A multi-sensor wearable system for the assessment of diseased gait in real-world conditions.

Introduction: Accurately assessing people's gait, especially in real-world conditions and in case of impaired mobility, is still a challenge due to intrinsic and extrinsic factors resulting in gait complexity. To improve the estimation of gait-related digital mobility outcomes (DMOs) in real-world scenarios, this study presents a wearable multi-sensor system (INDIP), integrating complementary sensing approaches (two plantar pressure insoles, three inertial units and two distance sensors). Methods: The INDIP technical validity was assessed against stereophotogrammetry during a laboratory experimental protocol comprising structured tests (including continuous curvilinear and rectilinear walking and steps) and a simulation of daily-life activities (including intermittent gait and short walking bouts). To evaluate its performance on various gait patterns, data were collected on 128 participants from seven cohorts: healthy young and older adults, patients with Parkinson's disease, multiple sclerosis, chronic obstructive pulmonary disease, congestive heart failure, and proximal femur fracture. Moreover, INDIP usability was evaluated by recording 2.5-h of real-world unsupervised activity. Results and discussion: Excellent absolute agreement (ICC >0.95) and very limited mean absolute errors were observed for all cohorts and digital mobility outcomes (cadence ≤0.61 steps/min, stride length ≤0.02 m, walking speed ≤0.02 m/s) in the structured tests. Larger, but limited, errors were observed during the daily-life simulation (cadence 2.72-4.87 steps/min, stride length 0.04-0.06 m, walking speed 0.03-0.05 m/s). Neither major technical nor usability issues were declared during the 2.5-h acquisitions. Therefore, the INDIP system can be considered a valid and feasible solution to collect reference data for analyzing gait in real-world conditions.

The Potential of Transcranial Alternating Current Stimulation to Alleviate Dual-Task Gait Costs in Older Adults: Insights from a Double-Blinded Pilot Study.

BACKGROUND: The performance of an attention-demanding task while walking, i.e., dual-tasking, leads to dual-task costs (e.g., reduced gait speed) in older adults. Previous studies have shown that dual-task costs in gait are associated with future falls and cognitive decline. According to the communication through coherence hypothesis, transcranial alternating current stimulation (tACS) might help alleviate this problem. OBJECTIVE: The aim of this study was to examine the effects of a single session of theta-tACS targeting the left fronto-parietal network (L-FPN) on dual-task walking and cognitive function compared to sham stimulation and transcranial direct current stimulation (tDCS) targeting the left dorsolateral prefrontal cortex, a node within the L-FPN. METHODS: Twenty older adults completed a four-visit, double-blinded, within-subject, cross-over study in which usual-walking, dual-task walking, and cognitive function were evaluated before and immediately after 20 min of tACS, tDCS, or sham (order randomized) stimulation. Dual-task costs to gait speed (primary outcome) and other measures were analyzed. RESULTS: The dual-task cost to gait speed tended to be lower (i.e., better) after tACS (p = 0.067, Cohen's d = 0.433∼small); tDCS significantly reduced this dual-task cost (p = 0.012, Cohen's d = 0.618∼medium), and sham stimulation had no effect (p = 0.467). tACS significantly reduced the dual-task cost to step length (p = 0.037, Cohen's d = 0.502∼medium); a trend was seen after tDCS (p = 0.069, Cohen's d = 0.443∼small). No statistical differences were found for other measures of gait or cognitive function. CONCLUSIONS: The positive effects of tACS on dual-task gait speed and step length were roughly similar to those seen with tDCS. These results suggest that tACS affects the fronto-parietal network and, similar to tDCS, tACS may improve dual-tasking. Nonetheless, to achieve larger benefits and differentiate the effects of tACS and tDCS on brain function and dual-task walking in older adults, other stimulation montages and protocols should be tested.

Connecting real-world digital mobility assessment to clinical outcomes for regulatory and clinical endorsement-the Mobilise-D study protocol.

