Automated health alerts using in home sensor data for embedded health assessment

WEARABLE SENSORS AND HEALTH MONITORING SYSTEMS
Received 29 October 2014; revised 28 December 2014; accepted 6 March 2015. Date of publication 10 April 2015;
date of current version 22 April 2015.
Digital Object Identifier 10.1109/JTEHM.2015.2421499
Automated Health Alerts Using In-Home Sensor
Data for Embedded Health Assessment
MARJORIE SKUBIC1, (Senior Member, IEEE), RAINER DANE GUEVARA1,2,
AND MARILYN RANTZ3, (Member, IEEE)
1Department of Electrical and Computer Engineering, University of Missouri, Columbia, MO 65211 USA
2Cerner Corporation, Kansas City, MO 64117 USA
3Sinclair School of Nursing, University of Missouri, Columbia, MO 65211 USA
CORRESPONDING AUTHOR: M. SKUBIC (skubicm@missouri.edu)
The work was supported in part by the U.S. National Science Foundation under Grant IIS-0428420 and in part by the
National Institutes of Health under Grant 1R01NR014255 and Grant 1R21NR011197-01.
ABSTRACT We present an example of unobtrusive, continuous monitoring in the home for the purpose
of assessing early health changes. Sensors embedded in the environment capture behavior and activity
patterns. Changes in patterns are detected as potential signs of changing health. We first present results of a
preliminary study investigating 22 features extracted from in-home sensor data. A 1-D alert algorithm was
then implemented to generate health alerts to clinicians in a senior housing facility. Clinicians analyze each
alert and provide a rating on the clinical relevance. These ratings are then used as ground truth for training and
testing classifiers. Here, we present the methodology for four classification approaches that fuse multisensor
data. Results are shown using embedded sensor data and health alert ratings collected on 21 seniors over
nine months. The best results show similar performance for two techniques, where one approach uses only
domain knowledge and the second uses supervised learning for training. Finally, we propose a health change
detection model based on these results and clinical expertise. The system of in-home sensors and algorithms
for automated health alerts provides a method for detecting health problems very early so that early treatment
is possible. This method of passive in-home sensing alleviates compliance issues.
INDEX TERMS Behavioral bio-markers, eldercare monitoring, health alerts, in-home sensing.
I. INTRODUCTION
Our view of embedded health assessment is the on-going
assessment of health changes based on an individual’s
behavior and activity patterns and baseline health conditions.
Sensors embedded in the environment are used to collect
behavior and activity patterns for the purpose of detecting
health changes. Early detection is the key to promoting health,
independence, and function as people age [1], [2]. Identifying
and assessing problems early, while they are still small,
provides a window of opportunity for interventions to
alleviate problems before they become catastrophic. Older
adults will benefit from early detection and recognition of
small changes in health conditions and get help early when
treatment is the most effective. Most importantly, function
can be restored so they can continue living independently.
Recently, there has been an increased focus on technology
for enabling independent living and healthy aging. A major
challenge for studies in this area is the capture of ground truth
data sufficient for training and testing purposes. For example,
students have been enlisted to act out activities of daily
living (ADLs) to create labeled data sets, e.g., for studying
statistical activity recognition methods [3], [4]. Other work
has used smaller datasets from a few volunteers, such as the
statistical predictive algorithm to model circadian activity
rhythms [5], mixture model analysis to infer activities of
one user, validated with a manual log [6], and fuzzy rules
used to classify activities in the home [7]. Although progress
continues, the difficulties associated with collecting longitu-
dinal sensor data along with real health data of subjects have
hindered studies on embedded health assessment.
In this paper, we present an example of unobtrusive,
continuous monitoring in the home for the purpose of
embedded health assessment, to address the management
of chronic conditions as people age. An embedded sensor
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Skubic et al.: Automated Health Alerts Using In-Home Sensor Data for Embedded Health Assessment
network collects data on behavior and activity patterns.
A one-dimensional (1-D) alert algorithm is used to
generate health alerts to clinicians in a senior housing facility.
Clinicians analyze each alert using an electronic health
record (EHR) and an interactive web interface for visualizing
the sensor data. Based on their clinical expertise, they rate
the clinical relevance of the alert. Here, we use the ratings
as ground truth labels for health changes and test
multi-dimensional approaches for classifying alerts as good
or poor.
The approach is tested in a senior housing site called
TigerPlace, which comprises independent living apartments
that support seniors in the same apartment through the end
of life. Nearly all residents have at least one chronic health
condition. Over half have multiple chronic conditions, which
include ailments such as arthritis, heart disease, diabetes, and
hypertension. None of the study participants had significant
cognitive impairments.
