<?xml version="1.0" encoding="UTF-8"?><!DOCTYPE article  PUBLIC "-//NLM//DTD Journal Publishing DTD v3.0 20080202//EN" "http://dtd.nlm.nih.gov/publishing/3.0/journalpublishing3.dtd"><article xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink" dtd-version="3.0" xml:lang="en" article-type="research article"><front><journal-meta><journal-id journal-id-type="publisher-id">APD</journal-id><journal-title-group><journal-title>Advances in Parkinson's Disease</journal-title></journal-title-group><issn pub-type="epub">2169-9712</issn><publisher><publisher-name>Scientific Research Publishing</publisher-name></publisher></journal-meta><article-meta><article-id pub-id-type="doi">10.4236/apd.2021.102002</article-id><article-id pub-id-type="publisher-id">APD-114042</article-id><article-categories><subj-group subj-group-type="heading"><subject>Articles</subject></subj-group><subj-group subj-group-type="Discipline-v2"><subject>Biomedical&amp;Life Sciences</subject><subject> Medicine&amp;Healthcare</subject></subj-group></article-categories><title-group><article-title>
 
 
  Can We Use Consumer-Wearable Activity Tracker Fitbit in Parkinson Disease?
 
</article-title></title-group><contrib-group><contrib contrib-type="author" xlink:type="simple"><name name-style="western"><surname>Kazuo</surname><given-names>Abe</given-names></name><xref ref-type="aff" rid="aff1"><sub>1</sub></xref><xref ref-type="corresp" rid="cor1"><sup>*</sup></xref></contrib></contrib-group><aff id="aff1"><label>1</label><addr-line>Department of Neurology, Hyogo College of Medicine Hospital, Nishinomiya, Japan</addr-line></aff><pub-date pub-type="epub"><day>31</day><month>05</month><year>2021</year></pub-date><volume>10</volume><issue>02</issue><fpage>15</fpage><lpage>23</lpage><history><date date-type="received"><day>1,</day>	<month>April</month>	<year>2021</year></date><date date-type="rev-recd"><day>28,</day>	<month>May</month>	<year>2021</year>	</date><date date-type="accepted"><day>31,</day>	<month>May</month>	<year>2021</year></date></history><permissions><copyright-statement>&#169; Copyright  2014 by authors and Scientific Research Publishing Inc. </copyright-statement><copyright-year>2014</copyright-year><license><license-p>This work is licensed under the Creative Commons Attribution International License (CC BY). http://creativecommons.org/licenses/by/4.0/</license-p></license></permissions><abstract><p>
 
 
  Consumer-wearable activity trackers have been used for monitoring health-related metrics to estimate steps, distance, physical activity, energy expenditure, and sleep. The purpose of this mini review was to summarize the evidence for validity of the most popular wrist-worn activity tracker (Fitbit) to estimate those health-related metrics in Parkinson disease. We researched full-length English studies in PubMed, Science Direct, Google Scholar, and Scopus, through September, 2021. In total, 27 studies and a textbook description were included in the review. To adapt consumer-wearable activity trackers for evaluating health-related metrics in Parkinson’s disease (PD) patients, there may be some points to be elucidated and conquered. First, measurement accuracy and precision are required. Second, inter-device reliability for measuring steps, distance, and energy expenditure must be considered. Third, wearability: there are some types of device such as wrist-worn, ankle-worn, belt-fixed, and so on. Overall, Fitbit has advantage for these points. This mini review indicates that Fitbit has enough measurement accuracy and precision to estimate health-related metrics of PD patients including amount of step, physical activity energy expenditure, and quality of sleep.
