 (IQR, 1.1-5.4) years, 1,476 patients (36%) died on dialysis. Cardiovascular disease (CVD) and dialysis withdrawal were the most common causes of death. Compared with female patients, male patients were less likely to die early after allograft loss, with adjusted HR at 1 year after allograft loss for all-cause mortality of 0.84 (95% CI, 0.70-0.99). The reduced risk of death was attributed to infection and dialysis withdrawal, with adjusted HRs at 1 year after allograft loss of 0.58 (95% CI, 0.35-0.96) and 0.68 (95% CI, 0.47-0.99), respectively. However, we did not observe any significant sex-based differences in all-cause or cause-specific mortality beyond 1 year after allograft loss.

Limitations: Observational study, residual and unmeasured confounding factors.

Conclusions: After kidney allograft loss, female patients experienced a higher initial mortality risk compared with male patients, attributed to early deaths from infection and dialysis withdrawal.

Plain-language summary: Sex and gender are known to impact the risk of health outcomes in dialysis patients. In this study, we examined the relationship between sex differences and mortality after the failure of a kidney transplant that necessitated a return to maintenance dialysis. The study examined registry data from 4,135 patients in Australia and New Zealand who returned to dialysis after their first kidney transplant failed between 2000 and 2020. Compared with female patients, male patients were less likely to die early after allograft loss. The reduced risk of death was attributed to infection and dialysis withdrawal. We did not observe any significant sex-based differences in all-cause and cause-specific mortality beyond 1 year after allograft loss.