Author: Chang, W.-Y.,Chang, K.-W,Yeh-Liang Hsu(2015-06-06);
recommendation: Yeh-Liang Hsu (2015-06-06).
Using fractal dimension derived from trajectory measured by motion sensing carpet to assess wandering behaviors of dementia patients
1. Background and purpose of the research
Wandering is a prevalent behavior in dementia patients. Warren (1999) compared the frequency of wandering. Of
the 638 community-residing dementia patients examined, wandering behavior
occurred in 17.4% of participants. It was significantly more prevalent in
patients with Alzheimer dementia than those with vascular dementia or other dementia.
Martino-Saltzman et al. (1991), characterize ambulation in older people with
dementia according to its geographical pattern as direct, lapping, pacing, or
random. Travel efficiency (percentage of direct travel) was significantly
related to cognitive status (r =0.56),
with inefficient travel most prevalent in severely demented participants.
In recent years, a variety of assistive technologies
based on “ambient-assisted living” (AAL) tools are developed to assess the
wandering behavior. Kim et al. (2009) tried to distinguish wandering patterns
from normal patterns in a nursing home by using triaxial
accelerometer sensors. Campo et al. (2010) developed methods for determining
normal trajectory classes and triggering alarms when the trajectories are
unusual by using infrared sensors. Vuong et al. (2014)
automatically classify wandering patterns of dementia patients with active RFID
system based on the Martino–Saltzman typology into direct, random, pacing, and
lapping patterns. Kearns (2010) used “fractal dimension” (Fractal D), a measure
of movement path tortuosity (directed vs. irregular or apparently aimless
locomotion) to access wandering behaviors of dementia patients. Ultra-wideband
sensors were used to measure day time locomotion to an accuracy of 20 cm in 14
elderly residents in an assisted living facility. Fractal D was found to be significantly
and negatively correlated with cognitive status as measured by the Mini Mental
State Examination (MMSE) administered to each participant at the study’s end.
The purpose of the research is to use fractal dimension
derived from trajectory measured by motion sensing carpet to assess wandering
behaviors of dementia patients. In the initial study, this system has been
implemented in the rooms of 4 demented older adults to collect data.
WhizCarpet is composed of 50cm×50cm “puzzle floor mat” modular motion sensing
units, which can be assembled freely into any size and shape according to the
setup of the home environment (Chang et. al, 2014). WhizCarpet system was implemented in the rooms of 4 demented older
adults in a nursing home in Tainan (Figure 1, left). Four residents (A,
B, C, D) are 82, 66, 85, 85 years old, respectively. All four participants are diagnosed
with dementia. Two of them are wanderers (A, B), and the other two are non-wanderers
(C, D). The locomotion data was collected by a
microprocessor and transmitted to the cloud server, and can be display on an
App graphically in real time (Figure 1, right).
Figure 1. WhizCarpet implemented
in the nursing home
Wandering events were identified and stored in the cloud
server. Fractal D was calculated for each event. Figure 2 shows the duration,
travel rate and fractal D of four typical wandering events: direct (Figure
2(a)), pacing/lapping (Figure 2(b)), random (Figure 2(c)).
Figure 2. The duration, travel rate and fractal D of four typical
3. Results and future work
Figure 3 compares the wandering events collected on a
day between participant A (wanderer) and C
(non-wanderer). The mean of Fractal Ds of the 27 wandering events of
participant A is 1.298 (SD=0.25); while the mean of Fractal Ds of the 43 wandering
events of participant C is 1.149 (SD=0.17). With the promising initial results,
we are tuning the algorithm and collecting long-term data of the 4 residents.
events collected on a day of participant A (wanderer)
and C (non-wanderer)
Warren, A., Rosenblatt, A.,
& Lyketsos, C. G. (1999). Wandering behaviour in community-residing persons with dementia. Int.
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Martino-Saltzman, D., Blasch, B. B., Morris, R. D., & McNeal, L. W. (1991).
Travel behavior of nursing home residents perceived as wanderers and non-wanderers.
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Kim, K. J., Hassan, M. M., Na,
S. H., & Huh, E. N. (2009, December). Dementia wandering detection and
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Kearns, W. D., Nams, V. O., & Fozard, J. L.
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