Table 4.

Association of c-terminal FGF23 and intact FGF23 with mean weekly change in exercise capacity over 24 weeks

	Mean weekly change in peak VO₂ over 24 weeks (ml/kg/min)	P value	Mean weekly change in 6-Minute walk distance over 24 weeks (meters)	P value

cFGF23 Models^*
Unadjusted	−0.084 (−0.200 – 0.031)	0.08	0.19 (−4.32 – 4.69)	0.86
Model 1	−0.083 (−0.199 – 0.033)	0.08	0.22 (−4.28 – 4.73)	0.88
Model 2	−0.086 (−0.203 – 0.032)	0.07	−0.09 (−4.66 – 4.48)	0.73
Model 3	−0.069 (−0.191 – 0.053)	0.17	0.97 (−3.70 – 5.64)	0.83
Model 4	−0.071 (−0.192 – 0.051)	0.16	1.40 (−3.37 – 6.16)	0.63

iFGF23 Models^*
Unadjusted	−0.135 (−0.289 – 0.018	0.05	−2.40 (−8.51 – 3.70)	0.25
Model 1	−0.133 (−0.286 – 0.021)	0.05	−2.34 (−8.45 – 3.76)	0.26
Model 2	−0.137 (−0.293 – 0.019)	0.04	−2.50 (−8.70 – 3.70)	0.24
Model 3	−0.128 (−0.290 – 0.033)	0.07	−2.32 (−8.59 – 3.95)	0.26
Model 4	−0.125 (−0.287 – 0.037)	0.08	−2.23 (−8.65 – 4.19)	0.30

Results presented as mean weekly change over 24 weeks in ml/kg/min for peak VO₂ and meters for 6-minute walk distance with 95% confidence intervals

Model 1 adjusts for age, sex, black race, and exercise modality

Model 2 adjusts Model 1 variables plus diabetes, systolic blood pressure, C-reactive protein, smoking status, body mass index, NTpro-BNP, chronotropic index, and eGFR (CKD-EPI equation)

Model 3 adjusts for Model 2 plus transferrin saturation, ferritin, hemoglobin

Model 4 adjusts for Model 3 plus randomization arm and baseline exercise capacity

Exercise modality was only included in the model when peak VO₂ was the outcome

Abbreviations: FGF23, fibroblast growth factor 23; HFpEF, heart failure with preserved ejection fraction; CI, confidence intervals; NT-proBNP, B-natriuretic peptide; eGFR, estimated glomerular filtration rate