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Functional dependency in basic activities of daily living (ADLs) is a key outcome in Parkinson's disease (PD). We aimed to define dependency in PD, using the original and MDS versions of the Unified Parkinson's Disease Rating Scale (UPDRS).We developed two algorithms to define dependency from items of UPDRS Part 2 and MDS-UPDRS Part 2 relating to basic ADLs (feeding, dressing, hygiene and walking, and getting out of a chair). We validated both algorithms using data from 1110 patients from six community-based PD incidence cohorts, testing concurrent validity, convergent validity, and predictive validity.Our optimal algorithm showed high specificity and moderate to high sensitivity versus SchwabEngland80% (specificity 95% [95% confidence interval (CI) 93-97] and sensitivity 65% [95% CI 55-73] at baseline; 88% [95% CI 85-91] and 85% [95% CI 79-97] respectively at five-years follow-up). Convergent validity was demonstrated by strong associations between dependency defined by the algorithm and cognition (MMSE), quality of life (PDQ39), and impairment (UPDRS part 3) (all p 0.001). Algorithm-defined dependency status also predicted mortality: HR for mortality in those dependent vs independent at baseline was 1.6 (95%CI 1.2-2.1) and in those dependent vs independent at five-years' follow-up was 2.2 (1.6-3.0).We have demonstrated the concurrent validity, convergent validity, and predictive validity of a UPDRS-/MDS-UPDRS-based algorithm to define functional dependency in PD. This can be used for studying dependency in any study where UPDRS or MDS-UPDRS part 2 data have been collected.

The ability to perceive differences in environmental contrast is critical for navigating complex environments safely. People with Parkinson's disease (PD) report a multitude of visual and cognitive deficits which may impede safe obstacle negotiation and increase fall risk. Enhancing obstacle contrast may influence the content of visual information acquired within complex environments and thus target environmental fall risk factors. 17 PD with a history of falls and 18 controls walked over an obstacle covered in a high and low contrast material in separate trials whilst eye movements were recorded. Measures of visual function and cognition were obtained. Gaze location was extracted during the approach phase. PD spent longer looking at the obstacle compared to controls regardless of contrast (p .05), however group differences were largest for the low contrast obstacle. When accounting for group differences in approach time, PD spent longer looking at the low contrast obstacle and less time looking at the ground beyond the low contrast obstacle compared to controls (p .05). The response to obstacle contrast in PD (high-low) was significantly associated with executive function. Better executive function was associated with spending longer looking at the low contrast obstacle and at the ground beyond the high contrast obstacle. Enhancing the contrast of ground-based trip hazards may improve visual processing of environmental cues in PD, particularly for individuals with better executive function. Manipulating contrast to attract visual attention is already in use in the public domain, however its utility for reducing fall risk in PD is yet to be formally tested in habitual settings.

Background\ud Changes in upper body (UB) motion during gait may be a marker of incipient pathology, intervention response and disease progression in Parkinson’s disease (PD), which if independent from the lower body motion, might provide an improved assessment of gait.\ud \ud Research question\ud This study aimed to test this hypothesis and establish whether variables calculated from accelerations measured on the UB are unique from spatiotemporal characteristics and can contribute to an improved classification of PD gait.\ud \ud Methods\ud Data was obtained from 70 people with PD (69.2 ± 9.9 y.o., UPDRS III: 36.9 ± 12.3) and 64 age-matched controls (71.6 ± 6.8 y.o.). Spatiotemporal characteristics were measured using a pressure sensitive mat (GAITRite). Head and pelvis accelerations were synchronously measured with wearable inertial sensors (Opal, APDM). Pearson’s product-moment correlations were calculated between 49 selected variables from UB accelerations (representing magnitude, smoothness, regularity, symmetry and attenuation) and 16 traditional spatiotemporal characteristics (representing pace, variability, rhythm, asymmetry and postural control). Univariate and multivariate regression analysis was used to test the variables ability to classify PD gait.\ud \ud Results\ud The variables were mostly unique from each other (67% of variables recorded an r

