Age-Dependent Effects of Acute Kidney Injury on End-Stage Kidney Disease and Mortality in Patients with Moderate to Severe Chronic Kidney Disease

Introduction: Old age has been considered as a positive modifier of chronic kidney disease (CKD), but the progression of CKD is often accelerated by acute kidney injury (AKI) in older adults. This study aimed to investigate this paradoxical interplay and identify age-specific predictors of end-stage kidney disease (ESKD). Methods: This retrospective cohort included 6,101 patients with CKD stage 3B-5 followed at a single center during 2005–2018. Participants were stratified into four age groups to explore age-dependent influences on the risk of ESKD and all-cause mortality. Multivariate Cox proportional hazard regression model with competing risk analysis was used to identify predictors of outcomes. Results: During a median follow-up of 2.68 years, 1,650 (27.0%) patients developed ESKD and 541 (8.9%) patients died. The rate of ESKD decreased with advancing age, being lowest in the very old-aged (>75 years) group who displayed the slowest rate of estimated glomerular filtration rate (eGFR) decline. Multivariate Cox proportional hazard regression adjusted for competing death showed that younger ages, compared with patients aged >75 years, together with AKI episodes and several traditional risk factors were identified as predictors for ESKD. The impact of AKI episodes on ESKD development was most prominent in patients aged >75 years. These results were confirmed with subgroup analyses in patients with outcomes of different ages. Conclusion: Older adults with CKD exhibited a slower decline rate of eGFR, yet they were more likely to develop ESKD following AKI episodes. These results suggest tackling AKI is needed to prevent accelerated initiation of renal replacement therapy in elderly patients with pre-existing CKD.