Abstract
Withdrawal from activity can be challenging to assess due to the nature of amnesia associated with Alzheimer's disease (AD). GPS can capture the geographical area a person covers in daily life, or lifespace, as a proxy measure of voluntary and social activity. The purpose of the study was to examine the utility of GPS to measure lifespace in older adults with mild AD. We hypothesized that lifespace parameters (time and distance away from home, area covered) would be reduced in AD compared to healthy older adults. Nineteen community-dwelling older adults with mild AD (MMSE=14-28, age=70.7±2.2y) and 35 controls (CTL, age=74.0±1.2 y) wore a GPS-enabled smartphone during the day for 3 days. Time away from home was calculated as the percentage of time spent outside a 25m radius of their home coordinates. Mean distance was measured as the average distance from home. Area covered was determined by computing the area of the convex hull of the GPS data for each participant. All measures were log10 transformed to produce a parametric distribution and tested for group effect using 2-sample t-tests. We found that lifespace size is smaller in the AD group, indicated by lower mean distance from home and area covered. However, we did not find significant group difference in time away from home. Our preliminary findings suggest that GPS data can provide insight into spatial and temporal patterns of activity, and can potentially be used as an outcome measure of treatment intervention.Acknowledgments: We acknowledge the contributions to Alicia Capobianco and Teresa Wu in collecting data. This work was funded by a grant from the Alzheimer's Association. J. Tung was funded by the Alzheimer's Association of Canada.