 
</p></abstract><kwd-group><kwd>Parkinson Disease</kwd><kwd> Consumer-Wearable Activity Trackers</kwd><kwd> Fitbit</kwd><kwd> Physical Activity</kwd><kwd> Sleep</kwd></kwd-group></article-meta></front><body><sec id="s1"><title>1. Introduction</title><p>There is consensus that physical activity has important for human brain health at any age [<xref ref-type="bibr" rid="scirp.114042-ref1">1</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref2">2</xref>]. Sustainably and regularly conducting physical activity is recommended as a non-pharmacologic therapy for maintaining general health status. For example, habitual exercise improves cardiorespiratory fitness and cardiovascular health, helps reducing body mass index, and can be effective for cardiovascular disease, for high blood pressure, and for brain dysfunctions [<xref ref-type="bibr" rid="scirp.114042-ref3">3</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref4">4</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref5">5</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref6">6</xref>]. In addition, there is growing evidence for the beneficial effects of physical activity on several diseases, including neurodegenerative diseases [<xref ref-type="bibr" rid="scirp.114042-ref4">4</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref6">6</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref7">7</xref>]. To promote or maintain physical activity, self-monitoring usingpedometers and accelerometers have been considered effective [<xref ref-type="bibr" rid="scirp.114042-ref8">8</xref>]. However, the validity of estimating the amount of physical activity or physical activity energy expenditure detected using consumer-wearable activity trackers has not been sufficiently established [<xref ref-type="bibr" rid="scirp.114042-ref9">9</xref>]. In addition, advent of mobile health technologies makes it possible to wear or to carry devices during daily activities. Among those devices, some can detect sleep pattern that also disturbed among neurodegenerative diseases [<xref ref-type="bibr" rid="scirp.114042-ref10">10</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref11">11</xref>]. Thus, consumer-wearable activity trackers for assessment of neurodegenerative diseases are required at least to evaluate physical activity, energy consumption, and quality of sleep.</p><p>Among neurodegenerative diseases, Parkinson’s disease is the most popular disease that is characterized by resting tremor, bradykinesia, rigidity, and a series of non-motor symptoms, including sleep disorders, depression, pain, constipation, and genitourinary problems [<xref ref-type="bibr" rid="scirp.114042-ref12">12</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref13">13</xref>]. To assess, motor signs and non-motor signs, only some questionnaires, such as Unified Parkinson’s Disease Rating Scale (UPDRS) [<xref ref-type="bibr" rid="scirp.114042-ref13">13</xref>] have been used for evaluation. And consumer-wearable activity trackers have possibility conveniently and rationally to evaluate these disabilities in PD patients. However, most of released consumer-wearable activity trackers are made for sports activity and are hardly to detect slow movement dominantly observed in PD patients [<xref ref-type="bibr" rid="scirp.114042-ref14">14</xref>].</p><p>Although growing amount of consumer-wearable activity trackers have been sold in consumer market, about the reasons why described in text, we selected Fitbit. Why was Fitbit suitable for evaluating PD patients? Pradhan [<xref ref-type="bibr" rid="scirp.114042-ref17">17</xref>] suggested that PD patients had reduced quantity and intensity of physical activities compared to healthy older adults, so the consumer-wearable activity trackers should have ability to detect small amount and low intensity activities of physical activities. Fitbit has such a character.</p><p>Mechanism of Fitbit to track health metrics.</p><p>In Fitbit Health Solutions, they [<xref ref-type="bibr" rid="scirp.114042-ref16">16</xref>] note that Fitbit offers devices that track a variety of metrics, including step count, floors climbed, distance, calories burned, active minutes, sleep time and stages, and heart rate.</p><p>To determine subject’s heart rate, the optical heart-rate sensor in the Fitbit device flashes its green LEDs many times per second and uses light-sensitive photodiodes to detect these capillary volume changes in the capillaries above the wrist. Then, the device calculates how many times subject’s heartbeats are per minute (bpm).