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

Abstract

<b><i>Background:</i></b> 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. <b><i>Objectives:</i></b> 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. <b><i>Method:</i></b> 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. <b><i>Results:</i></b> Age (HR 1.08, 95% CI [1.03–1.13], <i>p</i> < 0.01), BMI (HR 0.90, 95% CI [0.84–0.97], <i>p</i> < 0.01]), z-FFMI (HR 0.70, 95% CI [0.56–0.87], <i>p</i> = 0.02), z-BFMI (HR 0.74, 95% CI [0.57–0.96], <i>p</i> < 0.01), 6-min walk distance (6MWD) (HR 0.99, 95% CI [0.99–1.00], <i>p</i> < 0.01), percent predicted diffusing capacity for carbon monoxide (%DLco) (HR 0.93, 95% CI [0.89–0.97], <i>p</i> < 0.01), and severe malnutrition (SGA-C) (HR 6.98, 95% CI [2.00–24.27], <i>p</i> < 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. <b><i>Conclusion:</i></b> z-FFMI and severe malnutrition were significant predictors of survival in fibrotic ILD patients independent of disease severity.

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