Background: Mobility is defined as the ability to independently move around the environment and is a key contributor to quality of life. The aim of this study was to evaluate the use of mobility as a decisive outcome for the marketing authorisation of drugs by the European Medicines Agency (EMA). Methods: Fifteen therapeutic areas which commonly lead to mobility impairments and alter the quantity and/or the quality of walking were selected: two systemic neurological diseases, four conditions primarily affecting exercise capacity, seven musculoskeletal diseases, and two conditions representing sensory impairments. European Public Assessment Reports (EPARs) published by the EMA up to September 2020 were examined for mobility endpoints included in their ‘main studies’, defined as those which were decisive for EU approval. Clinical study registries and primary scientific publications for these studies were also reviewed. Findings: 484 EPARs yielded 186 relevant documents with 402 ‘main studies’. The EPARs reported 153 primary and 584 secondary endpoints which considered mobility; 70 different assessment tools (38 patient-reported outcomes, 13 clinician-reported outcomes, 8 performance outcomes, and 13 composite endpoints) were used. Importantly, only 15·7% of those tools distinctly informed on patients’ mobility status. 105/402 (26·1%) of the ‘main studies’ did not have any mobility assessment and none of these studies included a digital mobility outcome. The supplementary review of study registries and primary publications revealed only five uses of mobility assessments not reported by EPARs. Interpretation: For conditions with a high impact on mobility, distinct mobility assessment was given little consideration in the marketing authorisation of drugs by the EMA. Where mobility impairment was considered to be a relevant outcome, questionnaires or composite scores were predominantly used. Reporting biases for such outcomes presents challenges for the interpretation of study results. Funding: Mobilise-D (Innovative Medicines Initiative) and Robert Bosch Stiftung, Germany. Declaration of Interest: SJ is partly supported by the Robert Bosch Stiftung Stuttgart. MW reports grants from HORIZON2020 IMI No. 820820, during the conduct of the study. DS reports grants from HORIZON2020 IMI No. 820820, during the conduct of the study. MC reports personal fees from Takeda Pharmaceuticals, during the conduct of the study; personal fees from Takeda Pharmaceuticals, outside the submitted work. JK reports grants from HORIZON2020 IMI No. 820820, during the conduct of the study. JGA reports grants from HORIZON2020 IMI No. 820820, and from AstraZeneca, Chiesi, Esteve, outside the submitted work. WM receives or received funding from the European Union, the German Federal Ministry of Education of Research, Michael J. Fox Foundation, Robert Bosch Foundation, Neuroalliance, Lundbeck and Janssen. He received speaker honoraria from Abbvie, Bayer, GlaxoSmithKline, Licher MT, Rolke Pharma and UCB, was invited to Advisory Boards of Abbvie, Biogen, Lundbeck and Market Access & Pricing Strategy GmbH, and is an advisory board member of the Critical Path for Parkinson's Consortium. He serves as the co-chair of the MDS Technology Task Force. MP reports grants from HORIZON2020 IMI No. 820820, outside the submitted work. MS is supported by the Robert Bosch Stiftung Stuttgart and reports grants from HORIZON2020 IMI 2 Mobilise D, during the conduct of the study, and grants and non-financial support from Green Cross WellBeing Co. Ltd., Gilead Sciences Inc., Robert Bosch GmbH, and CORAT Therapeutics GmbH , as well as other from Agena Bioscience GmbH, outside the submitted work. CB disclosed consultation from E. Lilly and speaker fees from Amgen, Nutricia and Pfizer reports grants from HORIZON2020 IMI No. 820820, during the conduct of the study. RT, BS, LL, LR, SCR declare no competing interests.

Background Postural instability is a common motor feature in people with Parkinson's disease (PD) together with non-motor features such as cognitive dysfunction. Management of postural instability is challenging as it is often resistant to dopaminergic therapy. Greater knowledge of postural control is essential to understand postural instability in PD. Research question This study aimed to answer how postural control differs in people with PD compared to healthy older adults (HOA). Additionally, postural control changes over a 36 month period and its relationship to cognitive impairment and motor scores were investigated. Methods The study group consisted of 50 people diagnosed with PD and 59 HOAs, recruited as part of an incident cohort study (ICICLE-GAIT). Participants stood still for 2 min, eyes open and arms by their side. A single tri-axial accelerometer (Axivity AX3, York, UK) on the lower back recorded acceleration. Measurements were taken at 18, 36 and 54 months after recruitment. Sample entropy (SampEn), which measures signal predictability, was determined for the accelerometry data. Cognitive tests included the Montreal Cognitive Assessment and the Unified Parkinson’s Disease Rating Scale (UPDRS III) quantified motor function. Linear mixed models, regression analysis and correlation analysis were applied to the data. Results indicated that SampEn was greater for the PD group at all three time-points and along all three axes. However, there was no increase of SampEn with disease progression. Higher SampEn values were associated with greater cognitive impairment and lower UPDRS III, although correlations were weak. There was a difference between axial directions and cognitive and motor scores. Significance People with PD exhibit decreased regularity of trunk dynamics when standing compared to HOAs. Nonlinear accelerometer metrics along all three axes are therefore a potential biomarker of PD. The relationship between trunk dynamics and cognitive function indicates common neural pathways.