</p><p>Fitbit devices use a 3-axis accelerometer to count steps. This sensor also allows the device to determine the frequency, duration, intensity, and patterns of movement (<xref ref-type="fig" rid="fig1">Figure 1</xref>).</p><p>Fitbit devices combine subject’s basal metabolic rate (BMR) and activity data to estimate calories burned. Adding heart-rate data can estimate calories burned during exercise.</p><p>Fitbit estimates subject’s sleep stages using a combination of movement and heart rate patterns. When subject haven’t moved for about an hour, tracker or watch assumes that subject is asleep. Additional data—such as the length of time subject’s movements are indicative of sleep behavior (such as rolling over, etc.) help confirm that subject is asleep. While sleeping, subject’s device tracks the beat-to-beat changes in heart rate, known as heart rate variability (HRV), which fluctuate as subject transition between light sleep, deep sleep, and REM sleep stages (<xref ref-type="fig" rid="fig2">Figure 2</xref>).</p><p>In this mini review, we summarize the evidence for validity of the most popular consumer-wearable activity tracker (Fitbit) to estimate the amount of physical activity, physical activity energy expenditure, and quality of sleep in Parkinson’s disease.</p></sec><sec id="s2"><title>2. Methods</title><p>We researched full-length English studies in PubMed, Science Direct, Google Scholar, and Scopus, through September, 2021.</p></sec><sec id="s3"><title>3. Results</title><p>In total, 27 studies and a textbook description [<xref ref-type="bibr" rid="scirp.114042-ref16">16</xref>] were included in the review.</p><p>To adapt consumer-wearable activity trackers for evaluating health-related metrics in Parkinson’s disease (PD) patients, there may be some points to be elucidated and conquered. First, measurement accuracy and precision are required. Second, inter-device reliability for measuring steps, distance, and energy expenditure must be considered. Third, wearability; there are some types of</p><p>device such as wrist-worn, ankle-worn, belt-fixed, and so on [<xref ref-type="bibr" rid="scirp.114042-ref17">17</xref>].</p><p>Evenson [<xref ref-type="bibr" rid="scirp.114042-ref14">14</xref>] summarized the evidence for validity and reliability of Fitbit and Jawbone and their ability to estimate steps, distance, physical activity, energy expenditure, and sleep. Evenson pointed that Fitbit had tendency to over-estimate at slower speeds and to under-estimate at faster speeds. This superficial weakness of Fitbit is conversely advantage to detect slow movements in PD. Measurement of energy consumption was tended to under-estimate by either device. Total sleep time and sleep efficiency were over-estimated and wake after sleep onset was under-estimated comparing metrics from polysomnography to either tracker. Paul [<xref ref-type="bibr" rid="scirp.114042-ref18">18</xref>] studied to determine the criterion validity of Fitbit step counts compared to visual count and ActiGraph accelerometer step counts in community-dwelling older people during a 2 min walk test (2 MWT). Their results indicated that percentage agreement was closest for Fitbit steps compared to visual count and least for Fitbit average steps/day compared to the ActiGraph. They concluded that Fitbit is sufficiently accurate to be used among community-dwelling older adults to monitor and give feedback on step counts. Price [<xref ref-type="bibr" rid="scirp.114042-ref19">19</xref>] estimated energy expenditure data measurement from four consumer-wearable activity trackers and compared to measurement from indirect calorimetry. In their study energy expenditure estimates from the Fitbit correlated significantly with calorimetry across all gait speeds but did not with calorimetry across running speeds. Murakami [<xref ref-type="bibr" rid="scirp.114042-ref20">20</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref21">21</xref>] examined the validity of total energy expenditure estimated by 12 consumer-wearable activity trackers during 1 standardized day in a metabolic chamber and 15 free-living days using the doubly labeled water method. They concluded that accurate estimations of the net physical activity energy expenditure using consumer-wearable activity trackers are required.