BACKGROUND: The development of optimal strategies to treat impaired mobility related to ageing and chronic disease requires better ways to detect and measure it. Digital health technology, including body worn sensors, has the potential to directly and accurately capture real-world mobility. Mobilise-D consists of 34 partners from 13 countries who are working together to jointly develop and implement a digital mobility assessment solution to demonstrate that real-world digital mobility outcomes have the potential to provide a better, safer, and quicker way to assess, monitor, and predict the efficacy of new interventions on impaired mobility. The overarching objective of the study is to establish the clinical validity of digital outcomes in patient populations impacted by mobility challenges, and to support engagement with regulatory and health technology agencies towards acceptance of digital mobility assessment in regulatory and health technology assessment decisions. METHODS/DESIGN: The Mobilise-D clinical validation study is a longitudinal observational cohort study that will recruit 2400 participants from four clinical cohorts. The populations of the Innovative Medicine Initiative-Joint Undertaking represent neurodegenerative conditions (Parkinson's Disease), respiratory disease (Chronic Obstructive Pulmonary Disease), neuro-inflammatory disorder (Multiple Sclerosis), fall-related injuries, osteoporosis, sarcopenia, and frailty (Proximal Femoral Fracture). In total, 17 clinical sites in ten countries will recruit participants who will be evaluated every six months over a period of two years. A wide range of core and cohort specific outcome measures will be collected, spanning patient-reported, observer-reported, and clinician-reported outcomes as well as performance-based outcomes (physical measures and cognitive/mental measures). Daily-living mobility and physical capacity will be assessed directly using a wearable device. These four clinical cohorts were chosen to obtain generalizable clinical findings, including diverse clinical, cultural, geographical, and age representation. The disease cohorts include a broad and heterogeneous range of subject characteristics with varying chronic care needs, and represent different trajectories of mobility disability. DISCUSSION: The results of Mobilise-D will provide longitudinal data on the use of digital mobility outcomes to identify, stratify, and monitor disability. This will support the development of widespread, cost-effective access to optimal clinical mobility management through personalised healthcare. Further, Mobilise-D will provide evidence-based, direct measures which can be endorsed by regulatory agencies and health technology assessment bodies to quantify the impact of disease-modifying interventions on mobility. TRIAL REGISTRATION: ISRCTN12051706.

Targeted tDCS Mitigates Dual-Task Costs to Gait and Balance in Older Adults.

OBJECTIVE: Among older adults, the ability to stand or walk while performing cognitive tasks (ie, dual-tasking) requires coordinated activation of several brain networks. In this multicenter, double-blinded, randomized, and sham-controlled study, we examined the effects of modulating the excitability of the left dorsolateral prefrontal cortex (L-DLPFC) and the primary sensorimotor cortex (SM1) on dual-task performance "costs" to standing and walking. METHODS: Fifty-seven older adults without overt illness or disease completed 4 separate study visits during which they received 20 minutes of transcranial direct current stimulation (tDCS) optimized to facilitate the excitability of the L-DLPFC and SM1 simultaneously, or each region separately, or neither region (sham). Before and immediately after stimulation, participants completed a dual-task paradigm in which they were asked to stand and walk with and without concurrent performance of a serial-subtraction task. RESULTS: tDCS simultaneously targeting the L-DLPFC and SM1, as well as tDCS targeting the L-DLPFC alone, mitigated dual-task costs to standing and walking to a greater extent than tDCS targeting SM1 alone or sham (p < 0.02). Blinding efficacy was excellent and participant subjective belief in the type of stimulation received (real or sham) did not contribute to the observed functional benefits of tDCS. INTERPRETATION: These results demonstrate that in older adults, dual-task decrements may be amenable to change and implicate L-DPFC excitability as a modifiable component of the control system that enables dual-task standing and walking. tDCS may be used to improve resilience and the ability of older results to walk and stand under challenging conditions, potentially enhancing everyday functioning and reducing fall risks. ANN NEUROL 2021;90:428-439.

