• Test construct validity of the digital mobility outcomes in large samples of patients with COPD, MS, PD and PFF assessed under real life conditions
• Assess predictive capacity and thresholds of digital mobility outcomes for prediction of clinical outcomes, in prospective cohorts of patients with COPD, MS, PD and PFF
• Assess responsiveness to potential interventions and ability to detect changes and define minimal important difference (MID) in digital mobility outcomes in patients with COPD, MS, PD and PFF
• Characterise real-world walking behaviour in patients with COPD, MS, PD and PFF