In Section II, we include a review of related work.
Section III describes the sensor network used in this study,
an initial investigation of feature space using the in-home
sensors for detecting health decline, and the automated health
alert process used for testing the embedded health assessment
concept. Section IV describes four health alert classification
methods tested; Section V presents the results. The discussion
in Section VI includes advantages and limitations of the
health alert system. Based on the study results, as well as
our clinical experience in using the sensors, we propose a
model for detecting health decline using continuous in-home
monitoring. We conclude in Section VII.
II. RELATED WORK
The variety of related work shows the interest and potential
of embedded health assessment. Both daytime and night time
activity have been investigated using in-home sensors. For
example, passive infrared (PIR) motion sensors have been
used to capture activity in a particular location in the
home [8], [9]. The pattern of room to room activity
has been studied as a means of investigating health
changes [5], [6], [10], [11]. Motion density from PIR motion
sensors (i.e., number of events per unit time) can capture
overall activity level that may be linked to health
condition [12]–[14]. ADLs have been captured by a variety
of sensor types including motion sensors, discrete switches,
powerline monitoring, and computer vision [3], [4],
[15]–[18]. In addition, sleep patterns have been studied using
motion sensors [19], [20], bed mats [21], [22], or load
cells [23], [24]. Other work has focused on the detection of
cognitive changes, using a combination of motion, bed and
door sensing, medication tracking, use of a home computer,
cognitive computer games for monitoring and remediation,
and a phone sensor for detecting incoming and outgoing
calls [8], [25]–[27].
Walking gait in the home is of interest because of the
link to both physical and cognitive health [28]–[32]. Walking
speed has been captured using motion sensors [33], [34],
video [35], [36], radar [37], and depth images [38], [39].
In addition, significant effort using in-home sensing
has focused on safety, e.g., fall detection [40]–[46] and
wandering [47], [48].
One challenge for researchers is collecting enough
in-home sensor data to establish correlations with clinical
assessments, although there is some recent work in this
area [49]–[51]. Much of the recent research is specifically
focused on cognitive decline; there is less work on detect-
ing early health changes for generalized health management.
Also, it is important to identify the best parameters to track
for health change; some parameters may be too late for very
early health change detection. For example, tracking ADLs is
important for determining whether independent living is
possible. However, explicit ADL recognition may be too late
in some cases for early interventions; e.g., changes in night
time activity due to urinary tract infections have been detected
before ADL changes appear [52].
Detecting early health change is further complicated by the
variety of home configurations and health conditions. Many
seniors have multiple chronic health conditions to manage,
and the interaction may present changes in a variety of
ways. In the work presented here, we address this variability
by exploring behavioral bio-markers that generalize across
different chronic health conditions and different home sizes
and room layouts.
There is also work on wearable sensor networks and
sensing incorporated into clothing. Some wearable
systems have been studied extensively or advanced to the
stage of commercialization, e.g., accelerometers for fall
detection [42], [44], [53], counting footsteps [54], worn on
the wrist as actigraphy sensors [55], [56], or assessment in
clinics [57], [58]. These remain a challenge for continuous
monitoring and explicit health change detection of seniors
in naturalistic home settings. Many seniors refuse to wear
them, forget to charge batteries, or are unable to operate
them [59], [60]. Thus, they are not practical for continuous,
long term monitoring. In addition, many wearable
sensors are still at the prototype stage and not yet ready
for long-term use in an unstructured home environment.
Challenges still need to be addressed, such as
unobtrusiveness, miniaturization, and robustness before they
can be adopted widely [61].
III. SENSOR NETWORK
Our team has developed a sensor monitoring system for
embedded health assessment in the home, as illustrated in
Fig. 1. The focus is on detecting very early changes in health
status for older adults who are managing chronic health
conditions. Data from sensors installed in apartments are
logged and stored on a secure server; data are logged by
identifier number only as part of the IRB-approved research
study. A typical installation for a one bedroom apartment as
used in this study is shown in Fig. 2 with 11 motion sensors,
a bed sensor, and a temperature sensor for capturing stove and
oven activity.
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FIGURE 1. Integrated sensor network with health alerts and ratings on
clinical relevance.
FIGURE 2. A typical one bedroom apartment with embedded sensors, as
used in this study.
