Comparison of two accelerometer filter settings in individuals with Parkinson's disease.

This study compared common free-living physical activity (PA) outcomes, assessed with the Actigraph GT3X+ accelerometer and processed with two different filter settings, in a sample of elderly individuals with Parkinson´s disease (PD). Sixty-six individuals (73.1  ±  5.8 years) with mild to moderate idiopathic PD carried an accelerometer for 7 d. Data were processed with the default filter setting and a low frequency extension filter (LFE). Significantly larger values were obtained with the LFE for mean counts and steps per day, and for minutes per day in low intensity- and lifestyle activities at moderate intensity, but not for moderate-to vigorous intensity ambulatory activities. The largest difference was observed for mean ± SD steps per day (default = 4730  ±  3210; LFE = 11 117  ±  4553). Intraclass correlation confidence intervals and limits of agreement were generally wide, indicating poor agreement. A sub-study, in which 15 individuals with PD performed a self-paced 3 min walk, demonstrated that neither filter setting differed from video-recorded steps (p ≥ 0.05). This suggests that the LFE might overestimate PA-outcomes in free-living conditions. Until new evidence supporting an extension of the lower filter-band is presented, it is recommended that the default filter setting be used when assessing PA in elderly individuals with PD.