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AuthorsChe-Chang Yang (2010-09-22); recommended: Yeh-Liang Hsu (2010-02-21)
Note: This article is the Chapter 1 of Che-Chang Yang’s doctoral thesis “Development of a Home Telehealth System for Telemonitoring Physical Activity and Mobility of the Elderly”.

Chapter 1. Introduction

1.1 Research background

1.1.1 Functional ability, mobility and ageing

The world’s elder population is rapidly growing. The World Health Organization (WHO) predicts the global population proportion over 60 to reach 22% in 2050 [WHO Global Health Observatory, 2009]. Taiwan has also become an ageing society. The population proportion aged 65 and over in Taiwan accounted for 7% in 1993, and this figure reached 10.6% in 2009 [Ministry of Interior, Taiwan, 2010]. With the continuing growth of elderly population and a decline in birth rate, it is important to help people remain independent and active. Maintaining autonomy and independence of the elderly is the key goal in the “Active Ageing” policy led by the WHO. The “International Plan of Action on Ageing” prompted by the United Nations (UN) has also adapted independence as one of “United Nations Principles for Older Persons” to encourage governments to incorporate the principles into their national programs or policies [United Nations, 2002].

The ageing process of the elderly results in declined functional status and decreased mobility, which affects their level of self-care and independence. Functional status can be defined as the ability to perform activities necessary to ensure well-being, and it can be assessed by examining the ability to carry out various activities of daily living (ADLs). [Heikkinen, 1998]. Limitations in basic ADLs and instrumental ADLs (IADLs) are strongly associated with less mobility [Shimada et al., 2010]. Katz et al. indentified 6 basic ADL items associated with one’s living independence: bathing, dressing, toileting, transfer, continence and feeding. The IADLs further describe the ability of performing more complex ADLs in telephone use, shopping, food preparation, housekeeping, laundry, transportation, handling medication and finances. The Katz ADL Scales and IADL Scales have both been developed over the past decades to assess independence [Katz et al., 1970; 1976; Lawton et al., 1969]. Currently the Barthel Index (BI) and its modified version (MBI) have been widely accepted as the basis of ADL/IADL assessment tool to evaluate the independence of elderly adults.

Mobility is a crucial aspect regarding one’s living independence. It is sensitive to changes in health and psychological status and is one of the most crucial factors determining one’s functional capacity [Celler et al., 1994; Heikkinen, 1998]. Physical activity is regarded as any bodily movement produced by skeletal muscles and results in energy expenditure [Caspersen et al., 1985]. Limited physical activity (PA) and mobility are associated with a deterioration of health and functional impairment in the elderly people [Folden et al., 1990]. Impaired mobility due to age-related loss of muscle strength also increases the risk of falls [Buchner, 1997]. Among the 10 activity assessment items(feeding, bathing, grooming, dressing, bowels, bladder, toilet use, transfers, mobility, and stairs) in the Barthel Index, “transfers” and “mobility” score higher (15% each) than other 8 items. The Modified Barthel Index also adopts the two items “ambulation” and “bed/chair transfer” to assess mobility. The Elderly Mobility Scale (EMS) has been developed to assess the functional performances in locomotion, balance, gait and postural transitions, in which balance and gait are the two most significant factors for mobility and fall risk [Smith, 1994; Daley et al., 2000]. Mobility can also be related to the performance of PA which focuses primarily on its activity intensity (or energy expenditure, EE). The Physical Activity Scale for the Elderly (PASE) was also developed to assess the duration and intensity due to physical activity [Washburn et al., 1993].

1.1.2 Applicability of monitoring functional status and mobility using home telehealth systems

Although several assessment methods have been developed and validated for assessing the functional status and mobility of elderly people, technologies are expected to facilitate and provide cost-effective and practical assessment alternatives. Researchers have attempted to develop remote monitoring approach to health status of the elderly at home. Celler et al. [1994, 1995] tried to identify changes of health status from simple activity measures automatically and continuously collected by a number of sensors. A telemedicine platform was also used to enable effective data transmission and collection, as well as to prompt timely response and intervention. Such a concept and trial initiated the possibility of monitoring mobility and functional status of the elderly people at home with the use of available technologies.

(1)  Sensor-based approaches to monitoring functional status and mobility

With rapid advances in sensors and telecommunication technologies, human activities can be monitored by means of sensors. The rationale and advantages of utilizing such sensor-based approaches are:

Quantitative and objective: The activities are recorded by sensors. The functional status can be assessed objectively according to the quantitative data, avoiding varied and inconsistent assessment results due to subjective evaluation methods, such as questionnaires and self-reports.

Continuous, long-term monitoring: For the elderly living in their home environment, the transition from functionally healthy to functionally ill might not be easily perceived by themselves or be observed by periodical care interventions. Sensor-based monitoring approaches can provide continuous monitoring to assess functional status on a long-term basis.

Unobtrusiveness: The subjects are not aware of the monitoring facilities in use and hence the systems do not interfere or even change their daily activities and life styles. This minimizes the so-called “white coat effect” possibly brought by traditional assessment methods.

Celler et al. [1994] proposed the concept of implementing sensor networks in a home environment to monitor functional status of the elderly living alone. For measuring ADLs, passive infrared sensors (PIRs) and switches are commonly used to detect the occupancy of human in space (home) and location transfer. Electricity sensors can be used to detect the use of home appliances [Franco et al., 2008]. Motion sensors can also be used to measure human activities. Currently accelerometry has been widely used in the study of physical activity and mobility due to advances in sensor technology (MEMS accelerometers). Accelerometry is preferred because acceleration is proportional to external force and hence can reflect the intensity and frequency of human movement. Accelerometry data can be used to derive information of velocity and displacement data by integration accelerometry data with respect to time. Therefore, accelerometry is capable of providing sufficient information for measuring physical activity and a range of human activities. Accelerometers have been widely accepted as useful and practical sensors for wearable devices to measure and assess physical activity in either clinical/laboratory settings or a free-living environment. Several accelerometry-based applications have also been identified [Mathie et al., 2004].