Passive infrared (PIR) motion sensors are used to capture
motion in a room area and also for localized activity, e.g., in
the refrigerator, in kitchen cabinets, on the ceiling over the
shower, and on the ceiling over the front door to detect apart-
ment exits. The PIR motion sensors, which use the wireless
X-10 protocol for data transmission, generate an event every
seven seconds if there is continuous motion. This is used as
an artifact to capture the general activity level in the home
by computing a motion density as motion events per unit
time. For example, a resident with a sedentary lifestyle may
generate only 50 motion events per hour, whereas a resident
with a very active life style may generate 400 or more motion
events per hour [62].
A pneumatic bed sensor [21] is installed on the bed
mattress and used to capture sleep patterns. The bed sensor
generates events for restlessness in bed (four levels) as well
as low, normal, and high events for pulse rate and respiration
rate. For those residents who often sleep in a recliner chair,
the bed sensor is installed in the chair. Sensor networks with
motion, bed, chair and stove sensing have been deployed in
TigerPlace apartments since 2005. Automated monitoring is
used to detect the absence of sensor data, e.g., in the case of
battery failures. However, there is still some data loss due to
the brittleness of the X10 transmission.
A. INVESTIGATING BEHAVIORAL FEATURE SPACE
FOR CAPTURING HEALTH DECLINE
The in-home sensor data were investigated for use in
detecting health decline through machine learning techniques
coupled with input from the clinical research partners.
Initially, clinicians provided a list of features that might be
important for capturing health changes, related to behavior
activity and sleep patterns. This set was further investigated
using a systematic feature selection process retrospectively
on data collected in senior apartments.
We did a broad investigation of 22 features extracted from
motion and bed sensor data using a forward feature selection
process. Case studies on two elderly residents were used
for this initial investigation, where ground truth labels were
generated manually by looking at the health records and
nurses’ notes. Each day was labeled either as a normal day
(a non-alert day) or an abnormal day (a day that would
warrant a health alert). For this feature investigation, days
with extended visitor activity, more than 12 hours out of the
home, or significant sensor failures were removed from the
datasets. After filtering these days, case study #1 included
267 normal days and 38 alert days; case study #2 included
567 normal days and 32 alert days.
Features extracted from motion sensor data included
activity in the bathroom, bedroom, and living room, time out
of the home, time with visitors, and overall activity level
estimated from motion density [13], [63]. Kitchen activity
was not included due to sensor failures. Also, TigerPlace
residents seldom use their kitchens for preparing food due
to the common dining facility; thus, kitchen features are not
as important for this population. Features extracted from bed
sensor data included time in bed, restlessness in bed, pulse
events, and respiration events. All features were normalized
for this investigation.
The feature selection process used a one class
classification (OCC) method due to the class imbalance.
Several OCC methods were tested, including the Support
Vector Machine (SVM), nearest neighbor (NN-d),
mixture of Gaussians, and Parzen density [63], [64]. The
NN-d method showed more stable results overall; thus,
we present the feature selection results using NN-d.
OCC performance is based on the area under the Receiver
Operating Characteristics (ROC) curve. For the forward
search, each feature is first tested individually and the best
feature is selected. Then, additional feature combinations
are tested, and features are added one at a time until the
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performance stabilizes or declines. The best combination is
considered to be the one that first achieves the best classifi-
cation performance.
Results of the forward search showed a different best
combination for each case study. Table 1 shows the features
tested and the best feature combination selected for each
case [63]. Features common to both best sets include
bathroom time, visitor time, and bed sensor events.
In summary, bathroom visits, sleep patterns, and socialization
activity were shown to be key in recognizing early health
changes for these two residents. These results were used to
inform the approach used for generating health alerts in the
study described below.
TABLE 1. Results of the forward feature selection process.
Retrospective analysis also revealed that the data form
clusters in feature space. Our observation is that normal days
tend to cluster, and abnormal days appear as outliers [63].
Fig. 3 shows the data for case study #2. There are still
challenges in determining valid health alert days. Outliers
may result from real health changes or may be due to ‘‘noise,’’
such as a sensor failure, unusually long visitor activity,
an extended absence, or an isolated abnormal day because,
e.g., someone exercised excessively.
B. GENERATING HEALTH ALERTS
To test the use of in-home sensor data for capturing health
decline, an automated health alert system has been developed
FIGURE 3. Principal components analysis (PCA) reduction of sensor data
collected on case study #2 with features extracted from the motion and
bed sensor data. Each data point represents one day (599 days total;
32 abnormal days).
for prospective use. The logged sensor data are automatically
analyzed on a daily basis, looking for changes in an
individual’s data patterns. If a change is detected for the
current day, an alert email is sent to clinicians [65].
