Obesity increases peri-operative complications in transplantation but effects on long-term kidney transplant outcomes remain controversial.

We analysed U.K transplant registry data from 1^st January 2004 to 31^st December 2010. 13167 patients were listed for the first time during 2004-10; follow-up until February 2012. 6365 (48%) patients received a first renal transplant, 4045 male, 2315 female with 5 missing data. BMI was available for 5203 (82%) and missing for 1162 (18%). During follow-up, 857 (18%) patients suffered rejection and 205 (3%) patients died. Survival analysis was done using Cox PH modelling. Initial analysis showed no difference in mortality between transplanted patients if they had their BMI recorded or not. We divided the patients into BMI bands of <=18, 18.1 -30, 30.1-35, >35.1 and missing BMI. The recipient variables analysed were age, gender, ethnicity, primary diagnosis, rejection episodes and duration of renal replacement therapy prior to transplantation and donor variables were age, gender, donor BMI band.

We analysed the data twice; missing BMI was included as a band on first analyses and excluded on the repeat. The analyses was done using 3 different models. Model 1 included all variables, plus interactions for age by gender, and gender by ethnicity. Model 2 was as Model 1, but with interactions removed; no interaction terms were statistically significant. In Model 3 donor variables were excluded. Table 1 shows results using Model 2 for analysis.

All other analyses also showed increase in HR for BMI band <=18 and reduced HR for BMI 30.1-35 and >35 though non significant

In conclusion, our study shows there is no increase in mortality or rejection in patients transplanted with higher BMI. Also patients with lower BMI seemingly do worse, though of borderline significance.

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