Is White Matter Hyperintensity Burden Associated with Cognitive and Motor Impairment in Patients with Parkinson's Disease? A Systematic Review and Meta-Analysis

White matter damage quantified as white matter hyperintensities (WMH) may aggravate cognitive and motor impairments, but whether and how WMH burden impacts these problems in Parkinson's disease (PD) is not fully understood. This study aimed to examine the association between WMH and cognitive and motor performance in PD through a systematic review and meta-analysis. We compared the WMH burden across the cognitive spectrum (cognitively normal, mild cognitive impairment, dementia) in PD including controls. Motor signs were compared in PD with low/negative and high/positive WMH burden. We compared baseline WMH burden of PD who did and did not convert to MCI or dementia. MEDLINE and EMBASE databases were used to conduct the literature search resulting in 50 studies included for data extraction. Increased WMH burden was found in individuals with PD compared with individuals without PD (i.e. control) and across the cognitive spectrum in PD (i.e. PD, PD-MCI, PDD). Individuals with PD with high/positive WMH burden had worse global cognition, executive function, and attention. Similarly, PD with high/positive WMH presented worse motor signs compared with individuals presenting low/negative WMH burden. Only three longitudinal studies were retrieved from our search and they showed that PD who converted to MCI or dementia, did not have significantly higher WMH burden at baseline, although no data was provided on WMH burden changes during the follow up. We conclude, based on cross-sectional studies, that WMH burden appears to increase with PD worse cognitive and motor status in PD.

Gray matter loss relates to dual task gait in Lewy body disorders and aging

BACKGROUND

Within the spectrum of Lewy body disorders (LBD), both Parkinson's disease (PD) and dementia with Lewy bodies (DLB) are characterized by gait and balance disturbances, which become more prominent under dual-task (DT) conditions. The brain substrates underlying DT gait variations, however, remain poorly understood in LBD.

OBJECTIVE

To investigate the relationship between gray matter volume loss and DT gait variations in LBD.

METHODS

Seventy-nine participants including cognitively unimpaired PD, PD with mild cognitive impairment, PD with dementia (PDD), or DLB and 20 cognitively unimpaired controls were examined across a multi-site study. PDD and DLB were grouped together for analyses. Differences in gait speed between single and DT conditions were quantified by dual task cost (DTC). Cortical, subcortical, ventricle, and cerebellum brain volumes were obtained using FreeSurfer. Linear regression models were used to examine the relationship between gray matter volumes and DTC.

RESULTS

Smaller amygdala and total cortical volumes, and larger ventricle volumes were associated with a higher DTC across LBD and cognitively unimpaired controls. No statistically significant interaction between group and brain volumes were found. Adding cognitive and motor covariates or white matter hyperintensity volumes separately to the models did not affect brain volume and DTC associations.

CONCLUSION

Gray matter volume loss is associated with worse DT gait performance compared to single task gait, across cognitively unimpaired controls through and the LBD spectrum. Impairment in DT gait performance may be driven by age-related cortical neurodegeneration.

A Metabolomics Analysis of a Novel Phenotype of Older Adults at Higher Risk of Dementia

BACKGROUND

Older adults presenting with dual-decline in cognition and walking speed face a 6-fold higher risk for dementia compared with those showing no decline. We hypothesized that the metabolomics profile of dual-decliners would be unique even before they show signs of decline in cognition and gait speed.

OBJECTIVE

The objective of this study was to determine if plasma metabolomics signatures can discriminate dual-decliners from no decliners, purely cognitive decliners, and purely motor decliners prior to decline.

METHODS

A retrospective cross-sectional study using baseline plasma for untargeted metabolomics analyses to investigate early signals of later dual-decline status in study participants (n = 76) with convenient sampling. Dual-decline was operationalized as decline in gait speed (>10 cm/s) and cognition (>2 points decline in Montreal Cognitive Assessment score) on at least two consecutive 6-monthly assessments. The participants' decliner status was evaluated 3 years after the blood sample was collected. Pair-wise comparison of detected compounds was completed using principal components and hierarchical clustering analyses.

RESULTS

Analyses did not detect any cluster separation in untargeted metabolomes across baseline groups. However, follow-up analyses of specific molecules detected 4 compounds (17-Hydroxy-12-(hydroxymethyl)-10-oxo-8 oxapentacyclomethyl hexopyranoside, Fleroxacin, Oleic acid, and 5xi-11,12-Dihydroxyabieta-8(14),9(11),12-trien-20-oic acid) were at significantly higher concentration among the dual-decliners compared to non-decliners. The pure cognitive decliner group had significantly lower concentration of six compounds (1,3-nonanediol acetate, 4-(2-carboxyethyl)-2-methoxyphenyl beta-D-glucopyranosiduronic acid, oleic acid, 2E-3-[4-(sulfo-oxy)phenyl] acrylic acid, palmitelaidic acid, and myristoleic acid) compared to the non-decliner group.

CONCLUSIONS

The unique metabolomics profile of dual-decliners warrants follow-up metabolomics analysis. Results may point to modifiable pathways.

Effects of Exercise Alone or Combined With Cognitive Training and Vitamin D Supplementation to Improve Cognition in Adults With Mild Cognitive Impairment: A Randomized Clinical Trial

Importance

Exercise, cognitive training, and vitamin D may enhance cognition in older adults with mild cognitive impairment (MCI).

Objective

To determine whether aerobic-resistance exercises would improve cognition relative to an active control and if a multidomain intervention including exercises, computerized cognitive training, and vitamin D supplementation would show greater improvements than exercise alone.

Design, Setting, and Participants

This randomized clinical trial (the SYNERGIC Study) was a multisite, double-masked, fractional factorial trial that evaluated the effects of aerobic-resistance exercise, computerized cognitive training, and vitamin D on cognition. Eligible participants were between ages 65 and 84 years with MCI enrolled from September 19, 2016, to April 7, 2020. Data were analyzed from February 2021 to December 2022.

Interventions

Participants were randomized to 5 study arms and treated for 20 weeks: arm 1 (multidomain intervention with exercise, cognitive training, and vitamin D), arm 2 (exercise, cognitive training, and placebo vitamin D), arm 3 (exercise, sham cognitive training, and vitamin D), arm 4 (exercise, sham cognitive training, and placebo vitamin D), and arm 5 (control group with balance-toning exercise, sham cognitive training, and placebo vitamin D). The vitamin D regimen was a 10 000 IU dose 3 times weekly.

Main Outcomes and Measures

Primary outcomes were changes in ADAS-Cog-13 and Plus variant at 6 months.

Results

Among 175 randomized participants (mean [SD] age, 73.1 [6.6] years; 86 [49.1%] women), 144 (82%) completed the intervention and 133 (76%) completed the follow-up (month 12). At 6 months, all active arms (ie, arms 1 through 4) with aerobic-resistance exercise regardless of the addition of cognitive training or vitamin D, improved ADAS-Cog-13 when compared with control (mean difference, -1.79 points; 95% CI, -3.27 to -0.31 points; P = .02; d = 0.64). Compared with exercise alone (arms 3 and 4), exercise and cognitive training (arms 1 and 2) improved the ADAS-Cog-13 (mean difference, -1.45 points; 95% CI, -2.70 to -0.21 points; P = .02; d = 0.39). No significant improvement was found with vitamin D. Finally, the multidomain intervention (arm 1) improved the ADAS-Cog-13 score significantly compared with control (mean difference, -2.64 points; 95% CI, -4.42 to -0.80 points; P = .005; d = 0.71). Changes in ADAS-Cog-Plus were not significant.

