AKI and Subsequent Kidney Failure With Replacement Therapy Incidence in Older Adults With Advanced CKD: A Cohort Study of United States Veterans

Rationale & objective Advanced age is a major risk factor for CKD development, which has high heterogeneity in disease progression. Acute kidney injury (AKI) hospitalization rates are increasing especially amongst older adults. Previous AKI epidemiologic analyses have focused on hospitalized populations which may bias results towards sicker populations. This study examined the association between AKI and incident kidney failure with replacement therapy (KFRT) while evaluating age as an effect modifier of this relationship. Study design Retrospective cohort study. Setting & participants 24,133 Veterans ≥65 years with incident CKD stage 4 from 2011 to 2013. Exposures AKI, AKI severity, and age. Outcomes KFRT and death. Analytical approach The Fine-Gray competing risk regression was used to model AKI and incident KFRT with death as a competing risk. A Cox regression was used to model AKI severity and death. Results Despite a non-significant age interaction between AKI and KFRT, a clinically relevant combined impact of AKI and age on incident KFRT was observed. When compared to our oldest age group without AKI, those 65-74 with AKI had the highest risk of KFRT (sHR: 14.9, 95% CI: 12.7, 17.4) whereas those ≥85 with AKI had the lowest (sHR: 1.71, 95% CI: 1.22, 2.39). Once Veterans underwent KFRT, their risk of death increased by 44%. A 2-fold increased risk of KFRT was observed across all AKI severity stages. However, the risk of death increased with worsening AKI severity. Limitations Our study lacked generalizability, was restricted to ever use of medications, and used inpatient SCr labs to define AKI and AKI severity. Conclusions In this national cohort, advanced age was protective against incident KFRT but not death. This is likely explained by the high frequency of deaths observed in this population (51.1%). Nonetheless, AKI and decreasing age are substantial risk factors for incident KFRT.