• Roland Schmitt, Steven Coca, Mehmet Kanbay, Mary E Tinetti, Lloyd G Cantley, and Chirag R Parikh.
• Department of Nephrology, Hannover Medical School, Hannover, Germany. schmitt.roland@mh-hannover.de
• Am. J. Kidney Dis. 2008 Aug 1;52(2):262-71.

BackgroundThe prevalence of elderly individuals continues to increase over time, as does the incidence of acute kidney injury (AKI). However, it is not known whether age is an important prognostic predictor for renal recovery after an episode of AKI.Study DesignSystematic review of MEDLINE and EMBASE databases and meta-analysis of pooled data using random-effect models.Setting & PopulationAdults with AKI, not including kidney transplant recipients.Selection Criteria For StudiesStudies published in English between 2000 and 2007 were eligible for this analysis if they met the following inclusion criteria: (1) clear definition of AKI and recovery of kidney function, (2) assessment of kidney function recovery as the primary or secondary outcome, and (3) participant age reported. We contacted the investigators of studies and requested data for recovery of kidney function by patient age.PredictorPatient age of 65 years and older and younger than 65 years.OutcomesRecovery of kidney function defined as independence from dialysis therapy, decrease in serum creatinine level to less than a defined threshold, or return to baseline kidney function.ResultsWe obtained data for recovery of kidney function by age from 17 studies of patients with AKI. Overall, 31.3% of surviving elderly patients did not recover kidney function compared with 26% of younger patients (pooled relative risk, 1.28, 95% confidence interval, 1.06 to 1.55; P < 0.05). The increased risk of nonrecovery in the elderly remained greater in several subgroups examined through sensitivity analyses, including those stratified by type of dialysis support, time of assessment of recovery (short versus long term), and definition of renal recovery.LimitationsThere was significant heterogeneity among studies with respect to comorbid factors, definition of AKI, and study design.ConclusionsThere is impaired recovery of kidney function after AKI in aged individuals. Future studies should be cognizant of "age" as a potential effect modifier in the prognosis after AKI, and clinical trials should focus on improving outcomes in the elderly cohort.

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