</p><p>Kim [<xref ref-type="bibr" rid="scirp.114042-ref22">22</xref>] raised a question that wrist monitors were likely to overestimate activity; however, they used ActiGraph accelerometers, not consumer-based wearable devises. Pradhan [<xref ref-type="bibr" rid="scirp.114042-ref15">15</xref>] pointed wrist wearable devises had enough ability to detect steps and physical activities. Wendel [<xref ref-type="bibr" rid="scirp.114042-ref23">23</xref>] described that waist-worn activity trackers might monitor continuous walking with reasonable accuracy comparing with wrist-worn ones. Larmont [<xref ref-type="bibr" rid="scirp.114042-ref24">24</xref>] compared Fitbit with the other device and Fitbit had advantage in independency of intensity of activity and concluded that these wrist-worn devices might be a clinically useful adjunct to exercise therapy to increase physical activity in people with PD.</p><p>Xue [<xref ref-type="bibr" rid="scirp.114042-ref25">25</xref>] raised possibility of detecting nocturnal hypokinesia in PD using multisite inertial sensors. De Zambotti [<xref ref-type="bibr" rid="scirp.114042-ref9">9</xref>] evaluated the performance of Fitbit, against polysomnography (PSG) and concluded that Fitbit showed promise in detecting sleep-wake states and sleep stage composition relative to gold standard PSG, particularly in the estimation of REM sleep. Non-motor symptoms especially sleep disturbances, along with motor symptoms can be biomarkers to predict PD development [<xref ref-type="bibr" rid="scirp.114042-ref26">26</xref>].</p><p>Only evaluated ability to detect steps, physical activities and energy expenditures, but some authors raised applicability of consumer-based wearable devises for evaluating treatment effect in PD patients. Alley [<xref ref-type="bibr" rid="scirp.114042-ref27">27</xref>] using The Timed Up and Go test (TUG) suggested possibility to measure individual mobility in PD patients. Kleiner [<xref ref-type="bibr" rid="scirp.114042-ref28">28</xref>] tested a wearable device and showed excellent reliability, accuracy and precision in quantifying total TUG test duration. Since TUG is a widely used test in rehabilitation settings, its automatic quantification could potentially improve the quality of assessments in the quantification of PD gait ability [<xref ref-type="bibr" rid="scirp.114042-ref29">29</xref>]. Lai [<xref ref-type="bibr" rid="scirp.114042-ref30">30</xref>] comparatively evaluated three consumer-grade motion sensors in measuring steps with over ground and treadmill walking in PD and concluded that the waist-worn sensor (Fitbit One) was accurate and precise. Suppa [<xref ref-type="bibr" rid="scirp.114042-ref31">31</xref>] or Pulliam [<xref ref-type="bibr" rid="scirp.114042-ref32">32</xref>] assessed levodopa response in PD with wearable systems and availed comprehensive results. Col&#243;n-Semenza [<xref ref-type="bibr" rid="scirp.114042-ref33">33</xref>] developed a remote peer coaching using Fitbit and concluded that was feasible, safe, and acceptable for PD patients. However, as Alley [<xref ref-type="bibr" rid="scirp.114042-ref27">27</xref>] described that the lack of web-based physical activity interventions for the older may be due to the stereotype that older adults are low internet users and therefore do not engage in web-based health program. Mercer [<xref ref-type="bibr" rid="scirp.114042-ref34">34</xref>] compared four consumer-wearable activity trackers (Fitbit Zip, Misct Shine, Jawbone Up 24, and Withings Pulse) and asked which device was preferable. Preferences varied but 50% felt they would buy a Fitbit and 42% felt they would buy a Misct, Jawbone, or Withings. This suggests Fitbit may be acceptable device for older adults. To improve usability, older users may be select from devices that have better compatibility with personal computers or less-expensive Android mobile phones or iPhone and tablets. And they prefer devices with comprehensive paper-based user manuals and with applications that interpret user data. PD patients may unfamiliar with IoT and may need support to both set up the device and learn how to interpret their data. Wrist-worn wearable activity trackers including Fitbit can fulfill their requirement.</p></sec><sec id="s4"><title>4. Discussion</title><p>During a standard clinical evaluation, patient’s motor symptoms are visually assessed by clinicians while the individual performs specific tasks such as holding their arms outstretched, tapping their fingers, or tapping their toes [<xref ref-type="bibr" rid="scirp.114042-ref13">13</xref>]. Measuring PD symptoms during activities of daily living create an entirely new set of challenges for wearable sensors and algorithms. Not only must the system be intelligent enough to detect symptoms and side effects, but also it must be able to distinguish those from activities of daily living [<xref ref-type="bibr" rid="scirp.114042-ref35">35</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref36">36</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref37">37</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref38">38</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref39">39</xref>]. This comment is hallmark of assessment PD patient’s motor and nonmotor signs and symptoms by using consumer-wearable activity trackers.