Sensor-Based and Patient-Based Assessment of Daily-Living Physical Activity in People with Parkinson's Disease: Do Motor Subtypes Play a Role?

The benefits of daily-living physical activity are clear. Nonetheless, the relationship between physical activity levels and motor subtypes of Parkinson's disease (PD), i.e., tremor dominant (TD) and postural instability gait difficulty (PIGD), have not been well-studied. It is also unclear if patient perspectives and motor symptom severity are related to objective, sensor-based assessment of daily-living activity in those subtypes. To address these questions, total daily-living physical activity was quantified in 73 patients with PD and 29 healthy controls using a 3D-accelerometer worn on the lower back for at least three days. We found that individuals with the PIGD subtype were significantly less active than healthy older adults (p = 0.007), unlike individuals with the TD subtype. Among the PIGD subtype, higher daily physical activity was negatively associated with more severe ON bradykinesia (rS = -0.499, p = 0.002), motor symptoms (higher ON MDS-UPDRS (Unified Parkinson's Disease Rating Scale motor examination)-III scores), gait difficulties (rS = -0.502, p = 0.002), motor complications (rS = 0.466, p = 0.004), and balance (rS = 0.519, p = 0.001). In contrast, among the TD subtype, disease-related characteristics were not related to daily-living physical activity. Intriguingly, physical activity was not related to self-report of ADL difficulties (scores of the MDS-UPDRS Parts I or II) in both motor subtypes. These findings highlight the importance of objective daily-living physical activity monitoring and suggest that self-report does not necessarily reflect objective physical activity levels. Furthermore, the results point to important differences in factors related to physical activity in PD motor subtypes, setting the stage for personalized treatment programs.

Long-term unsupervised mobility assessment in movement disorders.

Mobile health technologies (wearable, portable, body-fixed sensors, or domestic-integrated devices) that quantify mobility in unsupervised, daily living environments are emerging as complementary clinical assessments. Data collected in these ecologically valid, patient-relevant settings can overcome limitations of conventional clinical assessments, as they capture fluctuating and rare events. These data could support clinical decision making and could also serve as outcomes in clinical trials. However, studies that directly compared assessments made in unsupervised and supervised (eg, in the laboratory or hospital) settings point to large disparities, even in the same parameters of mobility. These differences appear to be affected by psychological, physiological, cognitive, environmental, and technical factors, and by the types of mobilities and diagnoses assessed. To facilitate the successful adaptation of the unsupervised assessment of mobility into clinical practice and clinical trials, clinicians and researchers should consider these disparities and the multiple factors that contribute to them.

A roadmap for implementation of patient-centered digital outcome measures in Parkinson's disease obtained using mobile health technologies.

Obtaining reliable longitudinal information about everyday functioning from individuals with Parkinson's disease (PD) in natural environments is critical for clinical care and research. Despite advances in mobile health technologies, the implementation of digital outcome measures is hindered by a lack of consensus on the type and scope of measures, the most appropriate approach for data capture (eg, in clinic or at home), and the extraction of timely information that meets the needs of patients, clinicians, caregivers, and health care regulators. The Movement Disorder Society Task Force on Technology proposes the following objectives to facilitate the adoption of mobile health technologies: (1) identification of patient-centered and clinically relevant digital outcomes; (2) selection criteria for device combinations that offer an acceptable benefit-to-burden ratio to patients and that deliver reliable, clinically relevant insights; (3) development of an accessible, scalable, and secure platform for data integration and data analytics; and (4) agreement on a pathway for approval by regulators, adoption into e-health systems and implementation by health care organizations. We have developed a tentative roadmap that addresses these needs by providing the following deliverables: (1) results and interpretation of an online survey to define patient-relevant endpoints, (2) agreement on the selection criteria for use of device combinations, (3) an example of an open-source platform for integrating mobile health technology output, and (4) recommendations for assessing readiness for deployment of promising devices and algorithms suitable for regulatory approval. This concrete implementation guidance, harmonizing the collaborative endeavor among stakeholders, can improve assessments of individuals with PD, tailor symptomatic therapy, and enhance health care outcomes. © 2019 International Parkinson and Movement Disorder Society.