(2)  Integrating with home telehealth systems

Telehealth is a broader concept than telemedicine. In the U. S. governmental report, telehealth is defined as “the use of electronic information and telecommunications technologies to support long-distance clinical health care, patient and professional health-related education, public health and health administration.” [U. S. Department of Health and Human Services, 2001] Telehealth is a practical approach that connects individuals and healthcare providers through telecommunication technology in a variety of application modalities in locations other than hospitals or clinics [Mann, 2005].

The “United Nations Principles for Older Persons” has addressed that elderly people should be able to reside at home as long as possible, and consequently home has become the centerpiece of healthcare delivery system today. Telehomecare, or the more modern term “home telehealth”, is a relatively recent innovation. According to the Canadian governmental report, telehomecare is defined as “the use of information and communication technologies to enable effective delivery and management of health services at a patient’s residence” [Office of Health and Information Highway, 1998]. Home telehealth refers to the use, by a home care provider, of modern telecommunication and information technology to link patients to single or multiple out-of-home sources of care information, education, or service over short or long distances [Koch, 2006]. Home telehealth differs from telemedicine in the sense that people who transmit and receive medical information are not necessarily medical doctors but the patients themselves and their families, nurses, care-givers, home-helpers and medical technical experts, etc [Tsuji, 2002]. A study suggested that home telehealth services may enhance the users’ timely accessibility to necessary healthcare, reduce preventable hospitalization and decrease direct and indirect medical costs over time [Jia, et al., 2009].

Researchers are working on activity telemonitoring solutions for the elderly living at home. Objective and quantitative data obtained by sensor-based monitoring techniques can be used to assess functional health as well as to evaluate the levels of necessary medical treatments or care services. Scanaill et al. [2006] reviewed several mobility telemonitoring approaches, i.e., the “health smart homes” and wearable systems of different technological complexity that connect home telehealth systems.

The Gerontechnology Research Center (GRC, http://grc.yzu.edu.tw) of Yuan Ze University has also been developing a range of home telehealth-based applications. The concept of “Decentralized Home Telehealth System (DHTS)” has been proposed, and what sets this system innovative from most others is its focus on a highly decentralized monitoring modality and the portable nature of the system [Hsu et al., 2007]. Figure 1 illustrates the information structure of the DHTS. The distributed data server (DDS) is the core unit of DHTS and it has four main functions: receiving data from remote sensors and devices, data logging (MMC stick), data processing and Internet communication. The Internet accessibility of the DDS offers the integratibility to telehealth application and Internet-enabled capabilities. For data request, the DDS can be directly accessed from remote authorized clients using the Internet browsers (e.g., the IE), Visual Basic (VB) or JAVA-supported application programs. This proposed system also provides timely alert reports that respond to emergent events, such as falls or irregular activities. A centralized database can be optionally connected to DHTS if additional applications are required.

Figure 1. The structure of the DHTS

Figure 2 shows the DHTS application fields developed by GRC. Based on the DHTS architecture, five application fields, including environmental monitoring [Cheng et al., 2006], vital sign healthcare, sleep quality monitoring and evaluation [Cheng et al., 2008], telepresence interaction and healthcare robotics [Tsai et al., 2007], and mobility monitoring [Yang et al., 2009] have been developed.

Figure 2. The applications of the decentralized home telehealth system developed by GRC

1.2 Purpose of this research

Although several home activity monitoring techniques and field tests have been presented, further research is still needed to develop a monitoring system integrating accelerometry-based wearable motion detectors and home ADL sensors for the use of monitoring and assessing functional status and mobility of the elderly living at home. Therefore, it is expected that elderly people living alone in their residences may benefit from a home telehealth system that offers simple, low cost, and effective functional status and mobility monitoring and assessment.

The purpose of this research is to develop an activity monitoring system for mobility and functional ability telemonitoring for elderly people living at home. This system is integrated with the DHTS for home use. Figure 3 illustrates the framework of the proposed system. The wearable motion detector (WMD) and home ADL sensors are used to monitor daily activities of the elderly at home. The WMD is a waist-mounted device that uses a tri-axial accelerometer to measure accelerations and tilt angles with respect to the three orthogonal directions (vertical, antero-posterior, medio-lateral). The home ADL sensors are distributed in several locations of interests in a home environment. Passive infrared (PIR) sensors and CT (current transformer) are used to detect home ADLs of the elderly. The activities collected from both the WMD and the home ADL sensors are transmitted to the distributed data server (DDS) via wireless sensor network (WSN) technology.

Figure 3. The system diagram of the proposed monitoring system

Figure 4 further describes the functional framework of the proposed system. Signal processing algorithms are implemented in the WMD to enable real-time activity classification, EE estimation, gait recognition and fall detection. Those identification measures are transmitted to the home DDS. This system also incorporates ADL events that are collected by the home ADL sensors. External application applet or application program containing data analysis scheme can be applied to the data stored in the database and hence facilitates the quantitative assessment of mobility and functional status.

Figure 4. The functional framework of the proposed system

This dissertation is organized as follows. Chapter 2 reviews the accelerometry for physical activity monitoring. Chapter 3 describes the instrument design of the wearable motion detector and the distributed data server. The uses of the wearable motion detector for mobility telemonitoring, including real-time activity classification, EE estimation, gait recognition, and fall detection are presented in Chapter 4 to 6. The design and use of home ADL sensors for ADL telemonitoring is further presented in Chapter 7, while Chapter 8 discusses the mobility assessment and concludes this research.


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