The impact of kidney transplantation on heart failure risk varies with candidate body mass index

Abstract

Background: The relationship of body mass index (BMI) with heart failure (HF) risk before and after kidney transplant is not well described.

Methods: We examined United States Renal Data System records for 67,591 kidney transplant candidates (1995-2004) with Medicare insurance and BMI data at listing. Heart failure diagnoses were ascertained from Medicare billing claims. Body mass index was categorized per World Health Organization criteria. We modeled time-dependent associations (adjusted hazard ratio, aHR) of transplant with HF risk after listing compared with waiting in each BMI group by multivariable, stratified Cox regression. The time-dependent exposure variables partitioned relative risk of HF after transplant versus waiting into early (<or=90 days) and late (>90 days) posttransplant periods.

Results: The BMI distribution of listed candidates was as follows: 3.7% under, 40.4% normal, 32.0% over, 16.2% obese, and 7.7% morbidly obese weight. The prevalence of HF among patients awaiting transplant reached 57.4% by 3 years. Deceased-donor transplant was associated with increased early HF risk compared with continued waiting-aHRs ranged from 2.23 for normal-BMI to 2.82 for morbidly obese patients. However, transplant reduced the risk of HF in the late posttransplant period from 54% (aHR 0.46) in normal-BMI to 32% (aHR 0.68) for morbidly obese patients. Relative benefits were largest for normal-weight candidates who received live-donor transplants (aHR 0.31).

Conclusions: Heart failure risk improves in obese patients in the long term after kidney transplant, but not as much as for nonobese patients. There is need for close monitoring and for new strategies to reduce HF risk in obese patients before and after transplant.

Figure 1. Frequency of heart failure diagnoses after kidney transplant listing and after transplantation, according to listing BMI category

DD, deceased donor; HF, heart failure; LD, living donor; KT, kidney transplant

Figure 2. Early increases in heart failure risk after kidney transplant comparing to waiting, by candidate BMI and donor type. *

* Transplant modeled as a time-dependent predictor of HF after listing in stratified multivariable regression. Models were adjusted for baseline patient traits and comorbidities as listed in Tables 1 and 2. Reference groups are patients in a given BMI category who remain without transplant. BMI group by WHO: 1-Underweight (<18.5); 2-Normal weight (18.5 to <25); 3-Overweight (25 to <30); 4-Obese (30 to <35); 5-Morbidly obese (≥35).

Figure 3. Late reductions in heart failure risk after kidney transplant comparing to waiting, by candidate BMI and donor type

* Transplant modeled as a time-dependent predictor of HF after listing in stratified multivariable regression. Models were adjusted for baseline patient traits and comorbidities as listed in Tables 1 and 2. Reference groups are patients in a given BMI category who remain without transplant. BMI group by WHO: 1-Underweight (<18.5); 2-Normal weight (18.5 to <25); 3-Overweight (25 to <30); 4-Obese (30 to <35); 5-Morbidly obese (≥35).