Importance: Among liver transplant candidates, obesity and frailty are associated with increased risk of death while they are on the wait-list. However, use of body mass index (BMI) may not detect candidates at a higher risk of death owing to the fact that ascites and muscle wasting are seen across transplant candidates of all BMI measurements.
Objective: To evaluate whether the association between wait-list mortality and frailty varied by BMI of liver transplant candidates.
Design, setting, and participants: A prospective cohort study was conducted at 9 liver transplant centers in the United States from March 1, 2012, to May 1, 2018, among 1108 adult liver transplant candidates without hepatocellular carcinoma.
Exposures: At outpatient evaluation, the Liver Frailty Index score was calculated (grip strength, chair stands, and balance), with frailty defined as a Liver Frailty Index score of 4.5 or more. Candidates' BMI was categorized as nonobese (18.5-29.9), class 1 obesity (30.0-34.9), and class 2 or greater obesity (≥35.0).
Main outcomes and measures: The risk of wait-list mortality was quantified using competing risks regression by candidate frailty, adjusting for age, sex, race/ethnicity, Model for End-stage Liver Disease Sodium score, cause of liver disease, and ascites, including an interaction with candidate BMI.
Results: Of 1108 liver transplant candidates (474 women and 634 men; mean [SD] age, 55 [10] years), 290 (26.2%) were frail; 170 of 670 nonobese candidates (25.4%), 64 of 246 candidates with class 1 obesity (26.0%), and 56 of 192 candidates with class 2 or greater obesity (29.2%) were frail (P = .57). Frail nonobese candidates and frail candidates with class 1 obesity had a higher risk of wait-list mortality compared with their nonfrail counterparts (nonobese candidates: adjusted subhazard ratio, 1.54; 95% CI, 1.02-2.33; P = .04; and candidates with class 1 obesity: adjusted subhazard ratio, 1.72; 95% CI, 0.99-2.99; P = .06; P = .75 for interaction). However, frail candidates with class 2 or greater obesity had a 3.19-fold higher adjusted risk of wait-list mortality compared with nonfrail candidates with class 2 or greater obesity (95% CI, 1.75-5.82; P < .001; P = .047 for interaction).
Conclusions and relevance: This study's finding suggest that among nonobese liver transplant candidates and candidates with class 1 obesity, frailty was associated with a 2-fold higher risk of wait-list mortality. However, the mortality risk associated with frailty differed for candidates with class 2 or greater obesity, with frail candidates having a more than 3-fold higher risk of wait-list mortality compared with nonfrail patients. Frailty assessments may help to identify vulnerable patients, particularly those with a BMI of 35.0 or more, in whom a clinician's visual evaluation may be less reliable to assess muscle mass and nutritional status.