The Discriminant Value of Phase-Dependent Local Dynamic Stability of Daily Life Walking in Older Adult Community-Dwelling Fallers and Nonfallers.

The present study compares phase-dependent measures of local dynamic stability of daily life walking with 35 conventional gait features in their ability to discriminate between community-dwelling older fallers and nonfallers. The study reanalyzes 3D-acceleration data of 3-day daily life activity from 39 older people who reported less than 2 falls during one year and 31 who reported two or more falls. Phase-dependent local dynamic stability was defined for initial perturbation at 0%, 20%, 40%, 60%, and 80% of the step cycle. A partial least square discriminant analysis (PLS-DA) was used to compare the discriminant abilities of phase-dependent local dynamic stability with the discriminant abilities of 35 conventional gait features. The phase-dependent local dynamic stability λ at 0% and 60% of the step cycle discriminated well between fallers and nonfallers (AUC = 0.83) and was significantly larger (p < 0.01) for the nonfallers. Furthermore, phase-dependent λ discriminated as well between fallers and nonfallers as all other gait features combined. The present result suggests that phase-dependent measures of local dynamic stability of daily life walking might be of importance for further development in early fall risk screening tools.

Comparative assessment of different methods for the estimation of gait temporal parameters using a single inertial sensor: application to elderly, post-stroke, Parkinson's disease and Huntington's disease subjects.

The estimation of gait temporal parameters with inertial measurement units (IMU) is a research topic of interest in clinical gait analysis. Several methods, based on the use of a single IMU mounted at waist level, have been proposed for the estimate of these parameters showing satisfactory performance when applied to the gait of healthy subjects. However, the above mentioned methods were developed and validated on healthy subjects and their applicability in pathological gait conditions was not systematically explored. We tested the three best performing methods found in a previous comparative study on data acquired from 10 older adults, 10 hemiparetic, 10 Parkinson's disease and 10 Huntington's disease subjects. An instrumented gait mat was used as gold standard. When pathological populations were analyzed, missed or extra events were found for all methods and a global decrease of their performance was observed to different extents depending on the specific group analyzed. The results revealed that none of the tested methods outperformed the others in terms of accuracy of the gait parameters determination for all the populations except the Parkinson's disease subjects group for which one of the methods performed better than others. The hemiparetic subjects group was the most critical group to analyze (stride duration errors between 4-5 % and step duration errors between 8-13 % of the actual values across methods). Only one method provides estimates of the stance and swing durations which however should be interpreted with caution in pathological populations (stance duration errors between 6-14 %, swing duration errors between 10-32 % of the actual values across populations).

Objective assessment of fall risk in Parkinson's disease using a body-fixed sensor worn for 3 days.