</p><p>Motion sensors are common today in wearables, watches, and mobile devices for monitoring exercise or general step counts. These gross measures of movement, however, do not provide a direct measure of PD features such as tremor, bradykinesia, or dyskinesia, as each of those symptoms have very distinct features and determine PD diagnosis. Actually, Apple watch got US patent (US number 20190365286) for providing continuous monitoring of dyskinesia and tremors, which could help clinicians, treat PD better. Apple’s claims that dyskinesia and tremors tend to occur when all of the other features of PD are being well managed through medication. Bai [<xref ref-type="bibr" rid="scirp.114042-ref40">40</xref>] [<xref ref-type="bibr" rid="scirp.114042-ref41">41</xref>] compared Apple Watch with Fitbit. Apple Watch had an advantage in detecting heart rate in aerobic exercise, but PD patients tended to show slow activities. However, since different devices have different measurement characteristics, a lack of standardization with accelerometry-based monitors has made it hard to advance applications for both research and practice. Consensus guidelines are needed for clinical application of consumer-wearable activity trackers.</p><p>Continuous and objective monitoring of motor and non-motor symptoms is needed to complement clinical assessments and patient reported outcomes. Such consumer-wearable activity trackers with rational algorithm could offer an objective measure for PD diagnosis and symptoms assessment, provide patients with a tool to monitor and track their disease, and give physicians a more thorough understanding of experience with PD patients, outside the clinic.</p></sec><sec id="s5"><title>5. Conclusion</title><p>This mini review indicated Fitbit could estimate the amount of step, physical activity, physical activity energy expenditure, and quality of sleep in PD patients. As new activity trackers and features have been introduced to the market, documentation of the measurement properties can guide their use in PD research settings. And physical activities may also improve quality of life in PD patients.</p></sec><sec id="s6"><title>Funding</title><p>No external funding sources.</p></sec><sec id="s7"><title>Conflicts of Interest</title><p>The author declares that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.</p></sec><sec id="s8"><title>Cite this paper</title><p>Abe, K. (2021) Can We Use Consumer-Wearable Activity Tracker Fitbit in Parkinson Disease? Advances in Parkinson’s Disease, 10, 15-23. https://doi.org/10.4236/apd.2021.102002</p></sec></body><back><ref-list><title>References</title><ref id="scirp.114042-ref1"><label>1</label><mixed-citation publication-type="other" xlink:type="simple">Erickson, K.I., Hillman, C., Stillman, C.M., Ballard, R.M., Bloodgood, B., Conroy, D.E., et al. (2019) Physical Activity, Cognition, and Brain Outcomes: A Review of the 2018 Physical Activity Guidelines. Medicine &amp; Science in Sports &amp; Exercise, 51, 1242-1251. https://doi.org/10.1249/MSS.0000000000001936</mixed-citation></ref><ref id="scirp.114042-ref2"><label>2</label><mixed-citation publication-type="other" xlink:type="simple">Hamer, M. and Chida, Y. (2009) Physical Activity and Risk of Neurodegenerative Disease; A Systematic Review of Prospective Evidence. Psychological Medicine, 39, 3-11. https://doi.org/10.1017/S0033291708003681</mixed-citation></ref><ref id="scirp.114042-ref3"><label>3</label><mixed-citation publication-type="other" xlink:type="simple">Rêgo, M.L., Cabral, D.A., Costa, E.C. and Fontes, E.B. (2019) Physical Exercise for Individuals with Hypertension: It Is Time to Emphasize Its Benefits on the Brain and Cognition. Clinical Medicine Insights: Cardiology, 13. https://doi.org/10.1177/1179546819839411</mixed-citation></ref><ref id="scirp.114042-ref4"><label>4</label><mixed-citation publication-type="other" xlink:type="simple">Di Liegro, C.M., Schiera, G., Proia, P. and Di Liegro, I. (2011) Physical Activity and Brain Health. Genes, 10, 720. https://doi.org/10.3390/genes10090720</mixed-citation></ref><ref id="scirp.114042-ref5"><label>5</label><mixed-citation publication-type="other" xlink:type="simple">Lee, J. (2018) The Relationship between Physical Activity and Dementia: A Systematic Review and