Gait impairment places older adults and people with Parkinson's disease (PD) at an increased risk of falls when walking over obstacles. Increasing the height of obstacles results in greater challenge to balance however little is known about the demands encountered when negotiating obstacles of greater depth which may be greater for PD who often walk with a short, shuffling gait.To describe gait adaptation in older adults and people with PD when walking over long and tall obstacles.20 people with PD and 13 older adults with a history of falls walked across an instrumented walkway under four conditions: level walking, and over a small, long and tall obstacle. Differences due to group, step and obstacle type were evaluated using General Linear Models.An increased step duration, longer single limb support and a wider step (p .033) were observed when crossing the tall obstacle for both older adults and PD. The PD group completed the crossing steps more slowly than controls, with a shorter step and longer single limb support (p .043). Obstacle type did not significantly influence step length.The greatest temporal-spatial adaptations were elicited when participants negotiated the tall obstacle. Electing a wider step when crossing the tall obstacle was a strategy common to both faller groups (older adults and PD). The tall obstacle presented added challenge for PD who spent longer in single limb support during the crossing steps compared to controls. The long obstacle did not cause a disproportionate change in step length in people with PD, and we suggest that the obstacle may have acted as a visual cue in this group.

Physical impairments and activity restrictions cause significant morbidity after surgery for sarcoma. Yet objective assessment of key components of balance, gait and physical activity (PA), using valid and reliable outcome measures, is lacking in routine clinical practice.We therefore performed a systematic review to identify studies quantifying balance, gait and PA in clinically useful ways, after treatment for lower extremity sarcoma.Relevant articles quantifying balance, gait and PA in patients who underwent surgery for lower extremity bone or soft tissue sarcoma were identified from Medline, Embase, Scopus, and Web of Science up to February 2016. Results were compiled by principal research findings, objective measures used, their ability to detect differences between important clinical groups, change over time and reliability.Eighteen articles were included. Surgery had a significant impact on outcomes (p 0.05). A wide range of measures and concerns about accuracy of measurement were noted, as gait and PA measures did not discriminate between distinct clinical groups such as limb sparing surgery and amputation, and did not detect changes over time. Few studies investigated reliability (n = 1) and sensitivity to change (n = 4).There is a deficit of studies quantifying balance, gait and PA in patients with lower extremity sarcoma. Studies did not use consistent, valid and reliable instruments. There is an urgent need to develop novel objective measures of physical functioning in this patient group to encourage evidence-based clinical care.

Introduction\ud Current PD assessment methods have inherent limitations. There is need for an objective method to assist clinical decisions and to facilitate evaluation of treatments. Accelerometers, and analysis using artificial neural networks (ANN), have shown potential as a method of motor symptom evaluation. This work describes the development of a novel PD disease state detection system informed by algorithms based on data collected in an unsupervised, home environment. We evaluated whether this approach can reproduce patient-completed symptom diaries and clinical assessment of disease state.\ud \ud Methods\ud 34 participants with PD wore bilateral wrist-worn accelerometers for 4 h in a research facility (phase 1) and for 7 days at home whilst completing symptom diaries (phase 2). An ANN to predict disease state was developed based on home-derived accelerometer data. Using a leave-one-out approach, ANN performance was evaluated against patient-completed symptom diaries and against clinician rating of disease state.\ud \ud Results\ud In the clinical setting, specificity for dyskinesia detection was extremely high (0.99); high specificity was also demonstrated for home-derived data (0.93), but with low sensitivity (0.38). In both settings, sensitivity for on/off detection was sub-optimal. ANN-derived values of the proportions of time in each disease state showed strong, significant correlations with patient-completed symptom diaries.\ud \ud Conclusion\ud Accurate, real-time evaluation of symptoms in an unsupervised, home environment, with this sensor system, is not yet achievable. In terms of the amounts of time spent in each disease state, ANN-derived results were comparable to those of symptom diaries, suggesting this method may provide a valuable outcome measure for medication trials.

Background: Sleep interruptions and nocturnal hypokinesia are common in Parkinson's disease (PD). Pilot work using wearable technologies showed fewer nocturnal movements in patients with advanced PD compared to controls. However, the prevalence of these impairments in early stage of the disease and the influence of non-motor symptoms, and dopaminergic medication are unknown. Methods: This study evaluated wearable sensor data collected in 305 patients with PD at different Hohen and Yahr disease stages (HY HY H&Y3=77) and 205 healthy controls (HC). Subjects wore a tri-axial accelerometer continuously (24/7) on the lower back for at least 2 days. Percent upright-time and nighttime walking were defined based on the vertical axis of the acceleration signal and were classified as sleep interruptions. The number, velocity, time, side, and degree of rotations in bed during the night evaluated nocturnal movements. Findings: Nocturnal lying-time was similar between PD and controls (p=0.501), however, the number of turns and the turn velocity significantly decreased (p

Background Engaging aged residential care (ARC) residents with physical activity (PA) may be a useful strategy to decelerate dependence and disability. It is unclear what volume, intensity and patterns of PA ARC residents participate in. This review aims to synthesize the literature to quantify the volume, intensity and pattern of PA that ARC residents participate in across differing care levels (e.g. low, intermediate, high, mixed), and make recommendations for future research. Methods 30 studies of 48,760 yielded were reviewed using systematic review strategies. Results Questionnaires and technological tools were used to assess PA, with accelerometers employed in 70% of studies. Overall, studies reported low volumes and intensities of PA across all care levels, and suggested limited variation in patterns of PA (e.g. little day-to-day variation in total PA). There was limited inclusion of people with cognitive impairment, potentially causing representativeness bias. Findings were limited by lack of consistency in methodological approaches and PA outcomes. Discussion Based on findings and limitations of current research, we recommend that total volume or low-light intensity PA are more useful interventional outcomes than higher-intensity PA. Researchers also need to consider which methodology and PA outcomes are most useful to quantify PA in ARC residents.