The health alert email includes two web links. One is a link
into the web portal which facilitates fast access to the sensor
data visualization, showing a two week window of data before
the alert and supporting an interactive interface for zooming
out, drilling down, or displaying other parameters. This pro-
vides context to the clinician and helps determine whether the
alert is relevant for this resident from a clinical perspective.
The second link provides access to a feedback web page
that allows the clinician to rate the clinical relevance of the
alert on a five point scale, from 1 (not clinically relevant)
to 5 (very clinically relevant). This rating is then used as
ground truth labels to aid in evaluation and further develop-
ment of the alert algorithms.
On average, the clinician takes about two minutes to
display the sensor data, analyze the alert, determine whether
action is warranted, and provide feedback [66]. For the study
reported here, 4 clinicians provided feedback (one physician
and three nurses), based on their clinical expertise with older
adults [66].
The alert algorithm was developed through retrospective
analysis and collaboration with clinicians. Health events of
senior residents with sensors were examined retrospectively,
looking at emergency room visits, hospitalizations, and falls.
A researcher manually reviewed sensor data leading up to the
health events for signs of changes before the event occurred.
Potential algorithms were then tested iteratively with a group
of clinical researchers until consensus was reached. The
approach looks at the sensor values per day, compared to a
moving baseline of two weeks immediately before the day
examined, i.e., relative sensor values are used rather than
actual counts. Thresholds were set to increase the likelihood
of detecting critical health changes even if it resulted in a high
percentage of false alarms.
The two week moving baseline was chosen on the recom-
mendation of clinicians after retrospective analysis of sensor
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data patterns, as a compromise to capture both sudden and
gradual health changes [66]. Each resident has a personalized
normal that is reflected uniquely in the sensor data patterns,
depending on health condition, usual lifestyle pattern, the size
of the apartment, and the number of sensors. This strategy
of change detection has facilitated the testing of health alerts
even in a diverse group of seniors with varying levels of health
and different chronic ailments.
TABLE 2. Alert parameters and sensor data monitored for the alerts.
Table 2 shows the alert parameters and sensor data
monitored for the health alerts, chosen as a result of the
collaborative analysis. For each parameter, the system
computes a mean and standard deviation for the two week
baseline window. If the current day’s values vary from
the mean beyond a pre-determined number of standard
deviations, an alert is generated. The standard deviation
multiplier varies somewhat for different behaviors
(from 2.5 to 4), according to the clinical research team’s
view of the relative importance of the parameters. Relative
changes are computed for three time periods: (1) a 24-hour
day, midnight to midnight, (2) daytime, 8am to 8pm, and
(3) nighttime, midnight to 6am. The email alerts generated
include the parameter that caused the alert, the time period
of the change, the direction of change (increase or decrease),
and the number of standard deviations from mean (how big
is the change).
Although both increasing and decreasing changes of all
parameters are used to flag alerts, the clinical research team
recognized that not all such changes would denote a health
decline. For example, increasing living room activity during
the day is not typically a cause for concern, while increasing
living room activity during the night can indicate a change
in health status. In contrast, any change in bathroom activity
might indicate a health problem. For completeness in testing,
all of these changing conditions are used for generating auto-
mated health alerts.
With this 1-D strategy, about half of the alerts generated
are false alarms. Through manual investigation, it appears
we are capturing nearly all of the obvious health changes.
We tracked changes in health status (emergency room
visits, hospitalizations, and falls) and compared with alerts to
investigate potential false negatives. Only ten false negative
events were detected during a one year period, across
21 senior participants. However, other potential alerts might
be missed. Nonetheless, capturing a clinical rating on the
health alerts has allowed us to create a unique dataset for
investigating more advanced algorithms for health alerts
beyond this simple 1-D approach.
IV. METHODS AND PROCEDURES
In this section, we describe the classifiers investigated for
determining whether a particular day’s sensor data should
be classified as an alert day or not. The health alert
ratings provided by the clinicians are used as ground
truth labels in training and testing. Four classifiers were
studied. The first is a fuzzy pattern tree (FPT) that does not
require training but rather takes advantage of domain knowl-
edge from our clinical partners. The remaining classifier
methods rely on labeled training data and include the fuzzy
K-nearest neighbor (FKNN), the neural network (NN), and
the support vector machine (SVM). These classifiers were
chosen for the study to provide a comparison between
the use of domain knowledge only vs. trained classifiers
that support a nonlinear decision boundary. The nonlinear
decision boundary was deemed essential to match our obser-
vations about the normal vs. abnormal days as illustrated
in Fig. 3.
