MRI- and MRS-derived hippocampal correlates of quantitative locomotor function in older adults

Rehabilitation Response in Tremor- and Non-Tremor-Dominant Parkinson Disease: A Task-fMRI Study

BACKGROUND

Tremor-dominant (TD) and nontremor-dominant (NTD) Parkinson's disease (PD) showed different responses to rehabilitation. However, the neural mechanism behind this remains unclear.

METHODS

This cohort study explores changes in motor function, brain activation, and functional connectivity following 2 weeks of rehabilitation in TD-PD and NTD-PD patients, respectively. A total of 11 TD-PD patients, 24 NTD-PD patients, and 21 age-matched healthy controls (HCs) were included. At baseline, all participants underwent functional magnetic resonance imaging (fMRI) while performing the foot tapping task. Motor symptoms, gait, balance, and task-based fMRI were then evaluated in patients before and after rehabilitation.

RESULTS

Compared to HCs, TD-PD patients showed increased activity in the left inferior frontal gyrus and the right insula, and NTD-PD patients showed increased activations in the left postcentral gyrus and decreased within-cerebellar connectivity at baseline. Rehabilitation improved motor function in PD patients regardless of motor subtype. TD-PD patients showed increased recruitments of the sensorimotor cortex and the bilateral thalamus after rehabilitation, and NTD-PD patients showed increased cerebellar activation and within-cerebellar connectivity that was associated with better motor performance.

CONCLUSIONS

This study demonstrated that rehabilitation-induced brain functional reorganization varied by motor subtypes in PD, which may have important implications for making individualized rehabilitation programs.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: ChiCTR1900020771.

Gray Matter Volumes Mediate the Relationship Between Disease Duration and Balance Control Performance in Chronic Ankle Instability

The relationship between structural changes in the cerebral gray matter and diminished balance control performance in patients with chronic ankle instability (CAI) has remained unclear. This paper aimed to assess the difference in gray matter volume (GMV) between participants with CAI and healthy controls (HC) and to characterize the role of GMV in the relationship between disease duration and balance performance in CAI. 42 participants with CAI and 33 HC completed the structural brain MRI scans, one-legged standing test, and Y-balance test. Regional GMV was measured by applying voxel-based morphometry methods. The result showed that, compared with HC, participants with CAI exhibited lower GMV in multiple brain regions (familywise error [FWE] corrected p < 0.021). Within CAI only, but not in HC, lower GMV in the thalamus (β = -0.53, p = 0.003) and hippocampus (β = -0.57, p = 0.001) was associated with faster sway velocity of the center of pressure (CoP) in eyes closed condition (i.e., worse balance control performance). The GMV in the thalamus (percentage mediated [PM] = 32.02%; indirect effect β = 0.119, 95% CI = 0.003 to 0.282) and hippocampus (PM = 33.71%; indirect effect β = 0.122, 95% CI = 0.005 to 0.278) significantly mediated the association between the disease duration and balance performance. These findings suggest that the structural characteristics of the supraspinal elements is critical to the maintenance of balance control performance in individuals suffering from CAI, which deserve careful consideration in the management and rehabilitation programs in this population.

Medial Temporal Lobe Atrophy in Older Adults With Subjective Cognitive Impairments Affects Gait Parameters in the Spatial Navigation Task

Both navigation abilities and gait can be affected by the atrophy in the medial temporal cortex. This study aimed to determine whether navigation abilities could differentiate seniors with and without medial temporal lobe atrophy who complained about their cognitive status. The participants, classified to either the medial temporal atrophy group (n = 23) or the control group (n = 22) underwent neuropsychological assessment and performed a spatial navigation task while their gait parameters were recorded. The study showed no significant differences between the two groups in memory, fluency, and semantic knowledge or typical measures of navigating abilities. However, gait parameters, particularly the propulsion index during certain phases of the navigation task, distinguished between seniors with and without medial temporal lobe lesions. These findings suggest that the gait parameters in the navigation task may be a valuable tool for identifying seniors with cognitive complaints and subtle medial temporal atrophy.

Exploring shared neural substrates underlying cognition and gait variability in adults without dementia

BACKGROUND

High gait variability is associated with neurodegeneration and cognitive impairments and is predictive of cognitive impairment and dementia. The objective of this study was to identify cortical or subcortical structures of the brain shared by gait variability measured using a body-worn tri-axial accelerometer (TAA) and cognitive function.

