Fibroblast Growth Factor 23 and Anemia in the Chronic Renal Insufficiency Cohort Study

Anemia is an early complication of CKD that is associated with increased morbidity and mortality. Prior data show associations between abnormal mineral metabolism markers and decreased erythropoiesis. However, few studies have investigated elevated fibroblast growth factor 23 as a risk factor for the development of anemia in patients with CKD.

We conducted a prospective cohort study of 3869 individuals with mild to severe CKD enrolled in the Chronic Renal Insufficiency Cohort Study between 2003 and 2008 and followed through 2013. We hypothesized that elevated baseline fibroblast growth factor 23 levels are associated with prevalent anemia, decline in hemoglobin over time, and development of incident anemia, defined as serum hemoglobin level <13 g/dl in men, serum hemoglobin level <12 g/dl in women, or use of erythropoietin stimulating agents.

In the 1872 of 3869 individuals who had prevalent anemia at baseline, mean age was 58 (11) years old, and mean eGFR was 39 (13) ml/min per 1.73 m². Higher levels of fibroblast growth factor 23 were significantly associated with prevalent anemia (odds ratio per 1-SD increase in natural log-transformed fibroblast growth factor 23, 1.39; 95% confidence interval, 1.26 to 1.52), decline in hemoglobin over 4 years, and risk of incident anemia (hazard ratio per 1-SD increase in natural log-transformed fibroblast growth factor 23, 1.13; 95% confidence interval, 1.04 to 1.24; quartile 4 versus quartile 1: hazard ratio, 1.59; 95% confidence interval, 1.19 to 2.11) independent of demographic characteristics, cardiovascular disease risk factors, CKD-specific factors, and other mineral metabolism markers. The results of our prospective analyses remained unchanged after additional adjustment for time-varying eGFR.

Elevated fibroblast growth factor 23 is associated with prevalent anemia, change in hemoglobin over time, and development of anemia. Future studies are needed to elucidate the mechanisms for these associations.