BACKGROUND: Patients with Parkinson's disease (PD) suffer from a high fall risk. Previous approaches for evaluating fall risk are based on self-report or testing at a given time point and may, therefore, be insufficient to optimally capture fall risk. We tested, for the first time, whether metrics derived from 3 day continuous recordings are associated with fall risk in PD. METHODS AND MATERIALS: 107 patients (Hoehn & Yahr Stage: 2.6±0.7) wore a small, body-fixed sensor (3D accelerometer) on lower back for 3 days. Walking quantity (e.g., steps per 3-days) and quality (e.g., frequency-derived measures of gait variability) were determined. Subjects were classified as fallers or non-fallers based on fall history. Subjects were also followed for one year to evaluate predictors of the transition from non-faller to faller. RESULTS: The 3 day acceleration derived measures were significantly different in fallers and non-fallers and were significantly correlated with previously validated measures of fall risk. Walking quantity was similar in the two groups. In contrast, the fallers walked with higher step-to-step variability, e.g., anterior-posterior width of the dominant frequency was larger (p = 0.012) in the fallers (0.78 ± 0.17 Hz) compared to the non-fallers (0.71 ± 0.07 Hz). Among subjects who reported no falls in the year prior to testing, sensor-derived measures predicted the time to first fall (p = 0.0034), whereas many traditional measures did not. Cox regression analysis showed that anterior-posterior width was significantly (p = 0.0039) associated with time to fall during the follow-up period, even after adjusting for traditional measures. CONCLUSIONS/SIGNIFICANCE: These findings indicate that a body-fixed sensor worn continuously can evaluate fall risk in PD. This sensor-based approach was able to identify transition from non-faller to faller, whereas many traditional metrics were not successful. This approach may facilitate earlier detection of fall risk and may in the future, help reduce high costs associated with falls.

Balance testing with inertial sensors in patients with Parkinson's disease: assessment of motor subtypes.

In this study, the use of an instrumented balance test based on inertial sensors was evaluated in patients with Parkinson's disease (PD). We aimed to objectively characterize motor subtypes of PD [tremor dominant (TD) and postural instability gait difficulty (PIGD)], to help to quantitatively classify the PD subjects into motor subtypes. Subjects were studied performing postural tests, while wearing a device including a tri-axial accelerometer on the lower back, in four different experimental conditions that depended on feet position (feet-together or semi-tandem) and vision (eyes open or closed). Postural measures, after a reliability check, were tested to identify their sensitivity to the disease, to the PD subtypes, and to the experimental conditions. The results highlight the possibility of distinguishing between the TD and PIGD subtypes by means of objective postural measures that are able to detect tremor and PIGD features and are able to classify a subject as TD or PIGD with good accuracy. Feet position influences frequency measures, whereas eyes closure influences the displacement measures and enhances differences between PD and control subjects, suggesting that postural displacement measures may be capable of detecting different adaptation processes to external sensory conditions between patients with PD and control subjects.

Toward automated, at-home assessment of mobility among patients with Parkinson disease, using a body-worn accelerometer.

OBJECTIVE: To develop an automated and objective method to assess mobility in Parkinson disease (PD) patients in daily-life settings and to investigate whether accelerometer-derived measures discriminate between PD and healthy controls as they walk and simulate activities of daily living (ADL). METHODS: Healthy older adults (17) and patients with PD (22) wore a triaxial accelerometer on their lower back during short walks (validation study) and during a walk around the medical center to simulate daily activities (ADL simulation). The variability (consistency and rhythmicity) of stepping was assessed. The patients completed the walks before and after taking their anti-Parkinsonian medications. Frequency-based acceleration measures included dominant frequency, amplitude (strength of signal frequency), width (frequency dispersion), and slope (a combination reflecting amplitude and width) of the main frequency of the power spectral density in the 0.5- to 3.0-Hz band. A subset of the Unified Parkinson-Disease Rating Scale provided a clinical measure of gait impairment (UPDRS-Gait5). A PD patient and control wore the sensors for 3 days at home. RESULTS: The width was larger, and the amplitude and slope were smaller in the PD patients compared to the controls in the validation study and ADL simulation (P < .02). The width decreased, and the amplitude and slope increased when patients took anti-Parkinsonian medications (P < .007). Significant correlations were observed between acceleration-derived measures and UPDRS-Gait5. The data obtained at home was similar to the clinic data. CONCLUSIONS: Frequency-derived measures are valid and sensitive estimates of stride-to-stride variability that can be used to assess the quality and consistency of walking in patients with PD in real-life settings.

The Dynamic Gait Index in healthy older adults: the role of stair climbing, fear of falling and gender.

