Acute kidney injury does not explain sex differences in kidney replacement therapy initiation or death amongst individuals with chronic kidney disease reported to the UK Renal Registry

Background Why more males than females start kidney replacement therapy (KRT) is incompletely understood. Acute kidney injury (AKI) is a possible factor underlying sex differences in chronic kidney disease (CKD) progression, but previous studies regarding this have been inconclusive. We investigated sex differences in the association between AKI and CKD progression in UK nephrology care.

Methods This cohort study uses UK Renal Registry data. Adults with CKD stages 4/5 in 14 nephrology centres in England were followed from January 2018 to December 2021. We compared their baseline characteristics by sex and calculated cause specific hazard ratio (HR) for outcomes: time to AKI stage 2/3 (AKI2/3), initiation of chronic KRT and death by all causes.

Results A total of 15 547 patients were included. Fewer females (43.8%) were seen in renal centres than males (56.2%). During follow-up, 3909 (25.1%) AKI2/3 episodes, 3510 (22.6%) KRT initiations, and 7293 (46.9%) deaths were observed. Males were more likely than females to experience each outcome: AKI2/3 [adjusted HR 1.39, 95% confidence interval (CI) 1.31–1.49], KRT initiation (adjusted HR 1.51, 95% CI 1.39–1.65) and death (adjusted HR 1.11, 95% CI 1.05–1.16). Adjustment for AKI2/3 did not change the association between being male and the higher risk of KRT initiation.

Conclusion Being male was associated with a higher risk of AKI2/3, KRT initiation and death. Fewer females appeared in nephrology care data than expected from population CKD prevalence. However, no evidence was found to support the hypothesis that AKI2/3 explains the higher KRT initiation rates seen amongst males.