Conclusions and Relevance

In this clinical trial, older adults with MCI receiving aerobic-resistance exercises with sequential computerized cognitive training significantly improved cognition, although some results were inconsistent. Vitamin D supplementation had no effect. Our findings suggest that this multidomain intervention may improve cognition and potentially delay dementia onset in MCI.

Trial Registration

ClinicalTrials.gov Identifier: NCT02808676.

Association of Dual-Task Gait Cost and White Matter Hyperintensity Burden Poststroke: Results From the ONDRI

BACKGROUND

Acute change in gait speed while performing a mental task [dual-task gait cost (DTC)], and hyperintensity magnetic resonance imaging signals in white matter are both important disability predictors in older individuals with history of stroke (poststroke). It is still unclear, however, whether DTC is associated with overall hyperintensity volume from specific major brain regions in poststroke.

METHODS

This is a cohort study with a total of 123 older (69 ± 7 years of age) participants with history of stroke were included from the Ontario Neurodegenerative Disease Research Initiative. Participants were clinically assessed and had gait performance assessed under single- and dual-task conditions. Structural neuroimaging data were analyzed to measure both, white matter hyperintensity (WMH) and normal appearing volumes. Percentage of WMH volume in frontal, parietal, occipital, and temporal lobes as well as subcortical hyperintensities in basal ganglia + thalamus were the main outcomes. Multivariate models investigated associations between DTC and hyperintensity volumes, adjusted for age, sex, years of education, global cognition, vascular risk factors, APOE4 genotype, residual sensorimotor symptoms from previous stroke and brain volume.

RESULTS

There was a significant positive global linear association between DTC and hyperintensity burden (adjusted Wilks' λ = .87, P = .01). Amongst all WMH volumes, hyperintensity burden from basal ganglia + thalamus provided the most significant contribution to the global association (adjusted β = .008, η² = .03; P = .04), independently of brain atrophy.

CONCLUSIONS

In poststroke, increased DTC may be an indicator of larger white matter damages, specifically in subcortical regions, which can potentially affect the overall cognitive processing and decrease gait automaticity by increasing the cortical control over patients' locomotion.

Combining exercise with cognitive training and vitamin D3 to improve functional brain connectivity (FBC) in older adults with mild cognitive impairment (MCI). Results from the SYNERGIC trial

Changes in functional brain connectivity (FBC) may indicate how lifestyle modifications can prevent the progression to dementia; FBC identifies areas that are spatially separate but temporally synchronized in their activation and is altered in those with mild cognitive impairment (MCI), a prodromal state between healthy cognitive aging and dementia. Participants with MCI were randomly assigned to one of five study arms. Three times per week for 20-weeks, participants performed 30-min of (control) cognitive training, followed by 60-min of (control) physical exercise. Additionally, a vitamin D₃ (10,000 IU/pill) or a placebo capsule was ingested three times per week for 20-weeks. Using the CONN toolbox, we measured FBC change (Post-Pre) across four statistical models that collapsed for and/or included some or all study arms. We conducted Pearson correlations between FBC change and changes in physical and cognitive functioning. Our sample included 120 participants (mean age: 73.89 ± 6.50). Compared to the pure control, physical exercise (model one; p-False Discovery Rate (FDR) < 0.01 & < 0.05) with cognitive training (model two; p-FDR =  < 0.001), and all three interventions combined (model four; p-FDR =  < 0.01) demonstrated an increase in FBC between regions of the Default-Mode Network (i.e., hippocampus and angular gyrus). After controlling for false discovery rate, there were no significant correlations between change in connectivity and change in cognitive or physical function. Physical exercise alone appears to be as efficacious as combined interventional strategies in altering FBC, but implications for behavioral outcomes remain unclear.

Brain Structural Correlates of Obstacle Negotiation in Mild Cognitive Impairment: Results from the Gait and Brain Study

INTRODUCTION

Mild cognitive impairment (MCI) affects obstacle negotiation capabilities, potentially increasing the risk of falls in older adults. However, it is unclear whether smaller brain volumes typically observed in older individuals with MCI are related to the observed hazardous obstacle negotiation in this population.

METHODS

A total of 93 participants (71.9 ± 5.36 years of age; MCI = 53/control = 40) from the Gait and Brain Study were analyzed. Gray matter (GM) volumes from the frontal, temporal, and parietal lobes were entered in the analysis. Gait performance was recorded using a 6-m electronic walkway during two cognitive load conditions while approaching and stepping over an obstacle: (1) single-task and (2) while counting backwards by 1s from 100 (dual-task). Anticipatory adjustments in gait performance to cross an "ad hoc" obstacle were electronically measured during pre-crossing phases: early (3 steps before the late phase) and late (3 steps before obstacle). Association between the percentage of change in average gait speed and step length from early to late (i.e., anticipatory adjustments) and GM volumes was investigated using multivariate models adjusted for potential confounders.

RESULTS

Anticipatory adjustments in gait speed (Wilks' lambda: 0.35; Eta2: 0.64; p = 0.01) and step length (Wilks' lambda: 0.33; Eta2: 0.66; p = 0.01) during dual-task conditions were globally associated with GM volumes in MCI. Individuals with MCI with smaller GM volumes in the left inferior frontal gyrus, left hippocampus, right hippocampus, and right entorhinal cortex made significantly fewer anticipatory gait adjustments prior to crossing the obstacle.

CONCLUSION

Frontotemporal atrophy may affect obstacle negotiation capabilities potentially increasing the risk of falls in MCI.

Dual-task gait and white matter hyperintensities in Lewy body diseases: An exploratory analysis

Background

Parkinson’s disease (PD) and dementia with Lewy bodies (DLB) are part of a spectrum of Lewy body disorders, who exhibit a range of cognitive and gait impairments. Cognitive-motor interactions can be examined by performing a cognitive task while walking and quantified by a dual task cost (DTC). White matter hyperintensities (WMH) on magnetic resonance imaging have also been associated with both gait and cognition. Our goal was to examine the relationship between DTC and WMH in the Lewy body spectrum, hypothesizing DTC would be associated with increased WMH volume.

Methods

Seventy-eight participants with PD, PD with mild cognitive impairment (PD-MCI), PD with dementia or DLB (PDD/DLB), and 20 cognitively unimpaired participants were examined in a multi-site study. Gait was measured on an electronic walkway during usual gait, counting backward, animal fluency, and subtracting sevens. WMH were quantified from magnetic resonance imaging using an automated pipeline and visual rating. A median split based on DTC was performed. Models included age as well as measures of global cognition and cardiovascular risk.

Results

Compared to cognitively unimpaired participants, usual gait speed was lower and DTC was higher in PD-MCI and PDD/DLB. Low DTC participants had higher usual gait speed. WMH burden was greater in high counting DTC participants. Frontal WMH burden remained significant after adjusting for age, cardiovascular risk and global cognition.

Conclusion

Increased DTC was associated with higher frontal WMH burden in Lewy body disorders after adjusting for age, cardiovascular risk, and global cognition. Higher DTC was associated with age.

