Assessing Older Adults' Daily Mobility: A Comparison of GPS-Derived and Self-Reported Mobility Indicators

Area of Science:

• Gerontology
• Biomedical Engineering
• Data Science

Background:

• Growing interest in GPS-based mobility assessment for health and aging research.
• Lack of consensus on thresholds for GPS-derived mobility indicators like time out of home (TOH) and number of activity locations (#ALs).
• Limited knowledge regarding the validity of these GPS-based mobility indicators.

Purpose of the Study:

• To investigate the impact of spatial and temporal thresholds on the agreement between self-reported and GPS-based mobility indicators (TOH and #ALs).
• To compare daily self-reported and GPS-derived mobility indicators.
• To explore the relationship between self-reported activity event characteristics and the correspondence with GPS data.

Main Methods:

• Utilized 7 days of GPS and diary data from 35 older adults.
• Performed sensitivity analyses to evaluate various spatial (Dmax) and temporal (Tmax, Tmin) thresholds.
• Compared self-reported mobility events with GPS-derived data to assess agreement and correspondence.

Main Results:

• Optimal agreement for TOH and #ALs achieved with specific thresholds: Tmax up to 5h, Dmax 100-200m for TOH; Dmax 125-200m, Tmin 5-6min for #ALs.
• High agreement found between self-reported and GPS-based TOH indicators.
• Moderate agreement observed for GPS-derived #ALs compared to self-reported data.

Conclusions:

• The study provides evidence-based optimal threshold settings for deriving TOH and #ALs from GPS data in older adults.
• Established the validity of GPS-derived mobility indicators, showing high agreement for TOH and moderate for #ALs.
• Findings will aid future research in selecting appropriate GPS data processing parameters and understanding mobility indicator validity.