Background and objectiveFrailty is the age-related accumulation of deficits that decrease the ability to respond to biological stress. Patients with fibrotic interstitial lung disease (ILD) may be frail due to consequences of ILD, age, co-morbidities and adverse effects of pharmacotherapies. The objective of this study was to examine the prevalence and predictors of frailty in fibrotic ILD. MethodsFibrotic ILD patients were recruited from a specialized clinic. Patients with ILD secondary to a systemic disease were excluded. Frailty was determined using the Frailty Index based on the presence or absence of multiple deficits, including co-morbidities, symptoms and functional limitations. The Frailty Index was based on the proportion of deficits present, with frailty defined as a score >0.21. Cronbach's alpha was used to estimate the internal consistency of the Frailty Index. Dyspnoea was measured using the University of California San Diego Shortness of Breath Questionnaire. Multivariate analysis was used to determine independent predictors of frailty. ResultsThe definition of frailty was met in 50% of the 129 patients. Cronbach's alpha for the Frailty Index was 0.87. The Frailty Index was associated with forced vital capacity (FVC), forced expiratory volume in 1s (FEV1), diffusion capacity of the lung for carbon monoxide (DLCO), ILD-gender, age and physiology (GAP) index, composite physiologic index and dyspnoea score. Dyspnoea severity was the strongest unadjusted predictor (r=0.65, P<0.001) and only independent predictor of the Frailty Index (0.034 increase in Frailty Index per 10-point increase in dyspnoea score; R-2=0.37; P<0.001). ConclusionFrailty is highly prevalent and is strongly and independently associated with dyspnoea severity, demonstrating that dyspnoea is a more important determinant of frailty than pulmonary function. Fibrotic interstitial lung disease (ILD) patients were recruited from a specialized clinic to show that frailty is highly prevalent and is strongly and independently associated with dyspnoea severity. These findings suggest that frailty is an important feature of fibrotic ILD that warrants further study.