White matter hyperintensity burden predicts cognitive but not motor decline in Parkinson's disease: results from the Ontario Neurodegenerative Diseases Research Initiative

BACKGROUND AND PURPOSE

The pathophysiology of Parkinson's disease (PD) negatively affects brain network connectivity, and in the presence of brain white matter hyperintensities (WMHs) cognitive and motor impairments seem to be aggravated. However, the role of WMHs in predicting accelerating symptom worsening remains controversial. The objective was to investigate whether location and segmental brain WMH burden at baseline predict cognitive and motor declines in PD after 2 years.

METHODS

Ninety-eight older adults followed longitudinally from Ontario Neurodegenerative Diseases Research Initiative with PD of 3-8 years in duration were included. Percentages of WMH volumes at baseline were calculated by location (deep and periventricular) and by brain region (frontal, temporal, parietal, occipital lobes and basal ganglia + thalamus). Cognitive and motor changes were assessed from baseline to 2-year follow-up. Specifically, global cognition, attention, executive function, memory, visuospatial abilities and language were assessed as were motor symptoms evaluated using the Movement Disorder Society Unified Parkinson's Disease Rating Scale Part III, spatial-temporal gait variables, Freezing of Gait Questionnaire and Activities Specific Balance Confidence Scale.

RESULTS

Regression analysis adjusted for potential confounders showed that total and periventricular WMHs at baseline predicted decline in global cognition (p < 0.05). Also, total WMH burden predicted the decline of executive function (p < 0.05). Occipital WMH volumes also predicted decline in global cognition, visuomotor attention and visuospatial memory declines (p < 0.05). WMH volumes at baseline did not predict motor decline.

CONCLUSION

White matter hyperintensity burden at baseline predicted cognitive but not motor decline in early to mid-stage PD. The motor decline observed after 2 years in these older adults with PD is probably related to the primary neurodegenerative process than comorbid white matter pathology.

Localized White Matter Tract Integrity Measured by Diffusion Tensor Imaging Is Altered in People with Mild Cognitive Impairment and Associated with Dual-Task and Single-Task Gait Speed

BACKGROUND

Altered white matter (WM) tract integrity may contribute to mild cognitive impairment (MCI) and gait abnormalities.

OBJECTIVE

The purpose of this study was to determine whether diffusion tensor imaging (DTI) metrics were altered in specific portions of WM tracts in people with MCI and to determine whether gait speed variations were associated with the specific DTI metric changes.

METHODS

DTI was acquired in 44 people with MCI and 40 cognitively normal elderly controls (CNCs). Fractional anisotropy (FA) and radial diffusivity (RD) were measured along 18 major brain WM tracts using probabilistic tractography. The average FA and RD along the tracts were compared between the groups using MANCOVA and post-hoc tests. The tracts with FA or RD differences between the groups were examined using an along-tract exploratory analysis to identify locations that differed between the groups. Associations between FA and RD in whole tracts and in the segments of the tracts that differed between the groups and usual/dual-task gait velocities and gross cognition were examined.

RESULTS

Lower FA and higher RD was observed in right cingulum-cingulate gyrus endings (rh.ccg) of the MCI group compared to the CNC group. These changes were localized to the posterior portions of the rh.ccg and correlated with gait velocities.

CONCLUSION

Lower FA and higher RD in the posterior portion of the rh.ccg adjacent to the posterior cingulate suggests decreased microstructural integrity in the MCI group. The correlation of these metrics with gait velocities suggests an important role for this tract in maintaining normal cognitive-motor function.

Characteristics of the Ontario Neurodegenerative Disease Research Initiative cohort

INTRODUCTION

Understanding synergies between neurodegenerative and cerebrovascular pathologies that modify dementia presentation represents an important knowledge gap.

METHODS

This multi-site, longitudinal, observational cohort study recruited participants across prevalent neurodegenerative diseases and cerebrovascular disease and assessed participants comprehensively across modalities. We describe univariate and multivariate baseline features of the cohort and summarize recruitment, data collection, and curation processes.

RESULTS

We enrolled 520 participants across five neurodegenerative and cerebrovascular diseases. Median age was 69 years, median Montreal Cognitive Assessment score was 25, median independence in activities of daily living was 100% for basic and 93% for instrumental activities. Spousal study partners predominated; participants were often male, White, and more educated. Milder disease stages predominated, yet cohorts reflect clinical presentation.

DISCUSSION

Data will be shared with the global scientific community. Within-disease and disease-agnostic approaches are expected to identify markers of severity, progression, and therapy targets. Sampling characteristics also provide guidance for future study design.

World guidelines for falls prevention and management for older adults: a global initiative

BACKGROUND

falls and fall-related injuries are common in older adults, have negative effects on functional independence and quality of life and are associated with increased morbidity, mortality and health related costs. Current guidelines are inconsistent, with no up-to-date, globally applicable ones present.

OBJECTIVES

to create a set of evidence- and expert consensus-based falls prevention and management recommendations applicable to older adults for use by healthcare and other professionals that consider: (i) a person-centred approach that includes the perspectives of older adults with lived experience, caregivers and other stakeholders; (ii) gaps in previous guidelines; (iii) recent developments in e-health and (iv) implementation across locations with limited access to resources such as low- and middle-income countries.

METHODS

a steering committee and a worldwide multidisciplinary group of experts and stakeholders, including older adults, were assembled. Geriatrics and gerontological societies were represented. Using a modified Delphi process, recommendations from 11 topic-specific working groups (WGs), 10 ad-hoc WGs and a WG dealing with the perspectives of older adults were reviewed and refined. The final recommendations were determined by voting.

RECOMMENDATIONS

all older adults should be advised on falls prevention and physical activity. Opportunistic case finding for falls risk is recommended for community-dwelling older adults. Those considered at high risk should be offered a comprehensive multifactorial falls risk assessment with a view to co-design and implement personalised multidomain interventions. Other recommendations cover details of assessment and intervention components and combinations, and recommendations for specific settings and populations.

CONCLUSIONS

the core set of recommendations provided will require flexible implementation strategies that consider both local context and resources.

Evaluation of Clinical Practice Guidelines on Fall Prevention and Management for Older Adults: A Systematic Review

Importance

With the global population aging, falls and fall-related injuries are ubiquitous, and several clinical practice guidelines for falls prevention and management for individuals 60 years or older have been developed. A systematic evaluation of the recommendations and agreement level is lacking.

Objectives

To perform a systematic review of clinical practice guidelines for falls prevention and management for adults 60 years or older in all settings (eg, community, acute care, and nursing homes), evaluate agreement in recommendations, and identify potential gaps.

Evidence Review

A systematic review following Preferred Reporting Items for Systematic Reviews and Meta-analyses statement methods for clinical practice guidelines on fall prevention and management for older adults was conducted (updated July 1, 2021) using MEDLINE, PubMed, PsycINFO, Embase, CINAHL, the Cochrane Library, PEDro, and Epistemonikos databases. Medical Subject Headings search terms were related to falls, clinical practice guidelines, management and prevention, and older adults, with no restrictions on date, language, or setting for inclusion. Three independent reviewers selected records for full-text examination if they followed evidence- and consensus-based processes and assessed the quality of the guidelines using Appraisal of Guidelines for Research & Evaluation II (AGREE-II) criteria. The strength of the recommendations was evaluated using Grades of Recommendation, Assessment, Development, and Evaluation scores, and agreement across topic areas was assessed using the Fleiss κ statistic.

