Duration of acute kidney injury predicts 90-day mortality and chronic kidney disease progression in elderly patients

Background: This study evaluated the prognostic impact of acute kidney injury (AKI) duration on 90-d mortality and new-onset chronic kidney disease (CKD) progression in elderly patients. Methods: We retrospectively enrolled elderly patients ( >= 75 years; n = 693) from the Chinese PLA General Hospital between January 1, 2007 and December 31, 2018. The 2012 Kidney Disease Improving Global Outcomes (KDIGO) defined serum creatinine (Scr) criteria were used to identify and classify AKI. Patients were divided into transient AKI (T-AKI) and persistent AKI (P-AKI) groups based on whether Scr levels returned to baseline within 48 h post-AKI. We further classified P-AKI based on AKI duration: (1) short duration: resolving AKI lasting 3-4 days; (2) medium duration: resolving AKI lasting 5-7 days; and (3) long duration: AKI lasting > 7 days. Results: Among patients, 62 (9.0%) had T-AKI (1-2 days), 104 (15.0%) had short-duration, 140 (20.2%) had medium-duration, and 387 (55.8%) had long-duration. In total, 209 (30.2%) died within 90 days; 122 (25.2%) developed CKD. After adjusting for multiple covariates, duration of AKI (3-4 days: hazard ratio [HR] = 2.512; P = 0.045; 5-7 days: HR = 3.154; P = 0.015; > 7 days: HR = 6.212; P < 0.001) was significantly associated with a higher 90-day mortality. Longer AKI duration (3-4 days: odds ratio [OR] = 0.982; P = 0.980; 5-7 days: OR = 1.322; P = 0.661; > 7 days: OR = 7.007; P < 0.001) was significantly associated with new-onset CKD of survivors. Conclusion: AKI duration is useful for predicting poorer clinical outcomes in elderly patients, emphasizing the importance of identifying an appropriate treatment window for early intervention.