*Purpose: The impact of obesity complications in general and dialysis populations is well described.  However, there are limited data about long-term influence of obesity in patient (pts) and graft survival following kidney transplantation. The objective of this study is to evaluate whether body mass index (BMI) affects long-term patient and graft survival post-transplant.
*Methods: All adult (>18 years at transplant) recipients of their first kidney-only transplant at our center between 1987 and 2021 were included. Patient and graft survivals were calculated from the day of transplant until the date of death, last follow up visit, or re-transplantation. BMI at transplant was analyzed as a continuous variable and as categories: <25 (n=680), 25-29 (n=682), 30-35 (n=688), and >35 (n=687). Log-rank test was used in univariate and Cox-regression in multivariate analyses.
*Results: Outcome of 2,750 transplants was analyzed. The mean follow up was 110. 3 months with 20% of pts followed for longer than 15 yrs. Death occurred in 767 pts (673 with functioning grafts). There were 561 graft losses. There were 1122 (40.7%) females and 1617 (58.3%) males. Mean age was 48.5 +/-13.93 years (range 18 to 81). Living donors were 977 (35.5%) and 1,712 (62.5%) were deceased. Most common causes of kidney failure were diabetes (19%), PCKD (9.5%), hypertension (6.7%), and glomerulonephritis (4.6%). Significantly more men were classified as obese (BMI>30) as compared to women (56 vs 42%, p<001). Obesity was slightly more prevalent in Blacks than non-Blacks (55 vs. 50%, p=.2) as were in recipients of a deceased vs. a living donor (51 vs. 48%, p=.05). We observed a gradual increase in overall mortality after transplantation with each stratum of BMI (p=.001). The survival curves appear to start splitting after 5 years post-transplant and patient survival was reduced to 47%, 42%, 37% and 36% at 15 years (p=.001). Similar results were noted for long-term graft survival [figure 1]. After adjusting for race, diabetes, and type of donor, a BMI>30 was independently associated with mortality (OR 1.19; 95CI 1.029-1.372). The same was found when BMI was analyzed as a continuous variable (OR 1.019; 95CI 1.004-1.035). BMI>30 was also associated with graft failure (OR 1.13, 95CI 1.007-1.263), with similar results when BMI was analyzed as a continuous variable (OR 1.01; 95CI 1.000-1.025).
*Conclusions: Our results indicate that BMI (especially if >30) is independently associated with long-term mortality and graft loss following kidney transplantation. New therapeutic modalities may attenuate the negative impact of obesity on transplant outcomes.

Ali Olyaei

Oregon Health & Science University

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