Findings

Of 11 414 records identified, 159 were fully reviewed and assessed for eligibility, and 15 were included. All 15 selected guidelines had high-quality AGREE-II total scores (mean [SD], 80.1% [5.6%]), although individual quality domain scores for clinical applicability (mean [SD], 63.4% [11.4%]) and stakeholder (clinicians, patients, or caregivers) involvement (mean [SD], 76.3% [9.0%]) were lower. A total of 198 recommendations covering 16 topic areas in 15 guidelines were identified after screening 4767 abstracts that proceeded to 159 full texts. Most (≥11) guidelines strongly recommended performing risk stratification, assessment tests for gait and balance, fracture and osteoporosis management, multifactorial interventions, medication review, exercise promotion, environment modification, vision and footwear correction, referral to physiotherapy, and cardiovascular interventions. The strengths of the recommendations were inconsistent for vitamin D supplementation, addressing cognitive factors, and falls prevention education. Recommendations on use of hip protectors and digital technology or wearables were often missing. None of the examined guidelines included a patient or caregiver panel in their deliberations.

Conclusions and Relevance

This systematic review found that current clinical practice guidelines on fall prevention and management for older adults showed a high degree of agreement in several areas in which strong recommendations were made, whereas other topic areas did not achieve this level of consensus or coverage. Future guidelines should address clinical applicability of their recommendations and include perspectives of patients and other stakeholders.

Long-term living in unfavorable socioeconomic conditions impairs late-life gait performance

BACKGROUND

Low socioeconomic status has been associated with individual health-related problems; however, no study has specifically investigated the impact of socioeconomic disparities on gait performance using an index that considers the population aggregation, as the Human Development Index (HDI). Thus, the aim of the present study was to assess gait parameters of older people living in cities with differences in socioeconomic conditions, identified by HDI.

METHODS

Cross-sectional design study conducted with a sample of 233 older people from two Brazilians regions: Coari, state of Amazonas, Brazil (n= 124, low-HDI-Bra) and Ribeirão Preto, state of São Paulo, Brazil (n= 109, very high-HDI-Bra). The gait performance was assessed by an electronic walkway, and the interest variables were gait speed, cadence, stride time, step length and stride width.

RESULTS

Low-HDI-Bra group presented worse gait performance as identified by slower gait speed (p = < .001), slower cadence (p = < .001), higher stride time (p = < .001), shorter step length (p = < .001), compared with the very high-HDI-Bra group. There was a positive association between HDI, and gait spend, cadence and step length, and there was a negative association between HDI and stride time and stride width.

CONCLUSIONS

Long-term exposure to socioeconomic inequalities found in low HDI cities may impair gait performance in late life. Such information may be relevant to create public politics that use the gait parameter based on the region where the people live.

Association of age-related cognitive and obstacle avoidance performances

An association between cognitive impairment and tripping over obstacles during locomotion in older adults has been suggested. However, owing to its memory-guided movement, whether this is more pronounced in the trailing limb is poorly known. We examined age-related changes in stepping over, focusing on trailing limb movements, and their association with cognitive performance. Age-related changes in obstacle avoidance were examined by comparing the foot kinematics of 105 older and 103 younger adults when stepping over an obstacle. The difference in the clearance between the leading and trailing limbs (Δ clearance) was calculated to determine the degree of decrement in the clearance of the trailing limb. A cognitive test battery was used to evaluate cognitive function among older adults to assess their association with Δ clearance. Older adults showed a significantly lower clearance of the trailing limb than young adults, resulting in greater Δ clearance. Significant correlations were observed between greater Δ clearance and scores on the Montreal Cognitive Assessment and immediate recall of the Wechsler Memory Scale-Revised Logical Memory test. Therefore, memory functions may contribute to the control of trailing limb movements, which can secure a safety margin to avoid stumbling over an obstacle during obstacle avoidance locomotion.

The effect of physical exercise on functional brain network connectivity in older adults with and without cognitive impairment. A systematic review

INTRODUCTION

Neurodegeneration is a biproduct of aging that results in concomitant cognitive decline. Physical exercise is an emerging intervention to improve brain health. The underlying neural mechanisms linking exercise to neurodegeneration, however, are unclear. Functional brain network connectivity (FBNC) refers to neural regions that are anatomically separate but temporally synched in functional signalling. FBNC can be measured using functional Magnetic Resonance Imaging (fMRI) and is affected by neurodegeneration.

METHODS

We conducted a systematic review using PubMed and EMBASE to assess the effect of physical exercise on FBNC in older adults with and without cognitive impairment.

RESULTS

Our search yielded 1474 articles; after exclusion, 13 were included in the final review, 8 of which focused on cognitively healthy older adults. 10 studies demonstrated an increase in FBNC post-exercise intervention, while 11 studies showed improvements in secondary outcomes (cognitive and/or physical performance). One study showed significant correlations between FBNC and cognitive performance measures that significantly improved post-intervention.

DISCUSSION

We found evidence that physical exercise increases FBNC. When assessing the association between FBNC with physical and cognitive functioning, careful consideration must be given to variability in exercise parameters, neural regions of interest and networks examined, and heterogeneity in methodological approaches.

Potentially modifiable risk factors for slow gait in community-dwelling older adults: A systematic review

PURPOSE

Slow gait speed in older adults is associated with increased risk for falls and fractures, functional dependence, multimorbidity, and even mortality. The risk of these adverse outcomes can be reduced by intervening on potentially modifiable risk factors. The purpose of this systematic review was to identify potentially modifiable risk factors associated with slow gait speed and clinically meaningful gait speed decline in older community-dwelling adults.

METHODS

Literature searches were conducted in MEDLINE, EMBASE, and CINAHL, Google Scholar, and in the bibliographies of retrieved articles.

RESULTS

Forty studies met the inclusion criteria for qualitative review. Study designs were cross-sectional and longitudinal. Operational definitions of 'slow gait' and 'meaningful gait speed decline' were variable and based on sample distributions (e.g. quartiles), external criteria (e.g. < 0.8 m/s), and dynamic changes over time (e.g. ≥ 0.05 m/s decline per year). Twenty-six potentially modifiable risk factors were assessed in at least two studies. The risk factors most commonly investigated and that showed significant associations with slow gait and/or meaningful gait speed decline include physical activity, education, body mass index-obesity, pain, and depression/depressive symptoms.

CONCLUSION

Our results suggest that there are modifiable targets to maintain gait speed that are amenable to potential treatment.

Gait variability across neurodegenerative and cognitive disorders: Results from the Canadian Consortium of Neurodegeneration in Aging (CCNA) and the Gait and Brain Study

Introduction

Gait impairment is common in neurodegenerative disorders. Specifically, gait variability—the stride‐to‐stride fluctuations in distance and time—has been associated with neurodegeneration and cognitive impairment. However, quantitative comparisons of gait impairments across the cognitive spectrum of dementias have not been systematically investigated.

Methods

Older adults (N = 500) with subjective cognitive impairment, Parkinson disease (PD), mild cognitive impairment (MCI), PD‐MCI, Alzheimer's disease (AD), PD‐dementia, Lewy body dementia, and frontotemporal dementia, as well cognitive normal controls, who were assessed for their gait and cognitive performance.