METHODS

This study is a part of a larger population-based cohort study on cognitive aging and dementia. The study included 207 participants without dementia, with a mean age of 72.6, and 45.4% of them are females. We conducted standardized diagnostic interview including a detailed medical history, physical and neurological examinations, and laboratory tests for cognitive impairment. We obtained gait variability during walking using a body-worn TAA along and measured cortical thickness and subcortical volume from brain magnetic resonance (MR) images. We cross-sectionally investigated the cortical and subcortical neural structures associated with gait variability and the shared neural substrates of gait variability and cognitive function.

RESULTS

Higher gait variability was associated with the lower cognitive function and thinner cortical gray matter but not smaller subcortical structures. Among the clusters exhibiting correlations with gait variability, one that included the inferior temporal, entorhinal, parahippocampal, fusiform, and lingual regions in the left hemisphere was also associated with global cognitive and verbal memory function. Mediation analysis results revealed that the cluster's cortical thickness played a mediating role in the association between gait variability and cognitive function.

CONCLUSION

Gait variability and cognitive function may share neural substrates, specifically in regions related to memory and visuospatial navigation.

Association Between the Loss of Gait Harmony and Cognitive Impairment: Cross-Sectional Study

BACKGROUND

Functional limitations and disabilities have been associated with a decrease in cognitive function due to increasing age. Gait performance and cognitive function have been associated with gait variability in executive function, the phase domain in memory, and gait abnormalities in cognitive decline.

OBJECTIVE

Our study aimed to investigate whether gait harmony was associated with cognitive function in the older adult population. Moreover, we aimed to investigate whether gait harmony was associated with cognitive function and explore each cognitive function in a specific harmonic state.

METHODS

The study population included 510 adults aged ≥60 years who visited the Department of Neurology at the Veterans Health Service Medical Center, Seoul, South Korea. Gait data were collected using a 3D motion capture device with a wireless inertial measurement unit system. For cognitive function assessments, we used the Seoul Neuropsychological Screening Battery-Core test, which evaluates the level of cognitive function or impairment in 5 cognitive domains.

RESULTS

In general, the association between the Seoul Neuropsychological Screening Battery-Core tests and the stance-to-swing ratio in the >1.63 ratio group yielded lower β coefficients than those in the 1.50-1.63 ratio group. After adjustment for confounders, the odds ratio (OR) for the Digit Symbol Coding test (adjusted OR 0.42, 95% CI 0.20-0.88) and the Korean version of the Color Word Stroop Test: 60 seconds (adjusted OR 0.51, 95% CI 0.29-0.89) for frontal and executive function were significantly lower for the >1.63 ratio group than the reference group.

CONCLUSIONS

Our findings suggest that the gait phase ratio is a valuable indicator of walking deficits and may also be associated with cognitive impairment in older adults.

Enhanced gait variability index and cognitive performance in Asian adults: Results from the Yishun Study

BACKGROUND

Although gait variability has been linked to cognitive decline among older adults, the lack of a comprehensive composite gait variability score has dampened the application of gait variability.

RESEARCH QUESTION

Does the enhanced gait variability index (EGVI) - a composite score gait variability index - provide differential and useful information on cognitive decline in community-dwelling adults from that using gait speed?

METHODS

Healthy community-dwelling adults (n = 311) aged 21-90 were individually administered the Repeatable Battery for the Assessment of Neuropsychological Status (RBANS). Habitual gait speed and spatiotemporal parameters were measured using a 6 m instrumented walkway system. The EGVI for each participant was calculated from five spatiotemporal parameters - step length(cm), step time(s), stance time(s), single support time(s) and stride velocity(cm/s). Linear regression models, controlling for age, gender, and education, were built to examine the independent effects of EGVI or gait speed on global cognition and individual domains.

RESULTS

Multiple regression revealed that gait speed contributed significantly to the performance of the domain "Attention" (p = 0.04) whereas EGVI contributed significantly for the performance of the domain "Visuospatial" (p = 0.04) and "Delayed Memory" (p = 0.02).

SIGNIFICANCE

EGVI provides differential and useful information from using gait speed alone. The EGVI may offer a solution to measure or track GV changes in relation to cognitive changes.

