Association of Post-transplant Circulating 25-Hydroxyvitamin D and Long-term Patient and Graft Outcomes among Kidney Transplant Recipients: The Wisconsin Allograft Recipient Database (WisARD).

Background: Vitamin D inadequacy at or shortly after kidney transplantation is associated with poor outcomes. Circulating 25-hydroxyvitamin D [25(OH)D] levels generally increase over time after transplantation, but inadequacy remains common. Few studies have examined associations of later circulating 25(OH)D levels and long-term outcomes.

Methods: We analyzed data from the Wisconsin Allograft Recipient Database to assess the association of post-transplant 25(OH)D with overall graft failure, death-censored graft failure (DCGF), death with a functioning graft (DWFG), cause-specific mortality and eGFR trajectory over the next 4 years.

Results: A total of 2504 recipients who maintained a functioning graft for at least 13 months were included in our analysis. A total of 867 overall graft failures occurred during a median follow-up of 6.8 years. Vitamin D deficiency (≤20 ng/ml) was associated with a 43% higher hazard of overall graft failure (95% confidence interval [CI]: 1.16, 1.78), a 2.24-fold higher hazard of DCGF (95% CI: 1.60, 3.12) and a 2.10-fold higher hazard (95% CI: 1.37, 3.21) of infection-related mortality compared with sufficiency. It also was associated with a 1.38 ml/min/1.73m2/year faster (95% CI: -1.97, -0.79) annual eGFR decline compared with sufficiency. No association was detected for DWFG or other cause-specific mortality.

Conclusions: In conclusion, post-transplant vitamin D deficiency is associated with a higher risk of DCGF, infection-related mortality and a faster decline of graft function in kidney transplant recipients.