Results

Factor analyses grouped 11 quantitative gait parameters and identified four independent gait domains: rhythm, pace, variability, and postural control, for group comparisons and classification analysis. Among these domains, only high gait variability was associated with lower cognitive performance and accurately discriminated AD from other neurodegenerative and cognitive conditions.

Discussion

Our findings indicate that high gait variability is a marker of cognitive‐cortical dysfunction, which can help to identify Alzheimer's disease dementia.

Dual-Task Gait Cost and Frontal Lobe Integrity in Poststroke: Results From ONDRI

Dual-task gait performance is a marker of motor-cognitive interactions modulated by the frontal lobes. After a stroke, gait disturbances are more evident, particularly when concurrently completing a mental task and walking, an effect called high dual-task cost (DTC). Following a stroke, the potential association of high-DTC, integrity of the frontal lobes and cognitive functioning is unclear. This study screened 161 participants with stroke history from the Ontario Neurodegenerative Disease Research Initiative (ONDRI)-cerebrovascular disease cohort (69.2±7.41 years of age; 31.7% women). Individuals scoring zero in the National Institute of Health Stroke Scale were analyzed (n=102). DTC was the percentage change in gait speed from the single to dual-task condition. Standardized normal-appearing white matter (NAWM) and grey matter (NAGM) volumes from superior, middle and inferior frontal lobe were compared between DTC quartiles (adjusted for age, sex, and education) using a multivariate model (MANOVA), with total frontal lobe volume as a covariate. Another model compared group performance across 5 adjusted cognitive domains (attention, memory, language, visuospatial performance, and executive functioning). Univariate tests revealed that NAWM volume in the superior frontal lobe (F=4.50; p=0.005; partial eta-squared=0.122) was significantly different across DTC quartiles. Contrast tests suggested that the first quartile had larger NAWM than the second and fourth. DTC quartiles also showed differences in attention (F=2.93; p=0.03; partial eta-squared=0.083) and contrast tests indicated that the first quartile performed significantly better than second and fourth. DTC poststroke may be a proxy for structural integrity of superior frontal lobe regions and attention.

Dual Decline in Gait and Cognition Is Associated With Future Dementia: Evidence for a Phenotype

BACKGROUND: The concurrent decline in gait speed and cognition are associated with future dementia. However, the clinical profile of those who present with dual-decline has not yet been described. We aimed to describe the phenotype and risk for incident dementia of individuals who present a dual-decline in comparison with non dual-decliners. METHODS: Prospective cohort of community-dwelling older adults free of dementia at baseline. We evaluated participants’ gait speed, cognition, medical status, functionality, incidence of adverse events, and dementia biannually over 7 years. Gait speed was assessed with a 6-meter electronic-walkway, and global cognition was assessed using the MoCA test. We compared characteristics between dual-decliners and non dual-decliners using t-test, Chi-square, and hierarchical regression models. We estimated incident dementia using Cox models. RESULTS: Among 144 participants (mean age 74.23 ± 6.72 years, 54% women), 17% progressed to dementia. Dual-decliners had a three-fold risk (HR: 3.12, 95%CI:1.23-7.93, p=0.017) of progression to dementia compared with non dual-decliners. Dual-decliners were significantly older with a higher prevalence of hypertension and dyslipidemia (p=0.002). Hierarchical regression models show that age and sex alone explained 3% of the variation in the dual-decliners group, while adding hypertension and dyslipidemia increased the explained variation to 8% and 10 %, respectively. The risk of becoming a dual-decliner was 4-fold if hypertension was present. CONCLUSION: Older adults with concurrent decline in gait speed and cognition represent a group at the highest risk of progression to dementia. These dual-decliners have a distinct phenotype with a higher prevalence of hypertension, a potentially treatable condition.

Dual decline in gait speed and cognition is associated with future dementia: evidence for a phenotype

BACKGROUND

concurrent declines in gait speed and cognition have been associated with future dementia. However, the clinical profile of 'dual decliners', those with concomitant decline in both gait speed and cognition, has not been yet described. We aimed to describe the phenotype and the risk for incident dementia of those who present with dual decline in comparison with non-dual decliners.

METHODS

prospective cohort of community-dwelling older adults free of dementia at baseline. We evaluated participants' gait speed, cognition, medical status, functionality, incidence of adverse events and dementia, biannually over 7 years. Gait speed was assessed with a 6-m electronic walkway and global cognition using the MoCA test. We compared characteristics between dual decliners and non-dual decliners using t-test, chi-square and hierarchical regression models. We estimated incident dementia using Cox models.

RESULTS

among 144 participants (mean age 74.23 ± 6.72 years, 54% women), 17% progressed to dementia. Dual decliners had a 3-fold risk (HR: 3.12, 95%CI: 1.23-7.93, P = 0.017) of progression to dementia compared with non-dual decliners. Dual decliners were significantly older with a higher prevalence of hypertension and dyslipidemia (P = 0.002). Hierarchical regression models show that age and sex alone explained 3% of the variation in the dual decliners group. Adding hypertension and dyslipidemia increased the explained variation by 8 and 10%, respectively. The risk of becoming a dual decliner was 4-fold higher if hypertension was present.

CONCLUSION

older adults with a concurrent decline in gait speed and cognition represent a group at the highest risk of progression to dementia. Older adults with dual decline have a distinct phenotype with a higher prevalence of hypertension, a treatable condition.

Are Cognitive Subtypes Associated with Dual-Task Gait Performance in a Clinical Setting?

BACKGROUND

Poor dual-task gait (walking while performing a cognitively demanding task) has been linked to progression to dementia in older adults with mild cognitive impairment (MCI). However, many of these findings come from research environments; gait performance across the cognitive spectrum has not previously been studied in a clinical setting.

OBJECTIVE

To examine whether patients from a memory clinic show differences in usual and dual-task gait speed and dual-task cost (DTC) based on cognitive diagnosis.

METHODS

Patients in the Aging Brain and Memory Clinic (London, ON) performed a usual gait walk and three dual-task gait walks: counting backwards by ones, naming animals, and counting backwards by seven (serial sevens) out loud. Patients were timed with a stopwatch over a six-meter path marked on the floor. One-way ANOVA was performed to evaluate associations between gait speed and DTC (%) across groups.

RESULTS

One hundred ninety-four patients with subjective cognitive impairment (SCI; n = 46), MCI (n = 77), or dementia (n = 71) were assessed. Performance in usual (p < 0.001) and dual-task gait speed (counting gait p < 0.001; naming animals p < 0.001; serial sevens p = 0.004) decreased across the spectrum of cognitive impairment. Patients with dementia had significantly higher DTC in both counting gait (p = 0.02) and naming animals (p = 0.04) conditions compared with patients with SCI and MCI, who had statistically similar DTC in all conditions.

CONCLUSION

Dual-task gait performance significantly declines across the cognitive spectrum in a clinical setting. Dual-task gait testing may be used in conjunction with traditional assessments for diagnosing cognitive impairments.