Meta-Analysis of Prospective Cohort Studies. Journal of Gerontological Nursing, 44, 22-29. https://doi.org/10.3928/00989134-20180814-01</mixed-citation></ref><ref id="scirp.114042-ref6"><label>6</label><mixed-citation publication-type="other" xlink:type="simple">Séverine, S., Aline, D., Jean-Fran&amp;#231;ois, D., Jessica, A., Alexis, E., Mika, K., et al. (2017) Physical Activity, Cognitive Decline and Risk of Dementia: 28 Year Follow-Up of Whitehall II Cohort Study. BMJ, 357, j2709. https://doi.org/10.1136/bmj.j2709</mixed-citation></ref><ref id="scirp.114042-ref7"><label>7</label><mixed-citation publication-type="other" xlink:type="simple">Jiménez-Pavón, D., Carbonell-Baeza, A. and Lavie, C.J. (2019) Promoting the Assessment of Physical Activity and Cardiorespiratory Fitness in Assessing the Role of Vascular Risk on Cognitive Decline in Older Adults. Frontiers in Physiology, 10, 670. https://doi.org/10.3389/fphys.2019.00670</mixed-citation></ref><ref id="scirp.114042-ref8"><label>8</label><mixed-citation publication-type="other" xlink:type="simple">Bravata, D.M., Smith-Spangler, C., Sundaram, V., Gienger, A.L., Lin, N., Lewis, R., et al. (2007) Using Pedometers to Increase Physical Activity and Improve Health: A Systematic Review. JAM, 298, 2296-2304. https://doi.org/10.1001/jama.298.19.2296</mixed-citation></ref><ref id="scirp.114042-ref9"><label>9</label><mixed-citation publication-type="other" xlink:type="simple">de Zambotti, M., Goldstone, A., Claudatos, S., Colrain, I.M. and Baker, F.C. (2018) A Validation Study of Fitbit Charge 2&amp;#8482; Compared with Polysomnography in Adults. Chronobiology International, 35, 465-476. https://doi.org/10.1080/07420528.2017.1413578</mixed-citation></ref><ref id="scirp.114042-ref10"><label>10</label><mixed-citation publication-type="other" xlink:type="simple">Conley, S., Knies, A., Batten, J., Ash, G., Miner, B., Hwang, Y., et al. (2019) Agreement between Actigraphic and Polysomnographic Measures of Sleep in Adults with and without Chronic Conditions: A Systematic Review and Meta-Analysis. Sleep Medicine Reviews, 46, 151-160. https://doi.org/10.1016/j.smrv.2019.05.001</mixed-citation></ref><ref id="scirp.114042-ref11"><label>11</label><mixed-citation publication-type="other" xlink:type="simple">Postuma, R.B., Berg, D., Stern, M., Poewe, W., Olanow, C.W., Oertel, W., et al. (2015) MDS Clinical Diagnostic Criteria for Parkinson’s Disease. Movement Disorders, 30, 1591-601. https://doi.org/10.1002/mds.26424</mixed-citation></ref><ref id="scirp.114042-ref12"><label>12</label><mixed-citation publication-type="other" xlink:type="simple">Chaudhuri, K.R., Healy, D.G. and Schapira, A.H.V. (2006) Nonmotor Symptoms of Parkinson’s Disease: Diagnosis and Management. The Lancet Neurology, 5, 235-245. https://doi.org/10.1016/S1474-4422(06)70373-8</mixed-citation></ref><ref id="scirp.114042-ref13"><label>13</label><mixed-citation publication-type="book" xlink:type="simple">Fahn, S., et al. (1987) Unified Parkinson’s Disease Rating Scale. In: Fahn, S., et al., Eds., Recent Developments in Parkinson’s Disease, Volume II, Macmillan Healthcare Information, Florham Park, 153-163.</mixed-citation></ref><ref id="scirp.114042-ref14"><label>14</label><mixed-citation publication-type="other" xlink:type="simple">Evenson, K.R., Goto, M.M. and Furberg, R.D. (2015) Systematic Review of the Validity and Reliability of Consumer-Wearable Activity Trackers. International Journal of Behavioral Nutrition and Physical Activity, 12, 159-180. https://doi.org/10.1186/s12966-015-0314-1</mixed-citation></ref><ref id="scirp.114042-ref15"><label>15</label><mixed-citation publication-type="other" xlink:type="simple">Pradhan, S. and Kelly, V.E. (2019) Quantifying Physical Activity in Early Parkinson Disease Using a Commercial Activity Monitor. Parkinsonism &amp; Related Disorders, 66, 171-175. https://doi.org/10.1016/j.parkreldis.2019.08.001</mixed-citation></ref><ref id="scirp.114042-ref16"><label>16</label><mixed-citation publication-type="other" xlink:type="simple">https://healthsolutions.fitbit.com/researchers/faqs</mixed-citation></ref><ref id="scirp.114042-ref17"><label>17</label><mixed-citation publication-type="other" xlink:type="simple">Dey, N., Chaki, J. and Kumar, R. (2019) Sensors for Health Monitoring. Academic Press, Cambridge.