(202) - Evolution of the Association Between Obesity and Survival after Adult Lung Transplantation in the Lung Allocation Score Era

Abstract

s S79 Purpose: We set out to re-investigate the relationship between body mass index (BMI) and survival after lung transplant in the post-LAS era. Methods: We performed a retrospective cohort study of 9073 adults who underwent lung transplantation in the U.S. between May 4, 2005 and June 14, 2011 to examine the association between BMI and 1-yr mortality using Cox models controlling for donor and recipient factors (OPTN data). Additionally, we studied 609 Lung Transplant Outcomes Group (LTOG) study participants to examine the association between plasma leptin (highly correlated with total body adipose mass) and 1-yr mortality using similar Cox models. We also performed a cross-sectional study examining agreement between obesity determined by BMI and by % body fat using whole-body dual X-ray absorptiometry (DXA) in 142 lung transplant candidates at Columbia University and UCSF. Results: Compared to normal weight, a BMI of 30-34.9 kg/m2 was not associated with increased 1-yr mortality (adjusted HR 1.04, 95% CI 0.881.23, p = 0.64), but a BMI> 35 kg/m2 was associated with an 82% increased mortality rate (adjusted HR 1.82, 95% CI 1.24-2.66, p = 0.002, n = 104). In the LTOG cohort, there was a significant interaction (p = 0.036) between leptin level and cardiopulmonary bypass (CPB) in 1-yr survival models even after adjustment for BMI, LAS, and other factors: among those who did not undergo CPB, higher leptin levels were associated with an increased rate of death (adjusted HR 1.86 per natural log increase in leptin, 95% CI 1.08-3.20, p = 0.03), but not among those without CPB (p = 0.20). In the Columbia/ UCSF cohort, despite strong correlation between BMI and total body fat by DXA (r = 0.57, p 30 kg/m2 was only 26% sensitive for obesity by DXA. Conclusion: In contrast to the pre-LAS era, a BMI of 30 to 34.9 kg/m2 was not associated with 1-yr mortality after lung transplantation in the United States in the LAS era. Yet, the association of higher plasma leptin levels with mortality suggests that adiposity remains an important determinant of transplant outcomes. Since BMI may be a poor measure of adiposity in lung transplant candidates, alternate measures of adiposity should be explored.