Low body mass index in kidney transplant recipients: risk or advantage for long-term graft function?

Nutritional status is known to be a marker of overall health status and a strong predictor of patient survival in several diseases. Whereas obesity is suspected to have a negative influence on general renal transplantation outcomes, the relationship between impaired nutritional status and long-term kidney graft survival is not yet clear.

We retrospectively analyzed graft survival with a follow-up time of 5 to 12.5 years among 224 kidney transplantations. A Cox proportional hazards model was applied to estimate risk factors for loss of graft function.

The Cox model initially showed no significant influence of the body mass index (BMI) at 1 year after transplantation on the risk of transplant failure (relative risk 0.97 per BMI unit, P = .34). When the patients were divided into two groups according to BMI, a clear disadvantage was shown in terms of long-term graft survival for the groups with a low BMI. The risk of loss of transplant function increased by a factor of 1.85 (relative risk) if the BMI 1 year after kidney transplantation was less than 23 (P = .035).

These findings suggested impaired long-term kidney graft survival among patients with reduced nutritional status. This result is assumed to reflect improved immune function due to reduced nutrient availability, thus leading to reinforcement of chronic rejection processes. This assumption is consistent with the already known immunomodulatory effect of caloric restriction to mitigate T-cell activation.