</mixed-citation></ref><ref id="scirp.114042-ref18"><label>18</label><mixed-citation publication-type="other" xlink:type="simple">Paul, S.S., Tiedemann, A., Hassett, L.M., Ramsay, E., Kirkham, C., Chagpar, S., et al. (2015) Validity of the Fitbit Activity Tracker for Measuring Steps in Community-Dwelling Older Adults. BMJ Open Sport &amp; Exercise Medicine, 1, e000013. https://doi.org/10.1136/bmjsem-2015-000013</mixed-citation></ref><ref id="scirp.114042-ref19"><label>19</label><mixed-citation publication-type="other" xlink:type="simple">Price, K., Bird, S.R., Lythgo, N., Raj, I.S., Wong, J.Y. and Lynch, C. (2017) Validation of the Fitbit One, Garmin Vivofit and Jawbone UP Activity Tracker in Estimation of Energy Expenditure during Treadmill Walking and Running. Journal of Medical Engineering &amp; Technology, 41, 208-215. https://doi.org/10.1080/03091902.2016.1253795</mixed-citation></ref><ref id="scirp.114042-ref20"><label>20</label><mixed-citation publication-type="other" xlink:type="simple">Murakami, H., Kawakami, R., Nakae, S., Nakata, Y., Ishikawa-Takata, K., Tanaka, S., et al. (2016) Accuracy of Wearable Devices for Estimating Total Energy Expenditure: Comparison with Metabolic Chamber and Doubly Labeled Water Method. JAMA Internal Medicine, 176, 702-703. https://doi.org/10.1001/jamainternmed.2016.0152</mixed-citation></ref><ref id="scirp.114042-ref21"><label>21</label><mixed-citation publication-type="other" xlink:type="simple">Murakami, H., Kawakami, R., Nakae, S., Nakata, Y., Ohkawara, K., Sasai, H., et al. (2019) Accuracy of 12 Wearable Devices for Estimating Physical Activity Energy Expenditure Using a Metabolic Chamber and the Doubly Labeled Water Method: Validation Study. JMIR mHealth and uHealth, 7, e13938. https://doi.org/10.2196/13938</mixed-citation></ref><ref id="scirp.114042-ref22"><label>22</label><mixed-citation publication-type="other" xlink:type="simple">Kim, D.W., Hassett, L.M., Nguy, V. and Allen, N.E. (2019) A Comparison of Activity Monitor Data from Devices Worn on the Wrist and the Waist in People with Parkinson’s Disease. Movement Disorders Clinical Practice, 6, 693-699. https://doi.org/10.1002/mdc3.12850</mixed-citation></ref><ref id="scirp.114042-ref23"><label>23</label><mixed-citation publication-type="other" xlink:type="simple">Wendel, N., Macpherson, C.E., Webber, K., Hendron, K., DeAngelis, T., Colon-Semenza, C., et al. (2018) Accuracy of Activity Trackers in Parkinson Disease: Should We Prescribe Them? Physical Therapy, 98, 705-714. https://doi.org/10.1093/ptj/pzy054</mixed-citation></ref><ref id="scirp.114042-ref24"><label>24</label><mixed-citation publication-type="other" xlink:type="simple">Lamont, R.M., Daniel, H.L., Payne, C.L. and Brauer, S.G. (2018) Accuracy of Wearable Physical Activity Trackers in People with Parkinson’s Disease. Gait &amp; Posture, 63, 104-108. https://doi.org/10.1016/j.gaitpost.2018.04.034</mixed-citation></ref><ref id="scirp.114042-ref25"><label>25</label><mixed-citation publication-type="other" xlink:type="simple">Xue, F., Wang, F.-Y., Mao, C.-J., Guo, S.P., Chen, J., Li, J., et al. (2018) Analysis of Nocturnal Hypokinesia and Sleep Quality in Parkinson’s Disease. Journal of Clinical Neuroscience, 54, 96-101. https://doi.org/10.1016/j.jocn.2018.06.016</mixed-citation></ref><ref id="scirp.114042-ref26"><label>26</label><mixed-citation publication-type="other" xlink:type="simple">Rees, R.N., Noyce, A.J. and Schrag, A. (2019) The Prodromes of Parkinson’s Disease. European Journal of Neuroscience, 49, 320-327. https://doi.org/10.1111/ejn.14269</mixed-citation></ref><ref id="scirp.114042-ref27"><label>27</label><mixed-citation publication-type="other" xlink:type="simple">Alley, S., vanUffelen, J.G.Z., Schoeppe, S., Parkinson, L., Hunt, S., Power, D., et al. (2019) Efficacy of a Computer-Tailored Web-Based Physical Activity Intervention Using Fitbits for Older Adults: A Randomised Controlled Trial Protocol. BMJ Open, 9, e033305. https://doi.org/10.1136/bmjopen-2019-033305</mixed-citation></ref><ref id="scirp.114042-ref28"><label>28</label><mixed-citation publication-type="other" xlink:type="simple">Kleiner, A.F.R., Pacifici, I., Vagnini, A., Camerota, F., Celletti, C., Stocchi, F., et al. (2018) Timed Up and Go Evaluation with Wearable Devices: Validation in Parkinson’s Disease. Journal of Bodywork and Movement Therapies, 22, 390-395. https://doi.org/10.1016/j.jbmt.2017.07.006</mixed-citation></ref><ref id="scirp.114042-ref29"><label>29</label><mixed-citation publication-type="other" xlink:type="simple">Shumway-Cook, A., Brauer, S. and Woollacott, M. (2001) Predicting the Probability for Falls in Community-Dwelling Older Adults Using the Timed Up &amp; Go Test. Physical Therapy, 81, 1060-1061.