Pretransplant Weight Loss and Poorer Posttransplant Outcomes

In patients with end-stage renal disease or earlier stages of chronic kidney disease, weight loss may signal protein-wasting malnutrition and progressive sarcopenia, as well as increased risk for mortality. Wasting measured by unintentional weight loss is a factor in physical frailty. Frailty in recipients of deceased donor kidney transplantation is associated with increased risk for delirium, early hospital readmission, longer transplant hospitalization length of stay, and post-transplant mortality.

However, according to Meera Nair Harhay, MD, MSCE, et al., there are few data available on pre-deceased donor kidney transplantation weight loss as an independent predictor of posttransplant outcomes. Dr. Harhay and colleagues conducted a retrospective cohort study to examine whether there is an independent association between weight change while awaiting deceased donor kidney transplantation and differences in transplant hospitalization length of stay and in posttransplant all-cause graft loss and risk of mortality. The researchers also sought to determine whether the association of pretransplant weight change with posttransplant outcomes was modified by patient characteristics. Results of the study were reported in the American Journal of Kidney Diseases [2019;74(3):361-372].

The outcomes of interest were (1) transplant hospital length of stay in days; (2) all-cause graft failure; and (3) mortality. The study exposures were relative pretransplant weight change as a continuous predictor and characterized as (1) <5% weight changes from wait-listing to transplant (stable weight); (2) weight loss ≥5% and <10% of listing body weight; (3) weight loss ≥10% of listing body weight; (4) weight gain ≥5% and <10% of listing body weight; and (5) weight gain ≥10% of listing body weight.

The study included 94,465 recipients of a deceased donor kidney transplant between December 4, 2004, and December 3, 2014. Median age was 54 years, 32% were black, and 60% were male. Median follow-up posttransplantation was 5.0 years. Median change in weight from listing to transplantation was 0 kg.

Weight change pretransplant was more common among recipients in the later years of the study period. Fifty-two percent (n=49,366) of recipients underwent transplant with stable weight (<5% weight change from listing to transplant); 12% (n=10,921) of recipients had lost ≥5% and <10% of their listing weight, 11% (n=10,779) had gained ≥5% and <10% of their listing weight; 14% (n=12,785) had gained ≥10% of their listing weight, and 11% (n=10,614) had lost ≥10% of their listing weight.

Those with ≥10% pretransplant weight loss were more likely to be younger than 45 years than those with <5% pretransplant weight change (33% vs 29%), more likely to be of black race (37% vs 31%), female (41% vs 37%), and have longer waiting times (median, 3.0 vs 1.8 years) (P<.001 for all comparisons). Those with <5% pretransplant weight change had similar rates of delayed graft function as those with ≥10% relative weight loss (24% vs 25%; P=.05).

There was a nonlinear unadjusted association between relative pretransplant weight change and transplant hospitalization length of stay, with a steep increase in length of stay among those with >20% relative pretransplant weight loss compared with those with no pretransplant weight change. In the complete gamma regression model, those with ≥10% pretransplant weight loss had 0.66 (95% confidence interval [CI], 0.23-1.09) days longer average transplant hospitalization length of stay compared with those with <5% pretransplant weight change (P=.003).

The association between pretransplant weight loss and transplant hospitalization length of stay was modified by pretransplant dialysis exposure, time on the transplant wait list, and listing body mass index (BMI). Age was not an effect modifier. Weight loss of ≥10% was associated with greater increased in length of stay among those with <3 years of dialysis exposure, shorter time on the wait list, and overweight or obese listing BMIs.

There was a nonlinear unadjusted association between relative pretransplant weight change and all-cause graft failure, with steep increases in graft failure among those who lost or gained ≥10% of their listing weight compared with recipients with no pretransplant change in weight. The unadjusted cumulative incidence of graft loss was highest among those who lost ≥10% of their listing weight.

In the complete case multivariable Cox model for all-cause graft loss, compared with recipients with <5% pretransplant weight change, those who lost ≥10% of their listing weight had 11% higher post-transplant graft loss (adjusted hazard ratio [aHR], 1.11; 95% CI, 1.06-1.17; P<.001); recipients who gained ≥10% of their listing weight had 6% higher graft loss (aHR, 1.06; 95% CI, 1.01-1.12; P=.02). The association between pretransplant weight loss and all-cause graft loss was not modified by recipient age, dialysis vintage, time on wait list, and listing BMI category.

There was a nonlinear association between relative pretransplant weight change and mortality, with a steep increase in mortality among those who lost ≥10% of their listing weight compared with recipients with no pretransplant weight change. In the complete case multivariable Cox model for mortality, compared with those with <5% pretransplant weight change, those who lost ≥10% of their listing weight had 18% higher posttransplant mortality (aHR, 1.18; 95% CI, 1.11-.1.25; P<.001). The association between pretransplant weight loss and mortality was not modified by recipient age, dialysis vintage, time on wait list, and listing BMI category.

The main study limitations cited by the authors were unmeasured confounders and the inability to identify volitional weight change.

In summary, the researchers said, “Among recipients who underwent deceased donor kidney transplantation in the United States from 2004 to 2014, we found that substantial pre-deceased donor kidney transplant weight loss was associated with longer transplant hospitalization length of stay and higher risks for all-cause graft loss and death. Because these associations were not modified by higher recipient listing BMI, our study suggests the need to closely monitor volitional weight loss among deceased donor kidney transplant candidates for evidence of worsening nutritional status and sarcopenia. More intensive monitoring strategies for deceased donor kidney transplant recipients who have experienced substantial pre-deceased donor kidney transplant weight loss may also be warranted.”

Takeaway Points

  1. Researchers conducted a retrospective cohort study to examine whether weight change while on the kidney transplant wait list is independently associated with differences in transplant hospitalization length of stay and in posttransplant all-cause graft loss and mortality.
  2. There was an association between ≥10% pretransplant weight loss and longer transplant hospitalization length of stay compared with <5% pretransplant weight change; the association was modified by pretransplant dialysis vintage, listing body mass index category, and time on wait list.
  3. There was also an association between >10% pretransplant weight loss and 1.11-fold higher graft loss and 1.18-fold higher mortality, compared with <5% pretransplant weight change; the association was not modified by pretransplant dialysis vintage, listing body mass index category, and time on wait list.