Accelerated biological aging and postoperative acute kidney injury in surgical patients: a retrospective multicentre cohort analysis of 94,006 cases

Background: While aging is closely associated with increased risk of acute kidney injury (AKI), chronological age often fails to capture the heterogeneity in biological decline among individuals. In contrast, biological age emerges as a more accurate indicator of the aging process. However, the association between accelerated biological aging and postoperative AKI remains unexplored. Therefore, this study aimed to assess the association between accelerated biological aging and postoperative AKI. Methods: We conducted a retrospective cohort study from 2015 to 2023 at three academic medical centers in China, including inpatients who underwent surgery under general anesthesia. Biological age was measured using Phenotypic Age (PhenoAge) approach. Biological aging was calculated by Phenotypic Age acceleration (PhenoAgeAccel). The primary endpoint was AKI within 7 days after surgery. Secondary endpoints included AKI stage 2 or 3 (AKI 2 +) and length of stay (LOS). Results: Among 94,006 patients (median age 62 (51-71) years, 44.0% female), 37.7% were biologically older. The incidence of AKI was 1.62 per 100 person-days. After adjustment, accelerated biological aging was significantly associated with increased risk of AKI (adjusted hazard ratio (aHR) 1.50, 95% confidence interval (CI) 1.42-1.60), AKI 2 + (aHR 2.27, 95% CI 2.06-2.50), and prolonged LOS (adjusted coefficient 1.30, 95% CI 1.06-1.55). Dose-response relationship analyses revealed a monotonic non-linear positive association between PhenoAgeAccel and the risk of AKI. Discussion: Accelerated biological aging may serve as an independent risk factor for postoperative AKI, AKI 2 +, and prolonged LOS, highlighting its potential as a target for preoperative risk stratification and intervention.