Overweight-mortality paradox and impact of six-minute walk distance in lung transplantation

Overweight-mortality paradox and impact of six-minute walk distance (SMWD) in lung transplantation Background: The objective of this study was to examine combined prognostic influence of body mass index (BMI) and SMWD on mortality in lung transplant recipients. Methods: Consecutive isolated lung transplant recipients were identified. Preoperative BMI and SMWD data were collected. The cohort was followed for all-cause mortality. Results: The study included 324 lung transplant recipients with mean age of 57 ± 13 years and 58% were male (27% obstructive, 3% vascular, 6% cystic fibrosis, and 64% with restrictive lung diseases). In the total cohort; 37% had normal BMI, 10% were underweight, 33% were overweight, and 20% were obese. The median SMWD was 700 feet. The lower SMWDgroup was defined as the patients who had SMWD <237 feet as determined by receiver operating characteristic (ROC). Based on this definition, 66 patients (20%) had lower SMWD. There were 71 deaths during a median follow-up of 2.3 years. In multivariate analysis, both BMI and SMWD were independently associated with death. Being overweight was associated with reduced mortality risk (hazard ratio (HR) 0.50, P = 0.042) compared to the normal BMI group, and this was primarily driven by early mortality posttransplant. This paradoxical overweight-mortality relationship remained significant in the lower SMWD group (HR 0.075, P = 0.018), but not in the higher SMWD group (P = 0.552). Conclusion: In lung transplant recipients under lung allocation score (LAS) era, pretransplant BMI and SMWD were independent predictors for mortality after the transplant. The lowest mortality risk was noted in a group of transplant recipients identified as overweight; whereas, being underweight or obese was associated with increased mortality.