Pathological Gait Signatures of Post-stroke Dementia With Toe-Off and Heel-to-Ground Angles Discriminate From Alzheimer's Disease

Given the limited power of neuropsychological tests, there is a need for a simple, reliable means, such as gait, to identify mild dementia and its subtypes. However, gait characteristics of patients with post-stroke dementia (PSD) and Alzheimer’s disease (AD) are unclear. We sought to describe their gait signatures and to explore gait parameters distinguishing PSD from post-stroke non-dementia (PSND) and patients with AD. We divided 3-month post-stroke patients into PSND and PSD groups based on the Mini-Mental State Examination (MMSE), Montreal Cognitive Assessment (MoCA), and the activity of daily living (ADL). Thirty-one patients with AD and thirty-two healthy controls (HCs) were also recruited. Ten gait parameters in one single and two dual-task gait tests (counting-backward or naming-animals while walking) were compared among the groups, with adjustment for baseline demographic covariates and the MMSE score. The area under the receiver operating characteristic curve (AUC) was used to identify parameters discriminating PSD from individuals with PSND and AD. Patients with PSD and patients with AD showed impaired stride length, velocity, stride time, and cadence while patients with PSD had altered stance and swing phase proportions (all p ≤ 0.01, post hoc). Patients with AD had smaller toe-off (ToA) and heel-to-ground angles (HtA) (p ≤ 0.01) than HCs in dual-task gait tests. Individuals with PSD had a shorter stride length, slower velocity, and altered stance and swing phase percentages in all tests (p ≤ 0.01), but a higher coefficient of variation of stride length (CoV_SL) and time (CoV_ST) only in the naming animals-task gait test (p ≤ 0.001) than individuals with PSND. ToA and HtA in the naming animals-task gait test were smaller in individuals with AD than those with PSD (p ≤ 0.01). Statistical significance persisted after adjusting for demographic covariates, but not for MMSE. The pace and the percentage of stance or swing phase in all tests, CoV_ST in the dual-task paradigm, and CoV_SL only in the naming animals-task gait test (moderate accuracy, AUC > 0.700, p ≤ 0.01) could distinguish PSD from PSND. Furthermore, the ToA and HtA in the naming animals-task gait paradigm discriminated AD from PSD (moderate accuracy, AUC > 0.700, p ≤ 0.01). Thus, specific gait characteristics could allow early identification of PSD and may allow non-invasive discrimination between PSD and AD, or even other subtypes of dementia.

Associations between gait speed and brain structure in amnestic mild cognitive impairment: a quantitative neuroimaging study

BACKGROUND

Patients with amnestic mild cognitive impairment (aMCI) present gait disturbances including slower speed and higher variability when compared to cognitively healthy individuals (CHI). Brain neuroimaging could explore higher levels of motor control. Our purpose was to look for an association between morphometrics and gait parameters in each group. We hypothesized that the relation between morphological cerebral alteration and gait speed are different following the group.

METHODS

Fifty-three participants (30 with aMCI and 23 CHI) were recruited in this French cross-sectional study (mean 72 ± 5 years, 38% female). Gait speed and gait variability (coefficients of variation of stride time (STV) and stride length (SLV)) were measured using GAITrite® system. CAT12 software was used to analyse volume and surface morphometry like gray matter volume (GMV) and cortical thickness (CT). Age, gender and education level were used as potential cofounders.

RESULTS

aMCI had slower gait speed and higher STV when compared to CHI. In aMCI the full adjusted linear regression model showed that lower gait speed was associated with decreased GMV and lower CT in bilateral superior temporal gyri (p < 0.36). In CHI, no association was found between gait speed and brain structure. Higher SLV was correlated with reduced GMV in spread regions (p < 0.05) and thinner cortex in the middle right frontal gyrus (p = 0.001) in aMCI. In CHI, higher SLV was associated with reduced GMV in 1 cluster: the left lingual (p = 0.041).

CONCLUSIONS

These findings indicate that lower gait speed is associated with specific brain structural changes as reduced GMV and CT during aMCI.

The Associations Between Grey Matter Volume Covariance Patterns and Gait Variability-The Tasmanian Study of Cognition and Gait

