Clinical Features Associated With Fatigue in People With Fibrotic Interstitial Lung Disease: Cross-Sectional Study

Fatigue significantly impacts quality of life in fibrosing interstitial lung diseases (fILDs). Oxyhaemoglobin desaturation contributes to fatigue in chronic obstructive pulmonary disease; however, this has not been investigated in fILD. This study aimed to elucidate the relationship between fatigue and clinical features, including oxyhaemoglobin desaturation, in fILD.

Participants had stable fILD with exertional desaturation (SpO₂ ≤ 88% on 6-min walk test, 6MWT). Univariate and multivariate analyses were performed with fatigue as the dependent variable and the clinical features related to fatigue as independent variables. Fatigue was assessed using the Fatigue Severity Scale (FSS). Independent variables were specified a priori using directed acyclic graphs based on previous studies: age, BMI, severity (FVC%), Dyspnoea-12 score, physical activity (mean daily steps), desaturation (nadir SpO₂ during 6MWT and during daily life), presence of corticosteroids, and obstructive sleep apnoea.

One hundred and sixteen participants were included with mean (SD) age of 70.9 (9.8), FVC% of 69.8 (16.1). Seventy-two participants (62%) had substantial fatigue (≥ 36 on FSS). Univariate analysis showed no relationship between FSS and nadir SpO₂ during 6MWT (r = -0.03, p = 0.76) or minimum SpO₂ during daily life (r = 0.04, p = 0.74). Multiple regression analyses showed associations between higher fatigue on FSS and greater breathlessness on Dyspnoea-12 (standardised beta = 0.546, p < 0.001) and lower daily steps (standardised beta = -0.188, p = 0.02).

Dyspnoea and physical activity are associated with fatigue in fILD. Exertional desaturation does not appear to contribute to fatigue in this group.

ClinicalTrials.gov Registry (URL: https://clinicaltrials.gov/study/NCT03737409).