Study shows BMI has limited impact on post-transplant outcomes
A study of more than 300,000 kidney transplant recipients shows that BMI, often used by transplant programs to help determine eligibility, may have limited impact on outcomes.
“BMI is a well-established risk factor for transplant outcomes, and high BMI is a commonly used relative contradiction used for patient eligibility,” Jesse Schold, PhD, and colleagues from the department of quantitative health sciences at the Cleveland Clinic wrote in their abstract. Their work was presented during the virtual American Transplant Congress. “However, BMI is a relatively coarse measure for health status and the clinical impact, and risk associated with BMI levels may be varied by other patient comorbidities and demographic characteristics.”
Researchers reviewed data from the Scientific Registry for Transplant Recipients (SRTS) that included approximately 300,000 adults who received a solitary kidney transplant from 2000-2019. They charted BMI levels pre-transplant and compared these to outcomes for recipients. The team used interaction terms and stratified analyses based on demographic, clinical and donor characteristics.
“We tested for significant relative differences of BMI on overall graft loss and patient death,” the researchers wrote.
Results showed that, in the overall SRTR-extracted population, BMI “demonstrated a significant ‘J-shape’ risk profile with elevated risks for overall graft loss among low BMI recipients (BMI < 20kg/m2) and an increased risk among obese and morbidly obese recipients.
“However, using multivariable models with interaction terms with BMI, several factors significantly modified the effects of BMI, including age, diabetic status and race,” the researchers wrote. Obesity did have a more significant influence among younger recipients “which attenuated with age and shifted to a marked risk for low weight among recipients [60 years old and older]. Similar differential effects included a significantly lower risk of obesity among African Americans relative to Caucasians, lower risk of obesity among diabetics relative to non-diabetics and a higher risk associated with obesity with lower quality [higher kidney donor profile index (KDPI)] donors.”
Specifically, in reviewing kidney transplant recipients aged 18-39, Schold said “the effects of obesity for this population is relatively similar to all other [transplant] recipients. However, at low BMI levels, there is no additional risk and in fact appears somewhat protective compared to other recipients in the population.” For the age group 60-69, the effects of obesity “are somewhat attenuated compared to other [transplant] recipients, whereas the effects of low BMI is similar compared to other recipients.”
Male recipients also had a higher effect of obesity and had lower BMIs compared to female recipients.
Schold and colleagues concluded that the results show a highly variable association of BMI with post-transplant outcomes for kidney transplant recipients which “may be important to incorporate to optimize care and stratify risk." In addition, they suggest that "contraindications to transplant should not be guided by absolute BMI cutoffs but rather personalized to other transplant characteristics."