Background: As an indicator of physical and cognitive functioning in community-dwelling older adults, there is increasing interest in measuring life space, defined as the geographical area a person covers in daily life. Typically measured through questionnaires, life space can be challenging to assess in amnestic dementia associated with Alzheimer's disease (AD). While global positioning system (GPS) technology has been suggested as a potential solution, there remains a lack of data validating GPS-based methods to measure life space in cognitively impaired populations. Objective: The purpose of the study was to evaluate the construct validity of a GPS system to provide quantitative measurements of global movement for individuals with mild-to-moderate AD. Methods: Nineteen community-dwelling older adults with mild-to-moderate AD (Mini-Mental State Examination score 14-28, age 70.7 ± 2.2 years) and 33 controls (CTL; age 74.0 ± 1.2 years) wore a GPS-enabled mobile phone during the day for 3 days. Measures of geographical territory (area, perimeter, mean distance from home, and time away from home) were calculated from the GPS log. Following a log-transformation to produce symmetrical distributions, group differences were tested using two-sample t tests. Construct validity of the GPS measures was tested by examining the correlation between the GPS measures and indicators of physical function [steps/day, gait velocity, and Disability Assessment for Dementia (DAD)] and affective state (Apathy Evaluation Scale and Geriatric Depression Scale). Multivariate regression was performed to evaluate the relative strength of significantly correlated factors. Results: GPS-derived area (p < 0.01), perimeter (p < 0.01), and mean distance from home (p < 0.05) were smaller in the AD group compared to CTL. The correlation analysis found significant associations of the GPS measures area and perimeter with all measures of physical function (steps/day, DAD, and gait velocity; p < 0.01), symptoms of apathy (p < 0.01), and depression (p < 0.05). Multivariate regression analysis indicated that gait velocity and dependence were the strongest variables associated with GPS measures. Conclusion: This study demonstrated that GPS-derived area and perimeter: (1) distinguished mild-to-moderate AD patients from CTL and (2) were strongly correlated with physical function and affective state. These findings confirm the ability of GPS technology to assess life space behaviour and may be particularly valuable to continuously monitor functional decline associated with neurodegenerative disease, such as AD.

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The present study examined the relationship between multiple neuropsychological symptom validity tests (SVTs) and psychological presentation. More formally, we set out to determine if performance on neuropsychological SVTs was related to psychological symptom credibility and which specific neuropsychological SVTs were most associated with noncredible psychological presentation. Archival records from 106 litigating examinees were utilized in this study. Our results illustrate that neuropsychological SVTs are modestly related to psychological symptom credibility and that specific neuropsychological SVTs are variably associated to this end. We conclude that when multiple, but not independent, neuropsychological SVTs are employed within the context of a neuropsychological examination, they do have clinical utility as it relates to credibility of psychological presentation and these constructs do share variance reciprocally in clinically meaningful ways. When independently employed, however, the observed relationship is modest at best. Hence, to place clinical opinion on firmer scientific grounds within the context of a neuropsychological examination, multiple cognitive SVTs, in hand with psychological test instruments that include validity indexes, are essential to derive opinion that is based on science rather than faith in the instance of litigation when an incentive to manifest disability for the sake of an external reward holds probable.

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