Musculoskeletal Comorbidities Predict Lung Function and Mortality in Patients with Idiopathic Pulmonary Fibrosis

Abstract

Idiopathic pulmonary fibrosis (IPF) is a progressive disease associated with high mortality. Low muscle mass, frailty and sarcopenia lead to functional impairment that negatively impacts quality of life and survival but are not used in clinical practice. We aimed to determine the association between Fat-free mass index (FFMI) and frailty on lung function and exercise tolerance and survival in patients with IPF. In this study, 70 patients with IPF underwent assessment of body composition, lung function, six-minute walk distance (6MWD) testing, hand grip strength, quality of life (QoL) assessment by St. George’s Respiratory questionnaire (SGRQ) and frailty assessment using the SHARE-FI tool. FFMI was calculated using pectoralis muscle cross-sectional area (PM-CSA) on CT chest images and the lowest quartile defined reduced muscle mass. Sarcopenia was defined as low FFMI and handgrip strength. Regression analyses were conducted to determine predictive value of frailty, low FFMI and sarcopenia on clinical outcomes. The Cox proportional hazards model was used to analyze the impact of FFMI and frailty score on survival. The mean age was 70 years with moderate impairment in lung function (mean ppFVC- 68.5%, ppDLCO- 45.6%). Baseline forced vital capacity (p<0.001), diffusion capacity of lung for carbon monoxide (p=<0.01), 6WMD (p<0.05) were significantly lower in frail patients compared to non-frail patients. Frailty was a significant predictor of FVC, DLCO, 6MWD, SGRQ scores when adjusted for age, gender. Muscle mass and sarcopenia were significant predictors of FVC, DLCO, but not 6MWD or QoL scores. Frailty showed a significant association with increased mortality (HR 2.6, 95% CI- 1.1-6.7) adjusting for age and gender. These conditions may represent a continuum of musculoskeletal dysfunction and early recognition may present an area for intervention in this cohort. The effect of musculoskeletal comorbidities on patients with other interstitial lung disease is yet to be assessed.