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.
Keywords: cough; idiopathic pulmonary fibrosis; interstitial lung disease; physical activity.