Dual-task gait speed assessments with an electronic walkway and a stopwatch in older adults. A reliability study

BACKGROUND/OBJECTIVES

Slow gait speed prospectively predicts elevated risk of adverse events such as falls, morbidity, and mortality. Additionally, gait speed under a cognitively demanding challenge (dual-task gait) predicts further cognitive decline and dementia incidence. This evidence has been mostly collected using electronic walkways; however, not all clinical set ups have an electronic walkway and comparability with simple manual dual-gait speed testing, like a stopwatch, has not yet been examined. Our main objective was to assess concurrent-validity and reliability of gait speed assessments during dual-tasking using a stopwatch and electronic walkway in older adults with mild and subjective cognitive impairment (MCI and SCI).

DESIGN

Cross-sectional, reliability study.

SETTING

Clinic based laboratory at an academic hospital in London, ON, Canada.

PARTICIPANTS

237 walk tests from 34 community-dwelling participants (mean age 71.84 SD 5.38; 21 female - 62%, 13 male - 38%) with SCI and MCI. were included from the Comprehensive Assessment of Neurodegeneration and Dementia (COMPASS-ND) study.

INTERVENTION

Each participant performed seven walk tests: three single gait walks at their normal pace, three dual-task walks (walking and counting backwards by one, by sevens, and naming animals), and one fast walk.

MEASUREMENTS

Gait speed (cm/s) for each walk was measured simultaneously with an electronic walkway (Zeno Mat®) and a handheld stopwatch (Ultrak chronometer®). Dual-task cost (DTC) was calculated for the three individual dual-task walks as [((single gait speed - dual-task gait speed) / single gait speed) ∗ 100]. Level of agreement between the two measurement methods was analyzed using Pearson correlations, paired t-tests, and Bland-Altman plots.

RESULTS

Gait speed was consistently lower when measured with the stopwatch than with the electronic walkway (mean speed difference: 10.6 cm/s ± 5.1, p < 0.001). Calculating DTC, however, yielded very similar results with both methods (mean DTC difference: 0.19 ± 1.18, p = 0.872). The higher the DTC, the closer the measurement between methods.

CONCLUSION

Assessing and calculating DTC with a stopwatch is simple, accessible and reliable. Its validity and reliability were high in this clinical sample of community older adults with SCI and MCI.

Obstacle Negotiation, Gait Variability, and Risk of Falling: Results From the "Gait and Brain Study"

BACKGROUND

Gait variability is an early fall predictor. However, it is unknown how gait variability of older adults at high risk of falls is affected by an obstacle negotiation task. We aimed to compare gait performance between older adults with significant history of falls (i.e. fallers) and nonfallers while approaching an obstacle crossing.

METHODS

A total of 137 older adults without dementia were enrolled (72.7 ± 5.1 years of age; 60.5% women) from the "Gait and Brain Study." Fallers were defined as having at least one injurious fall or at least two noninjurious falls in the previous 12 months. Participants performed gait assessments under unobstructed and obstructed conditions. During the obstructed condition, participants walked and stepped over an ad hoc obstacle set at 15% of participants' height, transversally placed on a 6-meter electronic walkway. Gait speed and step-to-step variabilities were quantified from the last six steps prior to obstacle crossing. Analysis of variance models adjusted for age, sex, fear of falling, comorbidities, and unobstructed gait were used to compare gait performance of fallers and nonfallers during an obstacle approaching.

RESULTS

In the study, 27 older adults were identified as fallers and 110 as nonfallers. Fallers had higher step time variability and step length variability when approaching an obstacle compared with nonfallers, although groups had comparable gait performance during unobstructed walking.

CONCLUSION

Gait variability of older individuals at high risk of falling is more disturbed, compared with low-risk individuals, while approaching an obstacle crossing. High gait variability prior to crossing an obstacle may be a risk factor for falls.

Mental Flexibility Influences the Association Between Poor Balance and Falls in Older People - A Secondary Analysis

Impairments of balance predispose older people to falls. Some cognitive functions, especially executive functioning have been shown to affect balance and discriminate fallers from non-fallers. Mental flexibility is a component of the executive function and comprises multiple cognitive processes that work together to adjust the course of thoughts or actions according to the changing demands of a situation without the use of explicit instructions. However, the role of mental flexibility in balance in older people remains unclear. The study aim was to examine the relationship between mental flexibility and falls in a cohort of 212 older people (80.6 ± 4.9 years; 62% female). We hypothesized that: (i) participants with impaired balance would have worse mental flexibility compared to those with good balance; and (ii) poor mental flexibility would predict falls in the sub-group with impaired balance. Balance performance was assessed by measuring postural sway while standing on a medium density foam mat with eyes open for 30 s. Mental flexibility was assessed using a computerized short-form of the Wisconsin Card Sorting Test (WCST; 64 cards) with its sub-components comprising general performance, perseveration, failure-to-maintain set and conceptual ability. Falls were measured prospectively for 12-months using monthly calendars. MANCOVA revealed that WCST performance was associated with balance [Wilks' Lambda = 0.883, F = 2.168; p = 0.013, partial eta squared ( η p 2 ) = 0.061] due primarily to reduced concept formation ability [F _(2,207) = 5.787, p = 0.004, η p 2 = 0.053]. Negative binomial regression analysis adjusting for age, education, contrast sensitivity, proprioception, inhibition, and inhibitory choice stepping reaction time (iCSRT) revealed that lower concept formation ability was predictive for falls [Incidence Rate Ratio 1.048 (95% confidence interval 1.016-1.081)]. Further, lower concept formation ability partly explained the association between balance and falls: i.e., fallers in the upper balance tertile had reduced concept formation performance whereas non-fallers had similar concept formation performance across the three balance tertiles. These findings suggest that poor mental flexibility affects the ability to maintain steady balance contributing to increased risk of falls in older people.

The utility of multivariate outlier detection techniques for data quality evaluation in large studies: an application within the ONDRI project

BACKGROUND

Large and complex studies are now routine, and quality assurance and quality control (QC) procedures ensure reliable results and conclusions. Standard procedures may comprise manual verification and double entry, but these labour-intensive methods often leave errors undetected. Outlier detection uses a data-driven approach to identify patterns exhibited by the majority of the data and highlights data points that deviate from these patterns. Univariate methods consider each variable independently, so observations that appear odd only when two or more variables are considered simultaneously remain undetected. We propose a data quality evaluation process that emphasizes the use of multivariate outlier detection for identifying errors, and show that univariate approaches alone are insufficient. Further, we establish an iterative process that uses multiple multivariate approaches, communication between teams, and visualization for other large-scale projects to follow.

METHODS

We illustrate this process with preliminary neuropsychology and gait data for the vascular cognitive impairment cohort from the Ontario Neurodegenerative Disease Research Initiative, a multi-cohort observational study that aims to characterize biomarkers within and between five neurodegenerative diseases. Each dataset was evaluated four times: with and without covariate adjustment using two validated multivariate methods - Minimum Covariance Determinant (MCD) and Candès' Robust Principal Component Analysis (RPCA) - and results were assessed in relation to two univariate methods. Outlying participants identified by multiple multivariate analyses were compiled and communicated to the data teams for verification.

RESULTS

Of 161 and 148 participants in the neuropsychology and gait data, 44 and 43 were flagged by one or both multivariate methods and errors were identified for 8 and 5 participants, respectively. MCD identified all participants with errors, while RPCA identified 6/8 and 3/5 for the neuropsychology and gait data, respectively. Both outperformed univariate approaches. Adjusting for covariates had a minor effect on the participants identified as outliers, though did affect error detection.

