Acute Kidney Injury in Very Old Patients - Incidence, Severity, Risk Factors and Short-Term Outcomes.

Objective: Although old age is a risk factor for acute kidney injury (AKI), data on AKI in individuals ≥80 years is limited. We aimed to provide data on AKI incidence, severity, and outcomes, to identify risk factors of AKI and 30-day mortality in those ≥80 years.

Methods: Cohort study of 2132 patients admitted to hospital. AKI was defined and classified by extended KDIGO criteria to detect community-acquired AKI, frailty as a clinical frailty score ≥5. Primary endpoints were AKI and its stages, secondary endpoints 30-day mortality and major adverse kidney events (MAKE30), a composite of mortality, new renal replacement therapy, or serum creatinine values ≥200% of baseline, all at 30 days.

Results: Median age was 86 years. AKI was frequent (35.3%) and predominately community-acquired (80.2%). The incidence rate of AKI rose with increasing age, reaching the maximum in patients 95 years old. 48.9% of AKI patients developed stage 1, while 27.0% and 24.1% reached stages 2 and 3, respectively. Frailty was identified as an independent AKI risk factor (adjusted odds ratio (aOR) 2.42 (95% confidence intervals (CI) 1.93-3.03). 30-day mortality rate was significantly higher in AKI compared to non-AKI patients (25.4 vs. 7.6%), 44.4% of AKI patients developed MAKE30. Among others, AKI and frailty were risk factors for 30-day mortality (aOR 3.02 (95% CI 2.25-4.07) and 1.53 (95% CI 1.16-2.02)), with frailty exceeding AKI in patients ≥90 years.

Conclusions: AKI occurs frequently, increases with age, is severe and predominately community-acquired in individuals ≥80 years admitted to hospital. Frailty is a risk factor for AKI besides established factors. Very old patients with AKI more frequently died or developed a high rate of the composite endpoint MAKE30. AKI and frailty are risk factors for 30-day mortality. The effect of frailty on mortality exceeded that of AKI in nonagenarians.