A. FEATURE SPACE
In analyzing the health alerts generated for the parameters
listed in Table 2, it was observed that some of the parameters
do not typically cause alerts and others generate a few alerts
but not enough to be used for supervised learning. Thus,
for the study described here, we looked at the following
four alert parameters: bathroom activity, bed restlessness,
kitchen activity, and living room activity. If both increasing
and decreasing changes (the current day’s count compared
to the baseline period) are considered for all three time
periods (daytime, night time, and full day), the dimension-
ality of the feature space is 24. We also investigated a
12-dimensional (12-D) feature space, considering only
increases in each parameter. Fig. 4 shows a principal compo-
nents analysis (PCA) reduction of the 24-dimensional (24-D)
and 12-D feature spaces, where each blue × indicates a good
alert day and each red o indicates a bad alert day (normal day);
as shown, there is not good separation between the good alert
and bad alert classes.
After further analysis of the alert ratings and discussion
with our clinical partners, the feature space was reduced
to consider the following six features: increasing nighttime
activity in the living room, kitchen, and bathroom, increas-
ing full day activity in the bathroom, and increasing bed
restlessness at both nighttime and during the full day.
A PCA reduction of this 6-dimensional (6-D) feature space
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FIGURE 4. PCA reduction of 24-D feature vectors (top) and 12-D feature
vectors (bottom) from the early illness alert study. Red O’are poor alert
days; blue X’s are good alert days as rated by clinicians.
FIGURE 5. PCA reduction of 6-D feature vectors from the early illness
alert study. Red O’s are poor alert days; blue X’s are good alert days as
rated by clinicians.
is shown in Fig. 5. Normal days (i.e., poor alert days) tend
to cluster, and the abnormal days (good alert days) tend to
be outliers around the cluster center, although ‘‘noise’’ is
still a factor. Here, we report the methods and results using
6-D feature space and compare to the 12-D feature space.
All features are normalized before input to the
classifiers.
B. FUZZY PATTERN TREE
A fuzzy pattern tree (FPT) [67] was investigated as a method
that uses domain knowledge and does not require train-
ing. The six features described above were combined in a
FPT using an OR operator, providing a ‘‘rule’’ that is easy
for clinicians to interpret [65]. Intuitively, the output is as
follows:
IF Bathroom activity for the full day is an Increase
OR Bathroom activity at night time is an Increase
OR Bed restlessness for the full day is an Increase
OR Bed restlessness at night time is an Increase
OR Kitchen activity at night time is an Increase
OR Living room activity at night time is an Increase
THEN Alert is Clinically Relevant
Gaussian-based membership functions were used for the
input parameters. The Yager t-conorm [68] was chosen as
the OR operator to explore the additive combination of
parameters as opposed to the standard maximum. That is,
if small changes were observed in several parameters, these
resulted in a cumulative effect in determining whether an alert
was warranted. The Yager parameter w sets the degree of
optimism (how much greater the output is over the standard
maximum operator) when two inputs are OR-ed together.
For the work presented here, w = 3 generated the best
classification empirically. For comparison, a 12-D FPT was
also tested.
C. FUZZY K-NEAREST NEIGHBOR
A FKNN classifier was trained and tested with
both 6-D and 12-D feature vectors (using Matlab functions).
The standard Euclidean distance is used as a dissimilarity
measure. For the crisp K-Nearest Neighbor (KNN) method,
the classifier finds the K neighbors in the training set that are
closest to the test vector. K is chosen as an odd-numbered
value; the majority class of the K neighbors determines the
class of the test vector. In contrast to the crisp KNN method,
the FKNN produces a membership value in [0,1] that assigns
partial membership in each class to the test vector. The class
with the highest membership value is used here to determine
the class of the test vector.
The method was tested using 10-fold cross validation with
90% of the data used for training and 10% used for testing
in each fold; the cumulative results are reported. Each set of
FKNN experiments varied K using 1, 3, 5, 7, 9, and 11. The
best results are reported here, with K = 11.
D. NEURAL NETWORK
Two sets of 10-fold cross validation experiments were
performed to test 6-D and 12-D NN classifiers
(using Matlab functions). Both sets of NNs used 5 hidden
nodes and one output node and the sigmoid activation
function at each node. After each training sample, the NNs
were updated using scaled gradient back propagation. Each
fold randomly split the dataset into 70% training data,
15% validation data, and 15% testing data. The training
data was used to update the NNs and after each epoch,
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a sum of squared error (SSE) function was computed
using the validation data. Training was terminated when the
SSE increased for several epochs. Cumulative results on the
cross-validation experiments are reported.
