Reliability of real-world walking activity and gait assessment in people with COPD. How many hours and days are needed?

<bold>Introduction:</bold> Walking impairment is an important risk factor for falls, hospitalisations and mortality. Yet, guidelines still have to be defined for obtaining valid and reliable walking activity (e.g., number of steps per day) and gait (e.g., walking speed) parameters in the real world. <bold>Objectives:</bold> i) identify the minimal daily wearing time during waking hours (7h00-22h00) that constitutes a valid day; ii) identify the minimal number of valid days required to obtain reliable weekly walking activity and gait parameters in COPD. <bold>Methods::</bold> In the EU Mobilise-D study, people with COPD were asked to wear a single wearable device on the lower back, 24 hours/day for seven days. For every day, 25 walking activity and gait parameters were calculated. Minimal required daily wearing time was determined as the highest daily wearing time category (>14h as reference) not statistically significantly changing the parameters. Intraclass correlation coefficients >0.80 determined the minimal required number of valid days. <bold>Results::</bold> 3517 days from 559 people with COPD (FEV₁=54±20 %pred) were analysed. Minimal daily wearing time varied between “no minimal requirement” and >14 h (Table 1). Minimal number of valid days varied between 1 and 6 days. <bold>Conclusion:</bold> Minimal required wearing time and number of days were parameter-specific. Overall, a minimal wearing time during waking hours of >12h for ≥3 days is advised. <fig><object-id>erj;64/suppl_68/PA791/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>