Fat-Free Mass Index Controlled for Age and Sex and Malnutrition Are Predictors of Survival in Interstitial Lung Disease.

BACKGROUND

Literature focusing on nutritional variables and survival in interstitial lung disease (ILD) is limited by its focus on weight and BMI and has not considered body composition.

OBJECTIVES

The primary objective of this study was to examine whether body composition measures, specifically fat-free mass index z-score (z-FFMI) and body fat mass index z-score (z-BFMI), were predictors of survival in fibrotic ILD patients. The second objective was to examine if nutrition status was a predictor of survival.

METHOD: Seventy-eight outpatients diagnosed with fibrotic ILD were recruited in this cross-sectional study. Body composition data using dual frequency bioelectrical impedance analysis (BodyStat 1500MD; UK) and nutrition status using the subjective global assessment (SGA) were determined. To control for age and sex, z-FFMI and z-BFMI were calculated using population means. Participant charts were reviewed for diagnosis, age, disease severity, and exercise capacity.

RESULTS

Age (HR 1.08, 95% CI [1.03-1.13], p < 0.01), BMI (HR 0.90, 95% CI [0.84-0.97], p < 0.01]), z-FFMI (HR 0.70, 95% CI [0.56-0.87], p = 0.02), z-BFMI (HR 0.74, 95% CI [0.57-0.96], p < 0.01), 6-min walk distance (6MWD) (HR 0.99, 95% CI [0.99-1.00], p < 0.01), percent predicted diffusing capacity for carbon monoxide (%DLco) (HR 0.93, 95% CI [0.89-0.97], p < 0.01), and severe malnutrition (SGA-C) (HR 6.98, 95% CI [2.00-24.27], p < 0.01) were significant predictors of survival. When controlled for exercise capacity and disease severity, z-FFMI and severe malnutrition were significant predictors of survival independent of %DLco.

CONCLUSION

z-FFMI and severe malnutrition were significant predictors of survival in fibrotic ILD patients independent of disease severity.