E. SUPPORT VECTOR MACHINE
The support vector machine (SVM) was also tested to inves-
tigate a supervised learning approach [65]. We investigated
both a linear and radial basis function (RBF) kernel (using
Matlab functions) and tested both the 6-D and 12-D features
as described above. The RBF kernel performed better than
the linear kernel; the RBF results are reported here. Again,
10-fold cross validation is used for the experiments, and the
cumulative results are reported.
V. RESULTS
The four classifiers were tested with a set of health alert
ratings spanning nine months on 21 senior residents. Table 3
shows the number of alerts used for each alert parameter that
were rated as either good alerts or poor alerts. Good alerts
included the alerts that were rated as a 4 or 5 (clinically
relevant or very clinically relevant). The poor alerts included
those rated as a 1 or 2 (not clinically relevant or less clinically
relevant). The alerts rated as a 3 were interpreted as being
neutral and were not included in this test.
TABLE 3. Health alerts used for testing (1-D).
TABLE 4. Classification results (in percentages).
Table 4 shows the results of the four classification methods
for both the 6-D and 12-D feature sets. The best
classifications are achieved with the 6-D FPT and SVM
and the 12-D FKNN. For comparison, we have included the
ROC curves for the 6-D FPT and SVM classifiers, shown
in Fig. 6. Although the accuracy rate is slightly higher for
the FPT, the ROC curves show their classification perfor-
mance is very similar. As shown in Table 3, the percentage of
FIGURE 6. ROC curves for the SVM and fuzzy pattern tree (FPT) using
6-D feature vectors.
good alerts using the 1-D alert algorithm was 39%. Thus, the
multi-dimensional classifiers performed significantly better.
VI. DISCUSSION
A preliminary feature selection investigation examined
22 features from in-home motion and bed sensors. This initial
retrospective study showed the importance of bathroom
activity, sleep patterns, and socialization behavior in detect-
ing health change for the two subjects. A 1-D health alert
algorithm was then developed for testing in a prospec-
tive study with 21 seniors; feedback on clinical relevance
was provided by clinicians. Using data from this larger
prospective study, we showed that multi-dimensional classi-
fiers performed significantly better than the 1-D algorithm,
with the best 6-D performance at 86% compared to 39%
at 1-D. The results also show that a 6-D classifier based only
on domain knowledge performed slightly better than the best
6-D classifier using supervised machine learning.
One motivation for this study was to test the embedded
health assessment concept in a home setting. The results show
that continuous monitoring with in-home sensors can be used
effectively to detect health changes. Note, however, that no
diagnoses are made; there is only detection of a potential
health problem. The system functions as a clinical decision
support system with the clinician determining whether an
intervention is warranted.
A second motivation was to identify appropriate sensor-
derived features for detecting health decline. Both the feature
selection study and the prospective health alert study illus-
trate the importance of tracking bathroom activity and bed
parameters. The labeled data in Table 3 shows a much higher
percentage of clinically relevant alerts for these activities
compared to kitchen and living room activity.
The best features found here are reflective of the study
participants and their health conditions. The best dis-
criminating features might be different for a group of
cognitively impaired individuals. It is also likely that other
features will be important in different housing contexts.
For example, we would expect kitchen activity to play a
stronger role where seniors are responsible for preparing their
own meals.
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The TigerPlace clinical staff liked the health alerts and
wanted to continue them in spite of the high false alarm
rate. At the end of the prospective study, hyperlinks were
added to the alerts to allow clinical staff to open new progress
and visit notes in the EHR directly from the alert emails.
Thus, their clinical workflow was improved at the
same time.
A. NEW SENSORS NEEDED
The results of the studies showed the importance of bed
sensor data for capturing early signs of health decline.
However, the clinical team felt that quantitative data on pulse
and respiration were necessary to fully use these parameters.
This led to the development of an improved bed sensor that
estimates quantitative pulse and respiration rates in addition
to reporting restlessness in bed. The improved sensor uses
hydraulic transducers (flexible tubes of water) placed under
the mattress [22] which has proven to be less invasive and
more comfortable than the original pneumatic transducers
placed on top of the mattress. Quantitative estimates of
pulse rate, respiration rate, and restlessness are stored every
15 seconds. The new sensor also provides a clean reading of
on/off bed transitions without the noise of the previous sensor.
