Differences among physical activity actigraphy algorithms in three chronic illness populations.

Objectives: In three chronic illness populations and in a combined sample, we assessed differences in two algorithms to determine wear time (WT%) and four algorithms to determine: Kilocalories, light physical activity (PA), moderate-to-vigorous PA (MVPA), and metabolic equivalents (METs).

Methods: Data were collected from 29 people living with HIV (PLHIV), 27 participants recovering from a cardiac event, and 15 participants with hypertension (HTN). Participants wore the ActiGraph wGT3X-BT for 3 days on their hip. Analysis of variance (ANOVA) was used to assess differences among the algorithms.

Results: No differences were found between the two algorithms to assess WT% or among the four algorithms to assess kilocalories in each of the chronic illness populations or in the combined sample. Significant differences were found among the four algorithms for light PA ( < .001) and METs ( < .001) in each chronic illness population and in the combined sample. MVPA was significantly different among the four algorithms in the PLHIV ( = .007) and in the combined sample ( < .001), but not in the cardiac ( = .064) or HTN samples ( = .200).

Discussion: Our findings indicate that the choice of algorithm does make a difference in PA determination. Differences in algorithms should be considered when comparing PA across different chronic illness populations.