Introduction:

The impact of obesity (body mass index [BMI] > 30 kg/m[sup2]) on kidney allograft outcomes is controversial. Recent studies found that obesity does not increase graft loss and mortality. This discrepancies probably lie on the fact that BMI integrates two components, the fat mass and the skeletal muscle mass (MM). Moreover, low MM seems to have a negative impact on kidney allograft outcomes. Here, we want to identify the role of MM on renal transplant long-term outcomes in obese patients.

Methods: All transplant recipients with a functioning graft more than one year between 1996 and 2010 in Montpellier University Hospital (France) were eligible. Mortality and death censored graft loss were recorded until June 2016. BMI was assessed at one year. In order to assess MM according to Schutte's equation, we used 24 hours urine creatinine excretion at one year post-transplantation. Cox models were used to analyze patients and death censored graft survival. We first analyzed the impact of the three groups of BMI (<18.5, 18.5-30, >30 kg/ m[sup2]) on graft outcomes. Then, the effect of MM was evaluated using tertile of MM stratified for sex. Finally, in order to measure the effect of MM in obese recipients, we split each group of BMI into two groups: low and high MM stratified for sex, according to the median of MM.

Results: We included 689 renal transplant recipients (age 49 +/- 54 years, 64.7% men); 71 recipients were obese. During follow up of 126 +/- 47.27 months, 70 recipients died and 84 lost their graft. BMI > 30 kg/m[sup2] was not predictive of renal transplant outcomes. Low MM was predictive of mortality (1^st vs. 2^nd tertile Hazard Ratio [HR]: 1.84 – confidence interval [CI] 95% [1.03-3.28]; p=0.04) but was not predictive of graft loss. In obese recipients, low MM was an independent risk factor for mortality compared to patients with BMI between 18.5 and 30 kg / m[sup2] with high MM (reference group) (HR: 4.8 – CI 95% [1.74 to 13.26]; p = 0.003). The risk of graft loss was not increased in obese recipients with low MM.

Conclusion: Our results suggest that low MM in obese renal transplant patients exposes to an increased mortality risk without increasing the risk for graft loss.

CITATION INFORMATION: Souweine J, Le Quintrec M, Szwarc I, Pernin V, Mourad G, Cristol J, Serre J. Muscle Mass Is Predictive of Mortality in Obese Renal Transplant Patients. Am J Transplant. 2017;17 (suppl 3).

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