Nonlinear Relationship Between Body Mass Index and Liver Transplant Outcomes: A Dose-Response Meta-Analysis

Background. Weight management was recommended to have more access to transplantation and improve transplant outcomes after liver transplantation (LT). However, the dose-response relationship between body mass index (BMI) and transplant outcomes has not been clearly defined. Methods. PubMed, Embase, Web of Science, and Cochrane Library databases were searched up to October 20th, 2019. Dose-response meta-analyses was conducted to establish the dose-response relationship pattern. Results. Twenty-three observational studies were eligible. In the pair-wise analysis, compared with normal BMI, HRs in underweight, overweight, obesity-I, obesity-II, and obesity-III were 2.13, 0.96, 1.06, 1.36, and 1.97 for patient death, and 3.08, 1.02, 1.25, 1.58, and 2.90, for graft loss. In the dose-response analysis, U-shaped relationships were observed between BMI and both patient and graft survival (P < .001, P < .001). Referring to 17.5kg/m(2), the patient death risk decreased to 0.72 (95% CI: 0.62-0.84) in 27kg/m(2) and then increased to 1.44 (95% CI:1.09-1.90) in 28.7-42kg/m(2). Comparing to 17.5kg/m(2), individuals in 26.7-28.0kg/m(2) had the least risk of graft loss with HR of 0.62 (95% CI:0.48-0.80) and increased to 1.64 (95% CI:1.03-2.61) in 42kg/m(2). Subgroup analyses by age, sex, sample size, duration of follow-up, location, publication year, and study type presented similar results. Conclusion. Underweight and severe obesity are associated with a significantly increased risk of graft loss and patient death after liver transplantation. Overweight, especially BMI of 26-28 kg/m(2), may have extra survival benefit. Weight management before liver transplantation may be necessary.