Greater gait variability predicts dementia. However, little is known about the neural correlates of gait variability. The aims of this study were to determine (1) grey matter volume covariance patterns associated with gait variability and (2) whether these patterns were associated with specific cognitive domains. Participants (n = 351; mean age 71.9 ± 7.1) were randomly selected from the Southern Tasmanian electoral roll. Step time, step length, step width and double support time were measured using an electronic walkway. Gait variability was calculated as the standard deviation of all steps for each gait measure. Voxel-based morphometry and multivariate covariance-based analyses were used to identify grey matter patterns associated with each gait variability measure. The individual expressions of grey matter patterns were correlated with processing speed, memory, executive and visuospatial functions. The grey matter covariance pattern of double support time variability included frontal, medial temporal, anterior cingulate, insula, cerebellar and striatal regions. Greater expression of this pattern was correlated with poorer performance in all cognitive functions (p < 0.001). The covariance pattern of step length variability included frontal, temporal, insula, occipital and cerebellar regions and was correlated with all cognitive functions (p < 0.05), except memory (p = 0.76). The covariance pattern of step width variability was limited to the cerebellum and correlated only with memory (p = 0.047). No significant pattern was identified for step time variability. In conclusion, different grey matter covariance patterns were associated with individual gait variability measures. These patterns were also correlated with specific cognitive functions, suggesting common neural networks may underlie both gait and cognition.

Distinct cortical thickness patterns link disparate cerebral cortex regions to select mobility domains

The cortical control of gait and mobility involves multiple brain regions. Therefore, one could speculate that the association between specific spatial patterns of cortical thickness may be differentially associated with different mobility domains. To test this possibility, 115 healthy participants aged 27–82 (mean 60.5 ± 13.8) underwent a mobility assessment (usual-walk, dual-task walk, Timed Up and Go) and MRI scan. Ten mobility domains of relatively simple (e.g., usual-walking) and complex tasks (i.e., dual task walking, turns, transitions) and cortical thickness of 68 ROIs were extracted. All associations between mobility and cortical thickness were controlled for age and gender. Scaled Subprofile Modelling (SSM), a PCA-regression, identified thickness patterns that were correlated with the individual mobility domains, controlling for multiple comparisons. We found that lower mean global cortical thickness was correlated with worse general mobility (r = − 0.296, p = 0.003), as measured by the time to complete the Timed Up and Go test. Three distinct patterns of cortical thickness were associated with three different gait domains during simple, usual-walking: pace, rhythm, and symmetry. In contrast, cortical thickness patterns were not related to the more complex mobility domains. These findings demonstrate that robust and topographically distinct cortical thickness patterns are linked to select mobility domains during relatively simple walking, but not to more complex aspects of mobility. Functional connectivity may play a larger role in the more complex aspects of mobility.

Regional Associations of Cortical Thickness With Gait Variability—The Tasmanian Study of Cognition and Gait

Background

Gait variability is a marker of cognitive decline. However, there is limited understanding of the cortical regions associated with gait variability. We examined associations between regional cortical thickness and gait variability in a population-based sample of older people without dementia.

Method

Participants (n = 350, mean age 71.9 ± 7.1) were randomly selected from the electoral roll. Variability in step time, step length, step width, and double support time (DST) were calculated as the standard deviation of each measure, obtained from the GAITRite walkway. Magnetic resonance imaging (MRI) scans were processed through FreeSurfer to obtain cortical thickness of 68 regions. Bayesian regression was used to determine regional associations of mean cortical thickness and thickness ratio (regional thickness/overall mean thickness) with gait variability.

Results

Smaller global cortical thickness was only associated with greater step width and step time variability. Smaller mean thickness in widespread regions important for sensory, cognitive, and motor functions were associated with greater step width and step time variability. In contrast, smaller thickness in a few frontal and temporal regions were associated with DST variability and the right cuneus was associated with step length variability. Smaller thickness ratio in frontal and temporal regions important for motor planning, execution, and sensory function and greater thickness ratio in the anterior cingulate was associated with greater variability in all measures.

Conclusions

Examining individual cortical regions is important in understanding the relationship between gray matter and gait variability. Cortical thickness ratio highlights that smaller regional thickness relative to global thickness may be important for the consistency of gait.

The neural correlates of discrete gait characteristics in ageing: A structured review

Gait is complex, described by diverse characteristics underpinned by widespread central nervous system networks including motor and cognitive functions. Despite this, neural substrates of discrete gait characteristics are poorly understood, limiting understanding of gait impairment in ageing and disease. This structured review aims to map gait characteristics, defined from a pre-specified model reflecting independent gait domains, to brain imaging parameters in older adults. Fifty-two studies of 38,029 yielded were reviewed. Studies showed inconsistent approaches when mapping gait assessment to neural substrates, limiting conclusions. Gait impairments typically associated with brain deterioration, specifically grey matter atrophy and white matter integrity loss. Gait velocity, a global measure of gait control, was most frequently associated with these imaging markers within frontal and basal ganglia regions, and its decline predicted from white matter volume and integrity measurements. Fewer studies assessed additional gait measures or functional imaging parameters. Future studies mapping regional neuroanatomical and functional correlates of gait are needed, including those which take a multi-process network perspective to better understand mobility in health and disease.