Thus, this captures a rich set of data on physiological state as
well as sleep patterns.
The clinical research team also noted the importance
of logging walking speed and gait patterns as a means of
tracking health and fall risk. Changes in gait patterns
have been linked to both physical and cognitive
decline [28]–[32] and are particularly important for detecting
very early signs of health decline. As a result, our team
investigated the capture of in-home gait parameters with
Doppler radar [37], dual webcams [36], and depth imagery
from the Microsoft Kinect [38]. While walking speed and
stride information can be captured with all three sensing
modalities, the Kinect has proven to be the most robust and
easiest to use. A gait model of walking speed, stride time,
stride length, and height is learned for each resident [39].
The segmented resident walks appear as a cluster with
visitors as outliers. Thus, visitor walks can be excluded from
the model. Algorithms have also been developed for fall
detection using Kinect depth images [46].
B. MODELING HEALTH DECLINE WITH BEHAVIORAL
BIO-MARKERS
The results of the studies show that some changes
indicate health decline and some do not. After reviewing
the results and considering their clinical experience in using
sensor-based health alerts for longitudinal studies, our clini-
cal research team revisited the question of which parameters
are important for detecting early signs of health decline.
Six clinicians contributed to the discussion: three nurses,
two social workers, and one physician. Table 5 shows the
changes considered and ultimately chosen for health alerts.
This represents our proposed model for detecting health
decline with in-home sensors.
TABLE 5. Model for detecting health decline with in-home sensors.
One principle guiding this model is that daytime increases
in normal daytime activity should not generate an alert.
Likewise, night time increases in normal night time activity
should not generate an alert. However, night time increases in
normal daytime activity is a concern. Some changes are left
out completely, e.g., bedroom activity and visitor activity. The
clinical staff report that these changes have too many incon-
sistencies across different seniors to be reliable behavioral
bio-markers. We have included changes in time away from
home as part of the model. However, the clinical researchers
were not all in agreement, noting that it is important to capture
the reason seniors leave home. For example, excursions due
to social engagements are viewed as a sign of good health,
whereas increased time away from home due to medical
appointments is likely to indicate a health problem. The social
workers also noted that changes in bed sensor data are likely
to appear sooner than changes in time away from home.
Other sensor changes in the model are included because
of our experience in both retrospective and prospective
research studies such as the studies described in this paper
(e.g., bed restlessness) or because of research documenting
signs of health decline, e.g., gait changes [28]–[32].
The investigation of in-home sensors for early detection
of health changes has been aided by an interdisciplinary
team and the use of TigerPlace as a research site. From the
beginning, TigerPlace was designed to be a living laboratory
affiliated with the University of Missouri, Sinclair School
of Nursing (SSON) [69]. The housing facility was built and
is operated by Americare; however, the clinical operation
is run by the SSON. About 65 senior residents reside
in 54 independent apartments. An electronic health record
was developed by our research team for the purpose of
tracking changes in residents’ health status [70]. Thus,
it provides a unique opportunity to conduct longitudinal
studies on embedded health assessment.
We began installing sensors in TigerPlace apartments
in October, 2005 and initially studied a small number of
2700111 VOLUME 3, 2015

residents as case studies. We now operate 20-25 active
sensor networks continuously for IRB-approved longitudinal
research studies. The sensor data for the study described here
was collected as part of a year-long intervention study in
which 21 seniors had in-home sensors (PIR motion sensors
and pneumatic bed sensors) with 1-D health alerts
and 20 seniors were control subjects receiving normal
care [66], [71]. With the health alert system, clinicians were
able to detect early signs of urinary tract infections and
other acute infections such as pneumonia, upper respiratory
infections, heart failure, post-hospitalization pain, delirium,
and hypoglycemia [66]. At the end of the study the interven-
tion group showed significantly better health outcomes than
the control group [66], [70], [71].
A randomized control study is currently underway in other
senior housing with 70 seniors as controls and 70 seniors
with sensors and health alerts. This current study uses the
new hydraulic bed sensor and the Kinect-based in-home
gait analysis system. A commercialization effort is also
underway with a goal of keeping the system cost effective.
The equipment of PIR motion sensors, bed sensor, and depth
camera gait system is relatively inexpensive (about $2000).
The bigger cost will be managing the deployment and
providing trained clinicians for receiving and interpreting
the health alerts. However, even if the annual costs are
$4000-$5000, the system can be very cost effective due to
the early treatment of health problems when costs are less.