Contains fulltext : 167962.pdf (Publisher’s version ) (Closed access) BACKGROUND: Age-associated motor and cognitive deficits increase the risk of falls, a major cause of morbidity and mortality. Because of the significant ramifications of falls, many interventions have been proposed, but few have aimed to prevent falls via an integrated approach targeting both motor and cognitive function. We aimed to test the hypothesis that an intervention combining treadmill training with non-immersive virtual reality (VR) to target both cognitive aspects of safe ambulation and mobility would lead to fewer falls than would treadmill training alone. METHODS: We carried out this randomised controlled trial at five clinical centres across five countries (Belgium, Israel, Italy, the Netherlands, and the UK). Adults aged 60-90 years with a high risk of falls based on a history of two or more falls in the 6 months before the study and with varied motor and cognitive deficits were randomly assigned by use of computer-based allocation to receive 6 weeks of either treadmill training plus VR or treadmill training alone. Randomisation was stratified by subgroups of patients (those with a history of idiopathic falls, those with mild cognitive impairment, and those with Parkinson's disease) and sex, with stratification per clinical site. Group allocation was done by a third party not involved in onsite study procedures. Both groups aimed to train three times per week for 6 weeks, with each session lasting about 45 min and structured training progression individualised to the participant's level of performance. The VR system consisted of a motion-capture camera and a computer-generated simulation projected on to a large screen, which was specifically designed to reduce fall risk in older adults by including real-life challenges such as obstacles, multiple pathways, and distracters that required continual adjustment of steps. The primary outcome was the incident rate of falls during the 6 months after the end of training, which was assessed in a modified intention-to-treat population. Safety was assessed in all patients who were assigned a treatment. This study is registered with ClinicalTrials.gov, NCT01732653. FINDINGS: Between Jan 6, 2013, and April 3, 2015, 302 adults were randomly assigned to either the treadmill training plus VR group (n=154) or treadmill training alone group (n=148). Data from 282 (93%) participants were included in the prespecified, modified intention-to-treat analysis. Before training, the incident rate of falls was similar in both groups (10.7 [SD 35.6] falls per 6 months for treadmill training alone vs 11.9 [39.5] falls per 6 months for treadmill training plus VR). In the 6 months after training, the incident rate was significantly lower in the treadmill training plus VR group than it had been before training (6.00 [95% CI 4.36-8.25] falls per 6 months; p

Recent research highlights the association of gait and cognition in older adults but a stronger understanding is needed to discern coincident pathophysiology, patterns of change, examine underlying mechanisms and aid diagnosis. This structured review mapped associations and predictors of gait and cognition in older adults with and without cognitive impairment, and Parkinson's disease. Fifty papers out of an initial yield of 22,128 were reviewed and a model of gait guided analysis and interpretation. Associations were dominated by the pace domain of gait; the most frequently studied domain. In older adults pace was identified as a predictor for cognitive decline. Where comprehensive measurement of gait was conducted, more specific pathological patterns of association were evident highlighting the importance of this approach. This review confirmed a robust association between gait and cognition and argues for a selective, comprehensive measurement approach. Results suggest gait may be a surrogate marker of cognitive impairment and cognitive decline. Understanding the specific nature of this relationship is essential for refinement of diagnostics and development of novel therapies.

The aim of this study was to assess the effect of varying the maximum resting period between consecutive ambulatory bouts in community-based outcomes. Ambulation was assessed in 97 community-dwelling older adults (mean (SD) age 69.2 (7.7) years) using an accelerometer (activPAL™) worn on the upper thigh for 7 consecutive days. The volume, pattern and variability of ambulation were calculated over a range of maximum resting periods (1–30 s). Outcomes with a maximum resting period from 1 to 6 s did not vary due to device functionality. Non-linear regression (power law, r2 > 0.99) showed that increasing the maximum resting period from 6 to 30 s resulted in changes in volume (increased duration spent walking, and decreased number of bouts), variability (S2 increased) and pattern (α decreased), and a linear relationship with an increase in average bout length. With a MRP of 6s, 6% of the cohort achieved the public health guidelines of 150 min of ambulation/week accumulated in bouts ≥10 min, which increased to 40% using a maximum resting period of 30 s. Modifying the maximum resting period impacts on volume, pattern and variability measures of community based ambulation, and attainment of public health guidelines. This highlights the need for standardised algorithms to aid interpretation and explicit reporting of the maximum resting period to aid comparison between studies.