The Dynamic Gait Index (DGI) was developed as a clinical tool to assess gait, balance and fall risk. Because the DGI evaluates not only usual steady-state walking, but also walking during more challenging tasks, it may be an especially sensitive test. The present investigation evaluated the DGI and its association with falls, fear of falling, depression, anxiety and other measures of balance and mobility in 278 healthy elderly individuals. Measures included the DGI, the Berg Balance Test (BBT), the Timed Up and Go (TUAG), the Mini-Mental State Exam (MMSE), the Unified Parkinson's Disease Rating Scale (UPDRS) motor part, the Activities-specific Balance Confidence (ABC) scale and the number of annual falls. The DGI was moderately correlated with the BBT (r=0.53; p<0.001), the TUAG (r=-0.42; p<0.001) and the ABC (r=0.49; p<0.001). Fallers performed worse on the DGI compared to non-fallers (p=0.029). Scores on the DGI were near perfect in men (23.3+/-1.2), but among women, there was a small, but significant (p<0.001) decrease (22.5+/-1.6). The reduction in the DGI score in women was due to stair climbing performance, with many women (65%) choosing to walk while holding a handrail, compared to only 39% of men. Scores on the BBT, the TUAG, the UPDRS and the MMSE were similar in men and women. Conversely, ABC scores and fall history were different. These findings suggest that the DGI, although susceptible to ceiling effects, appears to be an appropriate tool for assessing function in healthy older adults.

A novel multidomain computerized cognitive assessment for attention-deficit hyperactivity disorder: evidence for widespread and circumscribed cognitive deficits.

Multidomain assessment may enhance the diagnosis of cognitive impairment in children with attention-deficit hyperactivity disorder (ADHD). A set of novel Web-enabled computerized tests has recently been shown to be valid for identifying mild cognitive impairment and characterizing the cognitive profile associated with various disorders. It was anticipated that these tests would be well suited for use in children with ADHD. The authors tested this idea in a pilot study of 15 children (12 males, 3 females; mean age, 11 years 10 months; range, 9-15 years) with ADHD and 15 age-, education-, and gender-matched controls. The profile of cognitive impairment in ADHD children off methylphenidate across 6 cognitive domains (memory, executive function, visual-spatial skills, verbal function, attention, and motor skills) was described relative to controls. The effect of treatment with methylphenidate was examined by comparing the ADHD children on methylphenidate and on placebo (administered in a double-blind randomized fashion) relative to controls and by comparing the ADHD children on methylphenidate relative to placebo. Significant impairment in ADHD was evident in memory, visual-spatial, verbal, and attention domains, and near-significant impairment was observed in executive function and motor skills. On methylphenidate but not placebo, performance was comparable to controls in immediate verbal memory, psychomotor accuracy, visual-spatial, verbal rhyming, and overall battery performance. Significant improvement with administration of methylphenidate relative to placebo was evident for psychomotor accuracy, verbal rhyming, and overall battery performance. Hence, on the limited basis of this pilot study, the set of computerized tests studied appears to be useful for measuring cognitive function in ADHD; however, additional studies are needed to confirm this.

Falls and freezing of gait in Parkinson's disease: a review of two interconnected, episodic phenomena.

Falls and freezing of gait are two "episodic" phenomena that are common in Parkinson's disease. Both symptoms are often incapacitating for affected patients, as the associated physical and psychosocial consequences have a great impact on the patients' quality of life, and survival is diminished. Furthermore, the resultant loss of independence and the treatment costs of injuries add substantially to the health care expenditures associated with Parkinson's disease. In this clinically oriented review, we summarise recent insights into falls and freezing of gait and highlight their similarities, differences, and links. Topics covered include the clinical presentation, recent ideas about the underlying pathophysiology, and the possibilities for treatment. A review of the literature and the current state-of-the-art suggests that clinicians should not feel deterred by the complex nature of falls and freezing of gait; a careful clinical approach may lead to an individually tailored treatment, which can offer at least partial relief for many affected patients.