BACKGROUND AND OBJECTIVES: AKI occurs frequently in older persons. Elevated 
circulating fibroblast growth factor-23 (FGF-23), a known marker of impaired 
mineral metabolism, may also reflect tubular dysfunction and risk of AKI. This 
study evaluated FGF-23 as well as traditional markers of kidney disease, namely 
urine albumin-to-creatinine ratio (UACR) and creatinine-cystatin C estimated GFR 
(eGFRCrCyC), as risk factors for AKI in elderly individuals.
DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS: Plasma FGF-23, UACR, and 
eGFRCrCyC were measured in 3241 community-dwelling elderly individuals in the 
Cardiovascular Health Study. Hospitalization for AKI was defined by 
International Classification of Diseases, Ninth Revision, Clinical Modification 
codes. Associations of each biomarker with AKI were evaluated using Cox 
proportional hazards models adjusted for demographics, cardiovascular risk 
factors, and biomarkers of kidney function.
RESULTS: The mean participant age was 78 years; 60% of participants were women 
and 16% were African American. The median (interquartile range) values of 
biomarkers were as follows: FGF-23, 70 RU/ml (53, 99); UACR, 8.88 mg/g (4.71, 
20.47); and eGFRCrCyC, 71 ml/min per 1.73 m(2) (59, 83). Hospitalized AKI 
occurred in 119 participants over 10.0 years of median follow-up. In fully 
adjusted analyses, compared with the lowest quartiles, the highest quartiles of 
FGF-23 (≥100 RU/ml) and UACR (≥20.9 mg/g) were associated with AKI (FGF-23: 
hazard ratio [HR], 1.99; 95% confidence interval [95% CI], 1.04 to 3.80; and 
UACR: HR, 3.35; 95% CI, 1.83 to 6.13). Compared with the highest quartile, the 
lowest quartile of eGFRCrCyC (<57 ml/min per 1.73 m(2)) was associated with AKI 
with an HR of 2.15 (95% CI, 1.21 to 3.82).
CONCLUSIONS: FGF-23 adjusted for albuminuria, cardiovascular disease risk 
factors, and baseline eGFR is independently associated with a higher risk of AKI 
hospitalizations in community-dwelling elderly individuals. Further studies to 
understand the nature of this association are warranted.