Highlights • Instrumented testing of five physical capability tasks with a single accelerometer. • Evaluated on a large cohort of older adults. • iCap provides robust quantitative data about physical capability. • iCap captures gait and postural control data known as sensitive to ageing/pathology. • Methodology may have practical utility in a wide range of surveys and studies., Objectives The aims of this study were to (i) investigate instrumented physical capability (iCap) as a valid method during a large study and (ii) determine whether iCap can provide important additional features of postural control and gait to categorise cohorts not previously possible with manual recordings. Study design Cross-sectional analysis involving instrumented testing on 74 adults who were recruited as part of a pilot intervention study; LiveWell. Participants wore a single accelerometer-based monitor (lower back) during standardised physical capability tests so that outcomes could be compared directly with manual recordings (stopwatch and measurement tape) made concurrently. Main outcome measures Time, distance, postural control and gait characteristics. Results Agreement between manual and iCap ranged from moderate to excellent (0.649–0.983) with mean differences between methods low and deemed acceptable. Additionally, iCap successfully quantified (i) postural control characteristics which showed sensitivity to distinguish between 5 variations of the standing balance test and (ii) 14 gait characteristics known to be sensitive to age/pathology. Conclusions Our findings show that iCap can provide robust quantitative data about physical capability during standardised tests while also providing sensitive (age/pathology) postural control and gait characteristics not previously quantifiable with manual recordings. The methodology which we propose may have practical utility in a wide range of clinical and public health surveys and studies, including intervention studies, where assessment could be undertaken within diverse settings. This will need to be tested in further validation studies in a wider range of settings.

Highlights • Detailed investigation to explain poor variability/asymmetry agreement between accelerometers and instrumented walkway. • Caution is urged in the choice of reference system for validation studies. • Accelerometers have potential to gather continuous and robust spatio-temporal gait data, representative of normal living. • Further refinement of the gait algorithms are required., Gait is an important clinical assessment tool since changes in gait may reflect changes in general health. Measurement of gait is a complex process which has been restricted to the laboratory until relatively recently. The application of an inexpensive body worn sensor with appropriate gait algorithms (BWM) is an attractive alternative and offers the potential to assess gait in any setting. In this study we investigated the use of a low-cost BWM, compared to laboratory reference using a robust testing protocol in both younger and older adults. We observed that the BWM is a valid tool for estimating total step count and mean spatio-temporal gait characteristics however agreement for variability and asymmetry results was poor. We conducted a detailed investigation to explain the poor agreement between systems and determined it was due to inherent differences between the systems rather than inability of the sensor to measure the gait characteristics. The results highlight caution in the choice of reference system for validation studies. The BWM used in this study has the potential to gather longitudinal (real-world) spatio-temporal gait data that could be readily used in large lifestyle-based intervention studies, but further refinement of the algorithm(s) is required.

INTRODUCTION: Few studies have categorized falls in early Parkinson's disease (PD) and little is known about falls incidence and evolution. Fall incidence and frequency are reported to be 'U' shaped with respect to disease severity and may be influenced by time spent engaged in ambulatory activity. METHODS: Twelve months prospective falls in an incident PD cohort (n = 111) were reported and the relationship between falls and ambulatory activity was examined in a subgroup (n = 83). Fall events were collected using standardised protocols and were categorized by fall frequency (non-faller, single fall, recurrent falls) and also by a novel classification based on pre-fall event: (1) engaged in advanced activity; (2) ambulation; and (3) transition. Non-parametric statistics compared groups in both classifications. RESULTS: At baseline 23 (20.7%) of the cohort had fallen, increasing to 41 (36.9%) participants over 12 months. Total time spent walking was significantly lower for transition fallers compared with non-fallers and ambulation fallers (p = 0.041), who also had significantly increased disease severity. There were no significant relationships when fallers were categorized by frequency. We present an inverted U curve model depicting the relationship between falls and activity over time in PD, and propose that at this stage transition and ambulation fallers occupy different places on the curve. CONCLUSIONS: Falls are more common than recognised in newly-diagnosed PD. Daily activity is reduced even in early disease for people who fall during transitions. Classification methods that take pre-fall event into account may be useful to understand the heterogeneity of this complex problem. Language: en

BackgroundThe Microsoft Kinect sensor (Kinect) is potentially a low-cost solution for clinical and home-based assessment of movement symptoms in people with Parkinson's disease (PD). The purpose of this study was to establish the accuracy of the Kinect in measuring clinically relevant movements in people with PD.MethodsNine people with PD and 10 controls performed a series of movements which were measured concurrently with a Vicon three-dimensional motion analysis system (gold-standard) and the Kinect. The movements included quiet standing, multidirectional reaching and stepping and walking on the spot, and the following items from the Unified Parkinson's Disease Rating Scale: hand clasping, finger tapping, foot, leg agility, chair rising and hand pronation. Outcomes included mean timing and range of motion across movement repetitions.ResultsThe Kinect measured timing of movement repetitions very accurately (low bias, 95% limits of agreement 0.9 and Pearson's r>0.9). However, the Kinect had varied success measuring spatial characteristics, ranging from excellent for gross movements such as sit-to-stand (ICC=.989) to very poor for fine movement such as hand clasping (ICC=.012). Despite this, results from the Kinect related strongly to those obtained with the Vicon system (Pearson's r>0.8) for most movements.ConclusionsThe Kinect can accurately measure timing and gross spatial characteristics of clinically relevant movements but not with the same spatial accuracy for smaller movements, such as hand clasping.

