Ethnic and seasonal variations in FGF-23 and markers of chronic kidney disease - mineral and bone disorder

Fibroblast growth factor 23 (FGF-23) and other markers of chronic kidney disease-mineral and bone disorder (CKD-MBD) provide valuable insights into disease processes, treatment options, and patient prognosis. However, limited research has explored potential associations with ethnicity or season, particularly in multi-ethnic populations residing in high-latitude regions. We evaluated CKD-BMD markers in a diverse cohort of CKD patients, who were participants of the CAN AIM to PREVENT study. FGF-23, calcium, phosphate, 25-hydroxyvitamin D (25-OHD), and intact parathyroid hormone (iPTH) in 1,234 participants with pre-dialysis CKD (mean eGFR: 41.8±14.3 mL/min) were analyzed. Mixed-effects general linear regression models adjusted for demographic and biological factors were used to compare repeated measurements across patient groups categorized by ethnicity (East Asian, White, South Asian, Black, Southeast Asian) and seasons. Compared to other groups, White participants exhibited 8.0-18.5% higher FGF-23 levels, Black participants had 0.17-0.32 mg/dL higher calcium levels, White participants had 10.0-20.1% higher 25-OHD levels, South Asian participants had 7.3-20.1% lower 25-OHD levels, and Black participants had 22.1-73.8% higher iPTH levels, while East Asian participants ad 10.7-73.8% lower iPTH levels. Seasonal variations were also observed. FGF-23 levels were 11.9-15.5% higher in summer compared to other seasons, while calcium levels were 0.03-0.06 mg/dL lower in summer. 25-OHD levels were 5.6-10.6% higher in summer and autumn compared to other seasons. This study shows that FGF-23 and CKD-MBD markers in a Canadian pre-dialysis CKD cohort vary independently by ethnicity and season. Further research is needed to understand the reasons and clinical significance of these findings.