Department of Kinesiology, University of Waterloo, Waterloo, Ont., Canada.
Gerontology. 2014;60(2):154-62. doi: 10.1159/000355669. Epub 2013 Dec 12.
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.
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.
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.
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.
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.
生活空间作为社区居住的老年人身体和认知功能的指标，人们越来越感兴趣于测量生活空间，其定义为一个人在日常生活中所覆盖的地理区域。生活空间通常通过问卷进行测量，但在与阿尔茨海默病（AD）相关的遗忘型痴呆症患者中，评估生活空间具有挑战性。虽然全球定位系统（GPS）技术已被提议作为一种潜在的解决方案，但在认知障碍人群中，仍缺乏验证基于 GPS 的方法来测量生活空间的相关数据。
本研究旨在评估 GPS 系统在评估轻度至中度 AD 患者的全局运动方面的构建效度。
19 名患有轻度至中度 AD 的社区居住的老年人（简易精神状态检查评分 14-28 分，年龄 70.7±2.2 岁）和 33 名对照组（CTL；年龄 74.0±1.2 岁）在白天连续 3 天佩戴具有 GPS 功能的手机。从 GPS 日志中计算出地理区域（面积、周长、离家平均距离和离家时间）等测量指标。在对数据进行对数转换以产生对称分布后，使用两样本 t 检验检验组间差异。通过检查 GPS 测量值与身体机能指标（每日步数、步态速度和痴呆残疾评估（DAD））和情感状态（淡漠评估量表和老年抑郁量表）之间的相关性，来测试 GPS 测量值的构建效度。采用多元回归分析来评估具有显著相关性的因素的相对强度。
与 CTL 相比，AD 组的 GPS 测量面积（p＜0.01）、周长（p＜0.01）和离家平均距离（p＜0.05）均较小。相关性分析发现 GPS 测量的面积和周长与身体机能的所有测量指标（每日步数、DAD 和步态速度；p＜0.01）、淡漠症状（p＜0.01）和抑郁（p＜0.05）呈显著相关。多元回归分析表明，步态速度和依赖性是与 GPS 测量值相关性最强的变量。
本研究表明，GPS 测量的面积和周长：（1）可区分轻度至中度 AD 患者与 CTL；（2）与身体机能和情感状态密切相关。这些发现证实了 GPS 技术评估生活空间行为的能力，可能特别有助于连续监测与神经退行性疾病（如 AD）相关的功能下降。