Dual-task interference during gait is a common phenomenon in older adults and people with Parkinson’s disease (PD). Dual-task performance is driven by cognitive processes involving executive function, attention and working memory which underpin resource capacity and allocation. The underlying processes that contribute to dual-task interference are poorly understood, and confounded by methodological differences. The aim of this study was to explore the nature of dual-task interference in PD with respect to age-matched controls. We examined 121 people with early PD and 189 controls and controlled for baseline task demand on both tasks allowing between-group differences to be attributed to dual-task interference rather than differences in baseline performance. We also compared a wide range of gait characteristics to evaluate the pattern of interference. Participants walked for two minutes at a preferred pace under single- and dual-task (test of working memory capacity − digit span recall) conditions. In a subgroup task demand was increased (digit span + 1) (n = 55 control, n = 44 PD) to assess the influence of resource capacity. Finally the association between dual-task interference with motor and cognitive characteristics was examined to evaluate resource capacity and allocation. PD and controls responded similarly to the dual-task for all gait characteristics except for step width and step width variability and this was the same when task demand increased (dual + 1). Control participants took wider steps (p = 0.006) and step width variability increased significantly for controls (p = 0.001) but not PD. Interference was specific to the gait characteristic rather than a global pattern of impairment. Digit span error rates were not significantly different between groups during dual-task performance. There were no significant correlations with dual-task interference and global cognition, motor deficit, and executive function for either group. Effects of dual-tasks on gait performance are twofold and specific to the gait characteristic. They reflect an age-related reduction in gait performance (especially forward progression) in PD and controls possibly due to reduced resource capacity; and secondly, show postural stability during walking in early PD is disproportionately affected highlighting a PD-specific dual-task co-ordination deficit. Further work is required to identify the cognitive, executive and motor correlates of dual-task interference from which inferences about underlying cognitive processes can be made. These findings inform an understanding of dual-task impairment in early PD and suggest that management should target postural control under dual-task conditions from the early stages.

Background Despite the widespread use of gait variability in research and clinical studies, testing protocols designed to optimise its reliability have not been established. This study evaluates the impact of testing protocol and pathology on the reliability of gait variability. Objective To (i) estimate the reliability of gait variability during continuous and intermittent walking protocols in older adults and people with Parkinson's disease (PD), (ii) determine optimal number of steps for acceptable levels of reliability of gait variability and (iii) provide sample size estimates for use in clinical trials. Methods Gait variability was measured twice, one week apart, in 27 older adults and 25 PD participants. Participants walked at their preferred pace during: (i) a continuous 2 min walk and (ii) 3 intermittent walks over a 12 m walkway. Gait variability was calculated as the within-person standard deviation for step velocity, length and width, and step, stance and swing duration. Results Reliability of gait variability ranged from poor to excellent (intra class correlations .041–.860; relative limits of agreement 34–89%). Gait variability was more reliable during continuous walks. Control and PD participants demonstrated similar reliability. Increasing the number of steps improved reliability, with most improvement seen across the first 30 steps. Conclusions In this study, we identified testing protocols that improve the reliability of measuring gait variability. We recommend using a continuous walking protocol and to collect no fewer than 30 steps. Early PD does not appear to impact negatively on the reliability of gait variability.

Motor and cognitive processes are required for successful 'real world' walking. We explored the specific contribution of motor function, executive function, and attention to functional gait performance in people with Parkinson's Disease (PD) when 'off' medication. Twenty-nine people with PD wearing an accelerometer were tested in their home whilst walking under four task conditions. Explanatory characteristics included age, motor function, executive function, sustained attention and divided attention. Repeated measures ANOVA compared gait speed under different task conditions. Multiple regression analysis explored the effect of characteristics on gait speed and gait interference (difference between dual and single task). Gait performance deteriorated under complex conditions (F=51.0, P

The striatum is very much involved in learning motor sequences particularly in the consolidation phase, predicting that motor learning is affected in Parkinson's disease (PD). We conducted a literature review on this question and showed that behavioural studies indicate a relatively preserved acquisition as well as retention of motor learning in PD. Persons with PD did demonstrate slower learning-rates than controls. Brain imaging studies highlighted that much more brain activity is needed and different neural networks are recruited in PD, suggesting a reduced efficiency of learning. Using additional sensory information may optimize motor learning in PD. There is abundant evidence that cueing helps to achieve better movement performance and that these effects are retained immediately after withdrawal, possibly indicating the first signs of consolidation. Also, automatization of cued learning was demonstrated, as cues not only enhanced dual-task performance but these increments were retained after cue withdrawal. However, the effect of longer periods of cued training on retention of cued and uncued performance is not well established and some studies suggest that learning effects may be cue-dependent. The results of this review support the notion that adopting motor learning principles could benefit rehabilitation in PD. Even so, the limitations of reduced flexibility, efficiency and increased context-specificity of motor learning in PD need to be taken into account.

