Physical activity cut-points for older adults using the Zio XT onboard accelerometer

Area of Science:

• Biomedical Engineering
• Physical Activity Measurement
• Gerontology

Background:

• The Zio XT monitor, an electrocardiographic device, includes an accelerometer for quantifying physical activity.
• Accurate physical activity assessment is crucial for understanding health in free-living environments, especially in older adults.

Purpose of the Study:

• To establish activity cut-points for the Zio accelerometer to estimate time spent in very light, light, and moderate-to-vigorous physical activity (VLIPA, LIPA, MVPA).
• To compare Zio's 24-hour wear protocol estimates of daily MVPA with a waist-worn accelerometer's waking-wear protocol.

Main Methods:

• Participants (n=381) from the ARIC study simultaneously wore Zio and waist-worn ActiGraph GT3X devices.
• Physical activity was summarized using Mean Amplitude Deviation (MAD) for Zio and Vector Magnitude Counts (VMC) for GT3X.
• GT3X VMC cut-points were mapped to Zio MAD using a quantile-quantile approach.

Main Results:

• Mapped Zio MAD cut-points for VLIPA, LIPA, and MVPA were 9.04, 28.2, and 58.1 mili-g, respectively.
• Zio and GT3X showed strong correlations (ICC > 0.7) for daily activity intensity when wear time overlapped.
• MVPA estimates showed high agreement (ICC = 0.77) between devices using their respective wear times; Zio reported more LIPA and VLIPA.

Conclusions:

• Recommended cut-points for Zio accelerometry in clinical research involving older adults.
• Zio accelerometry provides reliable physical activity intensity data comparable to traditional waist-worn devices.