CONCLUSIONS

Manual QC procedures are insufficient for large studies as many errors remain undetected. In these data, the MCD outperforms the RPCA for identifying errors, and both are more successful than univariate approaches. Therefore, data-driven multivariate outlier techniques are essential tools for QC as data become more complex.

Mild Cognitive Impairment Affects Obstacle Negotiation in Older Adults: Results from “Gait and Brain Study”

Background: Older adults with Mild Cognitive Impairment (MCI) are at higher risk of falls and injuries, but the underlying mechanism is poorly understood. Inappropriate anticipatory postural adjustments to overcome balance perturbations are affected by cognitive decline. However, it is unknown whether anticipatory gait control to avoid an obstacle is affected in MCI. Objective: Using the dual-task paradigm, we aim to assess whether gait control is affected during obstacle negotiation challenges in older adults with MCI. Methods: Seventy-nine participants (mean age = 72.0 ± 2.7 years; women = 30.3%) from the “Gait and Brain Study” were included in this study (controls = 27; MCI = 52). In order to assess the anticipatory control behaviour for obstacle negotiation, a 6-m electronic walkway embedded with sensors recorded foot prints to measure gait speed and step length variability, during early (3 steps before the late phase) and late (3 steps before the obstacle) pre-crossing phases of an ad hoc obstacle, set at 15% of participant’s height. Participants walked under single- and dual-task gait (counting backwards by 1’s from 100 while walking) conditions. Three-way mixed repeated-measures analysis of variance models examined differences in gait performance between groups when transitioning between pre-crossing phases towards an obstacle during single- and dual-task conditions. Analyses were adjusted for age, sex, years of education, lower limb function, fear of falling, medical status, depressive symptoms, baseline gait speed and executive function. Results: A significant three-way interaction among groups, pre-crossing phases and task showed that participants with MCI attenuated the gait deceleration (p = 0.02) and performed fewer step length adjustments (p = 0.03) when approaching the obstacle compared with controls while dual-tasking. These interactions were attenuated when executive function performance was added as a covariate in the adjusted statistical model. Conclusion: Older adults with MCI attenuate the anticipatory gait adjustments needed to avoid an obstacle when dual-tasking. Deficits in higher-order cognitive processing may limit obstacle negotiation capabilities in MCI populations, being a potential falls risk factor.

SYNERGIC TRIAL (SYNchronizing Exercises, Remedies in Gait and Cognition) a multi-Centre randomized controlled double blind trial to improve gait and cognition in mild cognitive impairment

Background

Physical exercise, cognitive training, and vitamin D are low cost interventions that have the potential to enhance cognitive function and mobility in older adults, especially in pre-dementia states such as Mild Cognitive Impairment (MCI). Aerobic and progressive resistance exercises have benefits to cognitive performance, though evidence is somewhat inconsistent. We postulate that combined aerobic exercise (AE) and progressive resistance training (RT) (combined exercise) will have a better effect on cognition than a balance and toning control (BAT) intervention in older adults with MCI. We also expect that adding cognitive training and vitamin D supplementation to the combined exercise, as a multimodal intervention, will have synergistic efficacy.

Methods

The SYNERGIC trial (SYNchronizing Exercises, Remedies in GaIt and Cognition) is a multi-site, double-blinded, five-arm, controlled trial that assesses the potential synergic effect of combined AE and RT on cognition and mobility, with and without cognitive training and vitamin D supplementation in older adults with MCI. Two-hundred participants with MCI aged 60 to 85 years old will be randomized to one of five arms, four of which include combined exercise plus combinations of dual-task cognitive training (real vs. sham) and vitamin D supplementation (3 × 10,000 IU/wk. vs. placebo) in a quasi-factorial design, and one arm which receives all control interventions. The primary outcome measure is the ADAS-Cog (13 and plus modalities) measured at baseline and at 6 months of follow-up. Secondary outcomes include neuroimaging, neuro-cognitive performance, gait and mobility performance, and serum biomarkers of inflammation (C reactive protein and interleukin 6), neuroplasticity (brain-derived neurotropic factor), endothelial markers (vascular endothelial growth factor 1), and vitamin D serum levels.

Discussion

The SYNERGIC Trial will establish the efficacy and feasibility of a multimodal intervention to improve cognitive performance and mobility outcomes in MCI. These interventions may contribute to new approaches to stabilize and reverse cognitive-mobility decline in older individuals with MCI.

Trial Registration

Identifier: NCT02808676. https://www.clinicaltrials.gov/ct2/show/NCT02808676.

Electronic supplementary material

The online version of this article (10.1186/s12877-018-0782-7) contains supplementary material, which is available to authorized users.

Do depressive symptoms affect balance in older adults with mild cognitive impairment? Results from the "gait and brain study"

BACKGROUND

Mild cognitive impairment (MCI) and depression independently affect balance control in older adults. However, it is uncertain whether depressive symptoms would amplify balance problems in older adults with MCI.

AIM

To evaluate if the presence of significant depressive symptoms affects postural sway under somatosensory challenges in a MCI population.

METHODS

Eighty two participants (mean of 75.3 ± 6.4 years of age; 46% women) with MCI completed cognitive and balance assessments. Participants were grouped by severity of depressive symptoms using the Geriatric Depression Scale-15, as MCI with depressive symptoms (MCI-D = 14, score ≥ 5) and MCI without depressive symptoms (MCI = 68, score < 5). Postural sway area was evaluated during eyes open (EO) and eyes closed (EC) while standing on a rigid flat force plate platform, and compared across groups. Analyses were controlled for age, sex, comorbidities, anti-depressant medication use, executive function, and baseline sway.

RESULTS

MCI-D showed larger postural sway area when compared with MCI irrespective of visual feedback conditions (p = 0.03). This difference remained significant after adjusting for anti-depressant use and executive function performance. The lack of interaction between groups and visual condition was associated with group differences in postural sway during EO condition (Beta = 0.08, CI -257.5-621.9; p = 0.41) and by comparable sway increase from EO to EC in both groups.

CONCLUSION

Depressive symptoms in individuals with MCI worsened postural stability during both eyes open and eyes closed conditions independently of cognitive function. Significant depressive symptoms may affect balance in MCI populations, potentially increasing the risk of falls.

Motor Phenotype in Neurodegenerative Disorders: Gait and Balance Platform Study Design Protocol for the Ontario Neurodegenerative Research Initiative (ONDRI)

Background:

The association of cognitive and motor impairments in Alzheimer’s disease and other neurodegenerative diseases is thought to be related to damage in the common brain networks shared by cognitive and cortical motor control processes. These common brain networks play a pivotal role in selecting movements and postural synergies that meet an individual’s needs. Pathology in this “highest level” of motor control produces abnormalities of gait and posture referred to as highest-level gait disorders. Impairments in cognition and mobility, including falls, are present in almost all neurodegenerative diseases, suggesting common mechanisms that still need to be unraveled.

Objective:

To identify motor-cognitive profiles across neurodegenerative diseases in a large cohort of patients.

Methods:

Cohort study that includes up to 500 participants, followed every year for three years, across five neurodegenerative disease groups: Alzheimer’s disease/mild cognitive impairment, frontotemporal degeneration, vascular cognitive impairment, amyotrophic lateral sclerosis, and Parkinson’s disease. Gait and balance will be assessed using accelerometers and electronic walkways, evaluated at different levels of cognitive and sensory complexity, using the dual-task paradigm.

