Racial disparities in weight gain after renal transplantation.

Renal transplantation has a profound effect on body weight by increasing body mass index in all patients after transplantation. The study reported by Baum et al.1 examines the predictors of weight gain in a cohort of racially diverse kidney transplant recipients. This multivariate analysis of the risk factors associated with cardiovascular disease showed that young overweight black women receiving grafts from related living donors with good posttransplant renal function had greater likelihoods of gaining weight. Renal transplantation accelerates the atherogenic process, and cardiovascular disease accounts for 40% of deaths after transplantation. Immunosuppressive medications in combination with the atherogenic risks associated with chronic renal failure likely interact to accelerate the atherogenic process. More than 90% of patients develop one or more of the classic cardiovascular risk factors after renal transplantation. 2 Known cardiovascular risk factors after renal transplantation are sex, hyperlipidemia, hypertension, diabetes, and obesity. Baum et al. examined those factors as putative causes of the increased mortality rate in blacks after renal transplantation and found decreased survival after transplantation. This brings up some interesting questions regarding the racial disparities in outcome. Posttransplantation diabetes occurs in up to 20% of transplant patients. Baum et al. showed that the development of diabetes is greater in black renal transplant recipients with high body mass indexes and that initial body mass index has a strong influence on the development of diabetes. The association between ethnicity and diabetes has been confirmed in other studies. In the Atherosclerosis Risk in Communities Study, diabetes incidence per 1000 person-years was about 2.4-fold greater in black women and about 1.5-fold greater in black men than in their white counterparts. 3 In that study, adiposity accounted for 47.8% of the excess risk in black women. It is not surprising that the association between ethnicity and adiposity as a risk factor for the development of diabetes was found in renal transplant patients. The profile of established risk factors for weight gain, e.g., diet and physical activity, is clearly worse in blacks than in their white counterparts, 4 but whether behavioral factors are a proxy for other factors intertwined with ethnicity is unclear. The racial disparities have been reported in health care outcomes for many diseases,5 including renal disease. There is a racial disparity in the delivery of renal dialysis, and racial minority participants are more likely to wait longer for renal transplantation.6 Even after receiving transplantation, blacks have higher rates of graft rejection than do whites, 7 with a graft failure rate 1.8 times that of whites.8 It is difficult to interpret the racial disparities after renal transplantation because race is a complex marker for sociocultural and historical factors. The increased susceptibility of blacks to weight gain after renal transplantation probably represents a complex interplay of genetic, cultural, and environmental influences. We must be careful in interpreting the factors that contribute to outcome in multivariate analyses because residual confounding of the unmeasurable factors are difficult to measure. Therefore, the residual excess risk of weight gain after renal