Clinical Impact of Physical Activity and Cough on Disease Progression in Fibrotic Interstitial Lung Disease

Abstract

Physical activity limitations and cough are common in patients with interstitial lung disease (ILD), potentially leading to reduced health-related quality of life. We aimed to compare physical activity and cough between patients with subjective, progressive idiopathic pulmonary fibrosis (IPF) and fibrotic non-IPF ILD. In this prospective observational study, wrist accelerometers were worn for seven consecutive days to track steps per day (SPD). Cough was evaluated using a visual analog scale (VAScough) at baseline and weekly for six months. We included 35 patients (IPF: n = 13; non-IPF: n = 22; mean ± SD age 61.8 ± 10.8 years; FVC 65.3 ± 21.7% predicted). Baseline mean ± SD SPD was 5008 ± 4234, with no differences between IPF and non-IPF ILD. At baseline, cough was reported by 94.3% patients (mean ± SD VAScough 3.3 ± 2.6). Compared to non-IPF ILD, patients with IPF had significantly higher burden of cough (p = 0.020), and experienced a greater increase in cough over six months (p = 0.009). Patients who died or underwent lung transplantation (n = 5), had significantly lower SPD (p = 0.007) and higher VAScough (p = 0.047). Long-term follow up identified VAScough (HR: 1.387; 95%-CI 1.081–1.781; p = 0.010) and SPD (per 1000 SPD: HR 0.606; 95%-CI: 0.412–0.892; p = 0.011) as significant predictors for transplant-free survival. In conclusion, although activity didn’t differ between IPF and non-IPF ILD, cough burden was significantly greater in IPF. SPD and VAScough differed significantly in patients who subsequently experienced disease progression and were associated with long-term transplant-free survival, calling for better acknowledgement of both parameters in disease management.