Drew DA, et al. - Researchers assessed the links between fibroblast growth factor 23 (FGF-23) and decline in kidney function (defined by estimated glomerular filtration rate (eGFR) decline ≥30% or ≥3 mL/min/year) and incident chronic kidney disease (CKD; incident eGFR <60 mL/min/1.73 m² and ≥1 mL/min/year decline) in a cohort of well-functioning older adults from the Healthy Aging and Body Composition Study. No consistent association was observed between higher FGF-23 concentrations and decline in kidney function or incident CKD among community-dwelling older adults.

• Serum FGF-23 was assayed using an intact ELISA assay in 2,496 well-functioning older adults of the Healthy Aging and Body Composition Study.
• Cystatin C was assayed at baseline and years 3 and 10 to estimate kidney function.
• The links between FGF-23 and decline in kidney function and incident chronic kidney disease were assessed, adjusting models for demographics, baseline eGFR, urine albumin/creatinine ratio, comorbidity, and serum calcium, phosphorus, 25(OH) vitamin D and parathyroid hormone.

• Study population comprised of 52% female and 38% black, with mean (SD) age of 75 (3) years.
• Data showed 30% decline in 405 persons, >3 mL/min/year decline in 702, and incident CKD in 536.
• Doubling of FGF-23 concentrations was not shown to be related to kidney function decline (OR [95% CI] = 0.98 [0.82–1.19] for ≥30% decline and OR 1.17 [95% CI 1.00–1.37] for ≥3 mL/min/year decline), or incident CKD (incident rate ratio [IRR] 1.05 [95% CI 0.91–1.22]) in fully adjusted continuous models.
• Significant association of the highest quartile of FGF-23 with incident CKD (IRR 1.27 [95% CI 1.02–1.58] for highest vs. lowest quartile) was shown in adjusted quartile analysis.