</mixed-citation></ref><ref id="scirp.114042-ref30"><label>30</label><mixed-citation publication-type="other" xlink:type="simple">Lai, B., Sasaki, J.E., Jeng, B., Cederberg, K.L., Bamman, M.M. and Motl, R.W. (2020) Accuracy and Precision of Three Consumer-Grade Motion Sensors during Overground and Treadmill Walking in People with Parkinson Disease: Cross-Sectional Comparative Study. JMIR Rehabilitation and Assistive Technologies, 16, e14059. https://doi.org/10.2196/14059</mixed-citation></ref><ref id="scirp.114042-ref31"><label>31</label><mixed-citation publication-type="other" xlink:type="simple">Suppa, A., Kita, A., Leodori, G., Zampogna, A., Nicolini, E., Lorenzi, P., et al. (2017) L-DOPA and Freezing of Gait in Parkinson’s Disease: Objective Assessment through a Wearable Wireless System. Frontiers in Neurology, 8, 406-439. https://doi.org/10.3389/fneur.2017.00406</mixed-citation></ref><ref id="scirp.114042-ref32"><label>32</label><mixed-citation publication-type="other" xlink:type="simple">Pulliam, C.L., Heldman, D.A., Brokaw, E.B., Mera, T.O., Mari, Z.K. and Burack, M.A. (2017) Continuous Assessment of Levodopa Response in Parkinson’s Disease Using Wearable Motion Sensors. IEEE Transactions on Biomedical Engineering, 65, 159-164. https://doi.org/10.1109/TBME.2017.2697764</mixed-citation></ref><ref id="scirp.114042-ref33"><label>33</label><mixed-citation publication-type="other" xlink:type="simple">Colón-Semenza, C., Latham, N.K., Quintiliani, L.M. and Ellis, T.D. (2018) Peer Coaching through mHealth Targeting Physical Activity in People with Parkinson Disease: Feasibility Study. JMIR mHealth and uHealth, 6, e42. https://doi.org/10.2196/mhealth.8074</mixed-citation></ref><ref id="scirp.114042-ref34"><label>34</label><mixed-citation publication-type="other" xlink:type="simple">Mercer, K., Giangregorio, L., Schneider, E., Chilana, P., Li, M. and Grindrod, K. (2016) Acceptance of Commercially Available Wearable Activity Trackers among Adults Aged over 50 and with Chronic Illness: A Mixed-Methods Evaluation. JMIR mHealth and uHealth, 4, e7. https://doi.org/10.2196/mhealth.4225</mixed-citation></ref><ref id="scirp.114042-ref35"><label>35</label><mixed-citation publication-type="other" xlink:type="simple">Gallagher, W. (2019) Future Apple Watch May Help Treat Parkinson’s Disease or Diagnose Tremor Symptoms. Appleinsider.</mixed-citation></ref><ref id="scirp.114042-ref36"><label>36</label><mixed-citation publication-type="other" xlink:type="simple">Welk, G.J., Bai, Y., Lee, J.M., Godino, J., Saint-Maurice, P.F. and Carr, L. (2019) Standardizing Analytic Methods and Reporting in Activity Monitor Validation Studies. Medicine &amp; Science in Sports &amp; Exercise, 51, 1767-1780. https://doi.org/10.1249/MSS.0000000000001966</mixed-citation></ref><ref id="scirp.114042-ref37"><label>37</label><mixed-citation publication-type="other" xlink:type="simple">Artusi, C.A., Imbalzano, G., Sturchio, A., Pilotto, A., Montanaro, E., Padovani, A., Lopiano, L., Maetzler, W. and Espay, A.J. (2020) Implementation of Mobile Health Technologies in Clinical Trials of Movement Disorders: Underutilized Potential. Neurotherapeutics, 17, 1736-1746. https://doi.org/10.1007/s13311-020-00901-x</mixed-citation></ref><ref id="scirp.114042-ref38"><label>38</label><mixed-citation publication-type="other" xlink:type="simple">Sokas, D., Paliakait&amp;#279;, B., Rapalis, A., Marozas, V., Bailón, R. and Petr&amp;#279;nas, A. (2021) Detection of Walk Tests in Free-Living Activities Using a Wrist-Worn Device. Frontiers in Physiology, 12, Article ID: 706545. https://doi.org/10.3389/fphys.2021.706545</mixed-citation></ref><ref id="scirp.114042-ref39"><label>39</label><mixed-citation publication-type="other" xlink:type="simple">Cederberg, K.L.J., Jeng, B., Sasaki, J.E., Lai, B., Bamman, M. and Motl, R.W. (2021) Accuracy and Precision of Wrist-Worn Actigraphy for Measuring Steps Taken during Over-Ground and Treadmill Walking in Adults with Parkinson’s Disease. Parkinsonism &amp; Related Disorders, 88, 102-107. https://doi.org/10.1016/j.parkreldis.2021.06.009</mixed-citation></ref><ref id="scirp.114042-ref40"><label>40</label><mixed-citation publication-type="other" xlink:type="simple">Bai, Y., Hibbing, P., Mantis, C. and Welk, G.J. (2018) Comparative Evaluation of Heart Rate-Based Monitors: Apple Watch vs Fitbit Charge HR. Journal of Sports Sciences, 36, 1734-1741. https://doi.org/10.1080/02640414.2017.1412235</mixed-citation></ref><ref id="scirp.114042-ref41"><label>41</label><mixed-citation publication-type="other" xlink:type="simple">Bai, Y., Tompkins, C., Gell, N., Dione, D., Zhang, T. and Byun, W. (2021) Comprehensive Comparison of Apple Watch and Fitbit Monitors in a Free-Living Setting. PLoS ONE, 16, e0251975. https://doi.org/10.1371/journal.pone.0251975</mixed-citation></ref></ref-list></back></article>