Freezing of gait (FOG) is difficult to measure due to its unpredictable occurrence. This study investigated: (1) whether the new freezing of gait questionnaire (NFOG-Q) is a reliable measure of freezing by comparing patients' ratings with those of carers' and (2) whether adding a video improved its reliability. Non-demented people with Parkinson's disease (PD) (N=102) and their carers of similar age and cognitive status were recruited from movement disorders clinics in three countries. The NFOG-Q was administered to carers and patients independently before and after watching a video showing several examples of FOG. Patients had very high agreement between their pre- and post-video detection of FOG (Kappa=0.91). However, this was less than in carers (Kappa=0.79). The video had a significant influence (p=0.01) on the rating of FOG severity (duration) but not on the estimation of its functional impact. Post-video freezing severity scores in the 69 freezers showed high agreement with carers' scores (ICC=0.78 [0.65;0.87]). We conclude that the NFOG-Q is a reliable tool to detect and evaluate the impact and severity of FOG. Adding a video does not add to the sensitivity and specificity of FOG detection but influences the estimation of FOG severity.

Baker K, Rochester L, Nieuwboer A. The immediate effect of attentional, auditory, and a combined cue strategy on gait during single and dual tasks in Parkinson's disease. Objective To compare the effect of rhythmic auditory and attentional cues, and a combination of both cues on gait, in people with Parkinson's disease (PD) during single and dual tasks. Design A repeated-measures study requiring participants to perform single and dual-motor tasks under different cueing conditions. Setting Human movement analysis laboratory. Participants Fifteen participants with idiopathic PD and a comparison group of 12 healthy participants. Interventions Three cueing strategies were compared: a rhythmic auditory cue (walking in time to a metronome beat), an attentional strategy (asked to focus on taking big step), and a combination cue (asked to walk in time to a metronome beat while taking big steps). Main Outcome Measures Walking speed, step amplitude, and step frequency. Results Walking speed of PD participants improved significantly compared with noncued walking in the single- and dual-task condition with the attentional ( P P =.037) and combination cue strategies ( P =.013, P =.028). Step amplitude also increased significantly with the attentional and combination cue strategies in single- ( P P P P P =.042) in the single and dual tasks ( P P =.009) in the dual task. The rhythmic auditory cue alone did not alter significantly any parameter of gait in the single or dual tasks. Conclusions The attentional strategy and the combination of a rhythmic auditory cue with an attentional strategy were equally effective, and improved walking speed and step amplitude significantly during both single and dual tasks. The combination cue, however, may still be a useful alternative in situations of increased attentional demand, or where problems exist with executive function.

Rochester L, Hetherington V, Jones D, Nieuwboer A, Willems AM, Kwakkel G, Van Wegen E. The effect of external rhythmic cues (auditory and visual) on walking during a functional task in homes of people with Parkinson's disease. Objectives To evaluate (1) the influence of rhythmic cues on gait interference during a functional activity and (2) the relationship of clinical symptoms to gait interference. Design Repeated-measures study. Setting Participants' homes. Participants Twenty subjects with idiopathic Parkinson's disease (PD) and a control group of 10 age-, sex-, and education-matched subjects. Interventions Subjects performed a simple functional task that included a walking component and a dual-motor task. The functional task was performed with and without external rhythmic (auditory and visual) cues. Main outcome measures Walking speed, mean step length, and step frequency were compared during trials of the tasks. In addition, tests of cognitive executive function (Hayling and Brixton tests), anxiety and depression (Hospital Anxiety and Depression Scale), and fatigue (Multidimensional Fatigue Inventory) were undertaken. Results The use of auditory cues during a dual task involving gait reduced the interference effect on the task; significant increases in step length were observed in PD subjects ( P =.018), representing an increase of 19%. Conclusions External auditory cues may be useful in reducing interference and maintaining gait performance during more complicated functional activities. Clinical symptoms, such as depression and fatigue, could influence the ability to focus attention and may increase gait interference during the performance of complex tasks, with subsequent implications for functional walking and safety.

