Validity of activity monitors for physical activity assessment in patients with chronic obstructive pulmonary disease

Rationale: Physical inactivity (PA) and symptoms during PA are hallmarks of COPD. Adequate assessment of PA is a challenging objective in COPD. Various activity monitors are available but the validity of these monitors is poorly established. We aim to evaluate the validity of six activity monitors in patients with COPD against active energy expenditure (AEE) measured with doubly labelled water (DLW). Methods: Eighty patients with COPD (age 68±6 years, FEV 1 57±19% predicted) recruited in four centres each wore simultaneously four out of six available monitors validated in chronic conditions (Lifecorder Plus, ActiWatch Spectrum, RT3, Actigraph GT3X, DynaPort MoveMonitor and SenseWear Armband) during wakefulness for 14 consecutive days. AEE was calculated (0.9xTotal Energy Expenditure (TEE) [DLW]-resting metabolic rate) and the validity of the monitors was evaluated by correlations between AEE and monitors outputs and through multiple regression analysis using TEE as the dependent variable with total body water (TBW) plus several PA monitors outputs as independent variables. Results: Except for the Lifecorder Plus and the RT3, the remaining four monitors met the validation criteria. Actigraph GT3X and DynaPort MoveMonitor explained the majority of the TEE variance not explained by TBW (53% and 70% respectively) and showed significant correlations with AEE (r=0.63 p Conclusions: The present findings should guide users in choosing valid activity monitors for research or for clinical use in patients with chronic diseases such as COPD. Funded by The Innovative Medicine Initiative Joint Undertaking (IMI JU # 115011).