Association of acute kidney injury stages with in-hospital and long-term mortality in older adults with hip fractures.

BACKGROUND: Hip fractures and acute kidney injury (AKI) are common among older adults and are each associated with increased morbidity and mortality. We aimed to evaluate whether AKI severity is associated with increased mortality and institutionalization in older adult patients with hip fractures. METHODS: This single-centre, retrospective study included patients aged ≥65 years who underwent surgery for hip fractures. Those with stage 4 or 5 chronic kidney disease or end-stage kidney disease were excluded. AKI was defined and categorized according to the Kidney Disease: Improving Global Outcomes guideline. Patients who did not develop AKI served as the reference group for subsequent analyses. RESULTS: Overall, 661 older adults with hip fractures were included (median age: 82.0 [76.0-86.0] years, women: 76.3%). Among these, 35.9% had AKI, with 80.2, 11.8, and 8.0% classified as stages 1, 2, and 3, respectively. Thirteen patients died during hospitalization. During a median follow-up period of 4.3 (2.6-5.9) years, 301 patients died. Stage 3 AKI was associated with in-hospital mortality compared to patients without AKI (HR, 7.82 [1.21-50.72], p = 0.031). Higher AKI stages were associated with increased long-term mortality in multivariable analyses (HR, 1.32 [0.97-1.80], p = 0.076 for stage 1, HR, 2.52 [1.52-4.20], p < 0.001 for stage 2 and HR, 3.15 [1.76-5.63], p < 0.001 for stage 3). Age, men, cardiovascular disease, and low albumin level were associated with long-term mortality in patients with AKI. The proportion of institutionalization did not differ among patients across the AKI stages. CONCLUSIONS: Higher AKI stages are associated with increased in-hospital and long-term mortality in older adults with hip fractures. Preventing AKI development and progression is essential to improve prognosis in this vulnerable population.