Avoiding hospitalizations or re-admissions, as has occurred
with TigerPlace residents, can offer a substantial overall cost
savings. We anticipate that the health alert system will also
allow seniors more flexibility in housing choices, including
the ability to stay in an existing private home. This too would
offer cost savings and provide an improved quality of life for
seniors as they age.
VII. CONCLUSION
In this paper, we present studies designed to investigate
embedded health assessment. A forward search was first used
to retrospectively investigate the feature space of embedded
in-home sensors. We also described a prospective study using
1-D health alerts. Clinical ratings on the health alerts were
provided by clinicians and used to train and test multi-D
classifiers. The best 6-D performance was achieved by a
FPT based on domain knowledge only, although the SVM
(trained on labeled training data) had a similar performance.
To improve the current performance, we will investigate
on-line learning using the alert ratings as feedback. The work
presented here shows that domain knowledge could be used
for initial classification to build up enough data to support
on-line learning methods.
Finally, based on the study results and our experience
using health alerts prospectively, we proposed a model for
detecting health decline with in-home sensors. A randomized
control study using this model with the hydraulic bed sensor,
motion sensors, and in-home gait is underway to further
test the potential of embedded health assessment. A system
that recognizes very early signs of health decline passively,
without requiring the user to wear anything, charge batteries,
or do anything special, has enormous implications for
seniors’ health trajectories. Identifying health decline early
provides a window of opportunity for early treatment and
intervention that can address health problems before they
become catastrophic. This offers the potential for improved
health outcomes, reduced healthcare costs, continued inde-
pendence, and better quality of life.
ACKNOWLEDGMENT
The authors would like to thank the Eldertech team at the
University of Missouri for their help and support with this
work.
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MARJORIE SKUBIC (S’90–M’91–SM’13)
received the Ph.D. degree in computer science
from Texas A&M University, College Station,
TX, USA, in 1997. She specialized in distributed
telerobotics and robot programming by demon-
stration with Texas A&M University. In addition
to her academic experience, she has spent
14 years working in industry in real-time
applications, such as data acquisition and
automation. She established the Center for
Eldercare and Rehabilitation Technology, University of Missouri, in 2006,
where she serves as the Center Director of an interdisciplinary team. The
center supports proactive models of health care, such as monitoring systems
that noninvasively track the physical and cognitive health of elderly residents
in their homes and generate alerts that flag health changes. The center’s
recent work also includes the investigation of automated screening of athletes
and pianists to flag injury risks, with the support of preventative exercises to
reduce the risk. She is currently a Professor with the Electrical and Computer
Engineering Department, University of Missouri, with a joint appointment
in Computer Science. Her current research interests include human–robot
interaction, spatial referencing interfaces, computational intelligence, sensor
networks for eldercare, and preventative screening tools.
RAINER DANE GUEVARA received the
M.S. degree in computer engineering from the
University of Missouri, Columbia, MO, USA,
in 2012. His thesis focused on using in-home
sensor data for early illness detection of seniors.
He is currently a Software Engineer with Cerner
Corporation, Kansas City, MO. His interests
include computational intelligence, pattern recog-
nition, eldercare technology, and wireless sensor
networks.
MARILYN RANTZ (M’12) received the
Ph.D. degree in nursing from the Univer-
sity of Wisconsin, Milwaukee, USA, in 1992.
She specialized in long-term care health policy
and public program evaluation and gerontological
nursing with the University of Wisconsin.
She was elected into the Institute of Medicine
and also became the only individual to be twice
named as an American Academy of Nursing Edge
Runner for two different innovations in 2012.
She is currently a Curators’ Professor with the Sinclair School of Nursing,
University of Missouri, Columbia, where she holds the position of University
Hospital Professor of Nursing, and has an appointment as a Professor with
the Department of Family and Community Medicine, University of Missouri
School of Medicine.
Dr. Rantz has developed and sustained a research program to improve
the quality of care of the elderly. Her innovative work on nursing home
quality spans nearly 30 years, in practice and as a leading Researcher,
and establishes her as a Premier International Expert in quality measure-
ment in nursing homes. In 2012, she secured a U.S.$14.8 million grant
from the Centers for Medicare and Medicaid Services for their initia-
tive to reduce avoidable hospitalizations among nursing facility residents.
In total, she and her multidisciplinary research teams have garnered over
U.S.$60 million in funds to support their work measuring effectiveness of
nurse care coordination, conduct cutting edge research in long-term care, new
delivery models of care for older adults, and most recently, for technology
development to enhance aging in place of community-dwelling elders.
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