Background
Risk for acute kidney injury (AKI) in older adults has not been systematically evaluated. We sought to delineate the determinants of risk for AKI in older compared to younger adults.
Study Design
Retrospective analysis of patients hospitalized in July 2000–September 2008.
Setting & Participants
We identified all adult patients admitted to an intensive care unit (ICU) (n=45,655) in a large tertiary care university hospital system. We excluded patients receiving dialysis or kidney transplant prior to hospital admission, and patients with baseline creatinine ≥ 4 mg/dl, liver transplantation, indeterminate AKI status, or unknown age, leaving 39,938 patients.
Predictor
We collected data on multiple susceptibilities and exposures including age, sex, race, body mass, comorbid conditions, severity of illness, baseline kidney function, sepsis, and shock.
Outcomes
We defined AKI according to KDIGO (Kidney Disease: Improving Global Outcomes) criteria. We examined susceptibilities and exposures across age strata for impact on development of AKI.
Measurements
We calculated area under the receiver operating characteristic curve (AUC) for prediction of AKI across age groups.
Results
25,230 patients (63.2%) were aged 55 years or older. Overall 25,120 patients (62.9%) developed AKI (69.2% aged 55 years or older). Examples of risk factors for AKI in the oldest age category (75 years or older) were drugs (vancomycin, aminoglycosides, nonsteroidal anti-inflammatories), history of hypertension (OR, 1.13; 95% CI, 1.02–1.25) and sepsis (OR, 2.12; 95% CI, 1.68–2.67). Fewer variables remained predictive of AKI as age increased and the model for older patients was less predictive (p<0.001). For the age categories 18–54, 55–64, 65–74, and 75 years or older, the AUCs were 0.744 (95% CI, 0.735–0.752), 0.714 (95% CI, 0.702–0.726), 0.706 (95% CI, 0.693–0.718), and 0.673 (95% CI, 0.661–0.685), respectively.
Limitations
Analysis may not apply to non-ICU patients.
Conclusions
The likelihood of developing AKI increases with age; however the same variables are less predictive for AKI as age increases. Efforts to quantify risk for AKI may be more difficult in older adults.