Rochester L, Hetherington V, Jones D, Nieuwboer A, Willems A-M, Kwakkel G, Van Wegen E. Attending to the task: interference effects of functional tasks on walking in Parkinson's disease and the roles of cognition, depression, fatigue, and balance. Arch Phys Med Rehabil 2004;85:1578–85. Objective To evaluate the interference effects on walking of functional activities in the home in people with Parkinson's disease (PD) and the contribution of clinical symptoms to disturbance of gait. Design A repeated-measures trial, using a dual-task paradigm to evaluate the attentional demands of functional activities. Setting Participants' homes and a clinic. Participants Twenty subjects with idiopathic PD and 10 age-, sex-, and education-matched controls. Interventions Subjects performed a simple walking task, a dual-motor task, a dual-cognitive task, and a multiple task, all of which were real-world activities. Main outcome measures Walking speed, mean step length, and step frequency were compared across different tasks for each subject. A battery of clinical outcome measures hypothesized to compete for attention were also conducted: cognition (Hayling and Brixton tests), anxiety and depression (Hospital Anxiety and Depression test), fatigue (Multidimensional Fatigue Inventory), balance (Berg Balance Scale), and disease severity (Hoehn and Yahr score). Results PD subjects walked at a significantly slower speed (26.5%, P P P =.022; P P =.022; P =.001) in PD subjects. Cognitive function, depression, physical fatigue, and balance were significantly related to walking speed for the functional tasks. Multiple regression analysis showed that the Brixton test, physical fatigue, and depression accounted for up to 39% of the variation in walking speed during functional tasks in PD and control subjects and balance accounted for 54% of variance for walking in PD subjects. Conclusions Competition for attention through additional activities, decreased executive function, depression, fatigue, and impaired balance will increase difficulty in walking for PD subjects. Evaluation of performance during complex functional activities in an appropriate environment should be a focus of therapeutic assessment. Furthermore, functional performance may be influenced by several other symptoms that should also be considered.

Background Although visuospatial deficits have been linked with freezing of gait (FOG) in Parkinson's disease (PD), the specific effects of dorsal and ventral visual pathway dysfunction on FOG is not well understood. Method We assessed visuospatial function in FOG using an angle discrimination test (dorsal visual pathway bias) and overlapping figure test (ventral visual pathway bias), and recorded overall response time, mean fixation duration and dwell time. Covariate analysis was conducted controlling for disease duration, motor severity, contrast sensitivity and attention with Bonferroni adjustments for multiple comparisons. Results Twenty seven people with FOG, 27 people without FOG and 24 controls were assessed. Average fixation duration during angle discrimination distinguished freezing status: [ F (1, 43) = 4.77 p Conclusion Results indicate a preferential dysfunction of dorsal occipito-parietal pathways in FOG, independent of disease severity, attentional deficit, and contrast sensitivity.

The Vitaport Activity Monitor (VAM) is an ambulatory monitoring device that uses accelerometer signals to assess the quality and quantity of walking and mobility related activities in home and community. The objective of this study was to investigate the concurrent validity of the VAM and GAITRite((R)) to measure gait speed, step length and step frequency during a test of functional gait that included single, dual and multiple task components for 12 people with Parkinsons Disease (PD) and 11 comparisons participating. For PD participants, ICCs were excellent for all gait variables (ICC (2, 2)=0.92-0.99, p< or =0.0001). For control participants, ICCs were good to excellent for all gait variables (ICC (2, 2)=0.74-0.94, p< or =0.05). Mean score differences between the two instruments were greatest for step frequency for both PD and comparisons. The VAM is useful for objective gait measurement in the home and community.

Introduction: Instrumented gait analysis is traditionally carried out in standardised indoor conditions [1], which may not reflect free natural walking. Wearable sensors can be used to record data in free walking conditions to improve and reinforce the interpretation of data acquired in laboratory conditions. Using plantar pressure insoles and magneto-inertial sensors, this study aimed to determine if straight walking temporal parameters are influenced by the environment (indoor or outdoor) and by the type of walking experiment (controlled or free), in a group of healthy volunteers. Methods: Ten healthy participants were instructed to walk at self-selected pace in a 25-m long straight path (8 times), both indoor and outdoor. Then, they were asked to walk freely without restrictions both indoor along the university corridors (∼5 min) and outdoor, in the city centre (∼15 min). A portable plantar pressure system (F-Scan, Tekscan) and inertial sensors (Opal, Apdm) were used to record data. Straight walking intervals during free walking were isolated for comparison applying a Haar wavelet transform to the quaternion output of the lumbar (L5) inertial sensor, to identify changes in walking direction. Mean, standard deviation (SD) and coefficient of variation (CV) were computed for the temporal parameters [2]. Hundred-fifty steps were isolated per each walking condition and differences were investigated using two-way (environment and type of walking) repeated measures ANOVA (post-hoc pairwise comparison with p = 0.01 and Bonferroni correction). Results: The results are summarised in Table 1. There was a significant main effect of environment for swing time (p = 0.004), step time (p = 0.010) and stride time (p = 0.002), with all three parameters being smaller during outdoor walking. There was a significant main effect of type of walking on step (p = 0.007) and stride (p = 0.008) time and step cadence (p = 0.004). No interaction effects were observed.