Association Between Increased Body Mass Index, Calcineurin Inhibitor Use, and Renal Graft Survival

Objectives: Using data from the US Renal Data System, we examined the relation between body mass index and graft survival as mediated through calcineurin inhibitor use. Materials and Methods: Adult patients who received a first kidney-only transplant, with at least 6 months' survival were classified into 5 categories (underweight, normal, overweight, obese, and extremely obese) according to body mass index. Associations between calcineurin inhibitor use, body mass index categories, and outcomes were investigated. Results: Underweight and normal-weight recipients lived longer than the other 3 categories, regardless of calcineurin inhibitor use. Graft survival was significantly inferior among obese and extremely obese patients. Average graft survival was significantly higher for recipients with a normal body mass index than it was for overweight, obese, and extremely obese recipients. Risk ratio for graft failure was constant for the calcineurin inhibitor versus the noncalcineurin inhibitor group across all body mass index categories. Mean body mass index for the group with rejection episodes was similar to the group with no rejections; there was no correlation between body mass index and rejection risk. Conclusions: Increased body mass index is associated with inferior patient and graft survival, independent of calcineurin inhibitor use. Because we found no correlation between body mass index and risk of rejection, we assume that, at least after the initial 6 months, the adverse effect of obesity on graft outcome is partially mediated through nonimmunologic mechanisms. When analyzing graft and patient survival rates, we recommend that body mass index be considered a risk factor.