Background: Previous studies have shown the importance of frailty in patients with fibrotic interstitial lung disease (ILD). We aimed to determine whether the Clinical Frailty Scale (CFS) is associated with disease progression in this population.

Methods: Patients were included from the prospective multicenter Canadian Registry for Pulmonary Fibrosis. The CFS was assessed using information from initial visits. Joint models (longitudinal mixed effect and Cox proportional hazards submodels) accounting for informative dropout due to death or lung transplant were used to compare trajectories of forced vital capacity (FVC), diffusing capacity for CO (DLCO) and 6-minute walk distance (6MWD) %-predicted in fit (CFS 1-3) vs vulnerable/frail (CFS ?4) patients over 5 years from CFS assessment.

Results: 858 patients were classified as fit (54%) and 729 as vulnerable or frail (46%). Mean age±SD was 64±12 in fit and 68±12 years in vulnerable/frail patients. FVC, DLCO, and 6MWD %-predicted at baseline were 78±20, 57±20 and 82±24 in fit vs 68±21, 45±18 and 63±22 in vulnerable/frail patients, respectively. Fit versus vulnerable/frail patients had the following mean annual change (95% CI): FVC -1.55 (-2.04 to -1.15) vs -2.12 (-3.11 to -1.24), p=0.03; DLCO -1.96 (-2.44 to -1.57) vs -2.42 (-3.48 to -1.93), p=0.20; and 6MWD -2.23 (-2.89 to -1.60) vs -3.96 (-5.69 to -2.31), p=0.001. Differences in trajectories remained similar with adjustment for age, sex, body mass index, ever smoking, ILD diagnosis, and drug treatment.

Conclusion: The simple and practical CFS might contribute to estimation of pulmonary and functional disease progression in patients with fibrotic ILD.