Background and objective: Detailed body composition, such as fat-free mass, has not been examined in idiopathic pulmonary fibrosis (IPF). We investigated whether the fat-free mass index (FFMI), an index of lean body mass, predicted survival.
Methods: Forty-four patients with IPF were enrolled in the study. Their body composition was assessed using direct segmental multi-frequency bioelectrical impedance analysis. The degree of correlation between variables of body composition and other variables such as forced vital capacity (FVC) and survival was examined.
Results: There was a significant positive correlation between FFMI and FVC, diffusion capacity of the lung for carbon monoxide (DLCO ) and 6-min walk distance, and a significant negative correlation with age. However, there was no significant correlation between FFMI and percentage predicted FVC or DLCO , with the degree of correlation being similar to that observed for BMI. The mean observation period in the survival analysis was 837.5 ± 407.5 days. A univariate Cox proportional hazard model showed that several variables, but not BMI, were associated significantly with survival. FFMI (hazard ratio (HR): 0.64, 95% CI: 0.43-0.94, P = 0.02) and percentage predicted FVC (HR: 0.96, 95% CI: 0.93-0.99, P=0.008) were significant factors in a multivariate model.
Conclusion: We conclude that FFMI is a significant independent predictor of survival in patients with IPF.
Keywords: body composition; fat-free mass; idiopathic pulmonary fibrosis; survival.
© 2016 Asian Pacific Society of Respirology.