Results:

Comparison of cognitive and motor performances across neurodegenerative groups will allow the identification of motor-cognitive phenotypes through the standardized evaluation of gait and balance characteristics.

Conclusions:

As part of the Ontario Neurodegenerative Research Initiative (ONDRI), the gait and balance platform aims to identify motor-cognitive profiles across neurodegenerative diseases. Gait assessment, particularly while dual-tasking, will help dissect the cognitive and motor contribution in mobility and cognitive decline, progression to dementia syndromes, and future adverse outcomes including falls and mortality.

Disentangling perceptual judgment and online feedback deficits in Parkinson's freezing of gait

Although the underlying mechanisms of freezing of gait in Parkinson’s disease (PD) are not fully understood, impaired sensory–perceptual processing has been proposed as an important contributor to freezing episodes. The aims of this cross-sectional study were to disentangle how sensory–perceptual deficits involved in planning (prior to movement) and sensory–perceptual feedback processing (during movement execution) contribute to freezing of gait in narrow spaces. Thirteen PD participants with freezing (PD FOG), 14 PD participants without freezing (PD non-FOG), and 15 healthy individuals made a perceptual estimate of the width of the distal opening of a corridor in two conditions: parallel and narrowing walls. Gait characteristics and number of freezing episodes were then compared while participants walked in baseline (no corridor), and through parallel walls and narrowing walls corridors. Visuospatial abilities were also assessed using neuropsychological tests. PD FOG had lower scores in the copy of the pentagons (p = 0.044) and had greater error variability in the perceptual judgment task (p = 0.008) than healthy participants. Although a similar number of freezing episodes occurred in both corridor conditions, PD FOG had greater step length variability while walking through the parallel walls corridor compared to healthy (p < 0.001) and PD non-FOG (p = 0.017) participants. Regression analysis revealed that error variability in perceptual judgment predicted the percentage of time spent in double support (R² = 0.347) only in the narrowing walls condition for PD FOG. These results support the notion that sensory–perceptual deficits both prior to movement planning and during movement execution are important factors contributing to freezing of gait.

Interactions between cognitive and sensory load while planning and controlling complex gait adaptations in Parkinson's disease

Background

Recent research has argued that removal of relevant sensory information during the planning and control of simple, self-paced walking can result in increased demand on central processing resources in Parkinson’s disease (PD). However, little is known about more complex gait tasks that require planning of gait adaptations to cross over an obstacle in PD.

Methods

In order to understand the interaction between availability of visual information relevant for self-motion and cognitive load, the current study evaluated PD participants and healthy controls while walking toward and stepping over an obstacle in three visual feedback conditions: (i) no visual restrictions; (ii) vision of the obstacle and their lower limbs while in complete darkness; (iii) vision of the obstacle only while in complete darkness; as well as two conditions including a cognitive load (with a dual task versus without a dual task). Each walk trial was divided into an early and late phase to examine changes associated with planning of step adjustments when approaching the obstacle.

Results

Interactions between visual feedback and dual task conditions during the obstacle approach were not significant. Patients with PD had greater deceleration and step time variability in the late phase of the obstacle approach phase while walking in both dark conditions compared to control participants. Additionally, participants with PD had a greater number of obstacle contacts when vision of their lower limbs was not available specifically during the dual task condition. Dual task performance was worse in PD compared to healthy control participants, but notably only while walking in the dark regardless of visual feedback.

Conclusions

These results suggest that reducing visual feedback while approaching an obstacle shifts processing to somatosensory feedback to guide movement which imposes a greater demand on planning resources. These results are key to fully understanding why trips and falls occur in those with PD.

Could sensory mechanisms be a core factor that underlies freezing of gait in Parkinson's disease?

The main objective of this study was to determine how manipulating the amount of sensory information available about the body and surrounding environment influenced freezing of gait (FOG), while walking through a doorway. It was hypothesized that the more limited the sensory information, the greater the occurrence of freezing of gait. Nineteen patients with Parkinsoǹs disease who experience freezing of gait (PD-FOG) walked through a doorway or into open space in complete darkness. The three doorway conditions included: (i) FRAME (DARK)--walking through the remembered door frame; (ii) FRAME--walking through the door with the door frame illuminated; (iii) FRAME+BODY--walking through the door (both the door and the limbs illuminated). Additionally, two conditions of walking away from the doorway included: (iv) NO FRAME (DARK)--walking into open space; (v) NO FRAME+BODY--walking into open space with the limbs illuminated, to evaluate whether perception (or fear) of the doorway might account for FOG behaviour. Key outcome measures included: the number of freezing of gait episodes recorded, total duration of freezing of gait, and the percentage of time spent frozen. Significantly more freezing of gait episodes occurred when participants walked toward the doorway in complete darkness compared to walking into open space (p<0.05). Similar to previous studies, velocity (p<0.001) and step length (p<0.0001) significantly decreased when walking through the door in complete darkness, compared to all other conditions. Significant increases in step width variability were also identified but only when walking into open space (p<0.005). These results support the notion that sensory deficits may have a profound impact on freezing of gait that need to be carefully considered.

Effects of obstacle height on obstacle crossing in mild Parkinson's disease

The aim of this study was to compare the locomotor behavior of people with Parkinson's disease (PD) and healthy older adults during obstacle negotiation, both in the approaching and crossing phases. Twelve people with idiopathic PD, with mild to moderate disease, and 12 healthy individuals (CG) walked across an 8m pathway for three obstacle conditions: no obstacle, low obstacle and high obstacle. Each performed five trials for each obstacle condition. Performance was more disturbed for the high obstacle than the low obstacle. During the approach phase, people with PD demonstrated shorter stride length (F(1,22)=8.55, P=0.008) and greater stride duration (F(1,22)=7.371, P=0.013) than controls. Those with PD also increased their stance phase durations (F(1,22)=7.426, P=0.012) for both obstacle conditions, while the CG maintained comparable step durations for all conditions. For the crossing phase, people with PD demonstrated shorter step length (F(1,22)=9.699, P=0.005) over the obstacle. Leading limbs were closer to the obstacle, before and after crossing. Thus PD hypokinesia compromises the approach and crossing phases of obstacle negotiation.

Early impairment of cognitive functions in Parkinson's disease

BACKGROUND: Impairment in non-motor functions such as disturbances of some executive functions are also common events in Parkinson's disease patients. OBJECTIVE: To verify the performance of Parkinson's disease patients in activities requiring visuoconstructive and visuospatial skills. METHOD: Thirty elderly patients with mild or moderate stages of Parkinson's disease were studied. The assessment of the clinical condition was based on the unified Parkinson's disease rating scale (56.28; SD=33.48), Hoehn and Yahr (2.2; SD=0.83), Schwab and England (78.93%), clock drawing test (7.36; SD=2.51), and mini-mental state examination (26.48; SD=10.11). Pearson's correlation and stepwise multiple regression were used for statistical analyses. RESULTS: The patients presented deterioration in visuospatial and visuoconstructive skills. CONCLUSION: The clock drawing test proved to be a useful predictive tool for identifying early cognitive impairment in thesbe individuals.