Limbic and Basal Ganglia Neuroanatomical Correlates of Gait and Executive Function: Older Adults With Mild Cognitive Impairment and Intact Cognition

OBJECTIVE

This study aimed to examine differences in spatiotemporal gait parameters between older adults with amnestic mild cognitive impairment and normal cognition and to examine limbic and basal ganglia neural correlates of gait and executive function in older adults without dementia.

DESIGN

This was a cross-sectional study of 46 community-dwelling older adults, ages 70-95 yrs, with amnestic mild cognitive impairment (n = 23) and normal cognition (n = 23). Structural magnetic resonance imaging was used to attain volumetric measures of limbic and basal ganglia structures. Quantitative motion analysis was used to measure spatiotemporal parameters of gait. The Trail Making Test was used to assess executive function.

RESULTS

During fast-paced walking, older adults with amnestic mild cognitive impairment demonstrated significantly slower gait speed and shorter stride length compared with older adults with normal cognition. Stride length was positively correlated with hippocampal, anterior cingulate, and nucleus accumbens volumes (P < 0.05). Executive function was positively correlated with hippocampal, anterior cingulate, and posterior cingulate volumes (P < 0.05).

CONCLUSIONS

Compared with older adults with normal cognition, those with amnestic mild cognitive impairment demonstrated slower gait speed and shorter stride length, during fast-paced walking, and lower executive function. Hippocampal and anterior cingulate volumes demonstrated moderate positive correlation with both gait and executive function, after adjusting for age.

TO CLAIM CME CREDITS

Complete the self-assessment activity and evaluation online at http://www.physiatry.org/JournalCME CME OBJECTIVES: Upon completion of this article, the reader should be able to: (1) discuss gait performance and cognitive function in older adults with amnestic mild cognitive impairment versus normal cognition, (2) discuss neurocorrelates of gait and executive function in older adults without dementia, and (3) recognize the importance of assessing gait speed and cognitive function in the clinical management of older adults at risk for dementia.

LEVEL

Advanced ACCREDITATION: The Association of Academic Physiatrists is accredited by the Accreditation Council for Continuing Medical Education to provide continuing medical education for physicians.The Association of Academic Physiatrists designates this Journal-based CME activity for a maximum of 0.5 AMA PRA Category 1 Credit(s)™. Physicians should only claim credit commensurate with the extent of their participation in the activity.

Association of hippocampal volume with gait variability in pre-dementia and dementia stages of Alzheimer disease: Results from a cross-sectional study

BACKGROUND

Decreased hippocampal volume is a biomarker of Alzheimer disease (AD). The association of hippocampal volume with gait variability across the spectrum of AD, especially in early stages, has been few studied. The study aims to examine the association of hippocampal volume with the coefficient of variation (CoV) of stride time in individuals with mild and moderate to severe subjective cognitive impairment (SCI), non-amnestic mild cognitive impairment (na-MCI), amnestic mild cognitive impairment (a-MCI), and mild to moderate AD dementia.

METHODS

271 individuals (79 mild SCI, 68 moderate to severe SCI, 47 na-MCI, 42 a-MCI and 35 mild to moderate AD dementia) were included in this cross-sectional study. Hippocampal volume was quantified from a three-dimensional T₁-weighted MRI. CoV of stride time was recorded at self-selected pace with an electronic walkway. Age, sex, body mass index, number of drugs daily taken, history of falls, walking speed, type of MRI scanner, total intracranial volume, and white matter volume abnormality were used as covariates.

RESULTS

Participants with moderate to severe SCI had a higher CoV of stride time compared to those with mild SCI and na-MCI (P < 0.010), and a higher hippocampal volume compared to other groups (P ≤ 0.001). Participants with moderate to severe SCI had increased hippocampal volume associated with increased CoV of stride time (coefficient of regression β = 0.750 with P = 0.041), while the other groups did not show any significant association.

CONCLUSIONS

A positive association between greater hippocampal volume (i.e., better brain morphological structure) and an increased stride time variability (i.e., worse gait performance) in individuals with moderate to severe SCI is reported. This association confirms the key role of the hippocampus in gait control and suggests an inefficient compensatory mechanism in early stages of pathological aging like AD.

Slow gait as a motor marker of mild cognitive impairment? the relationships between functional mobility and mild cognitive impairment

The purpose of this study was to evaluate the association between functional mobility and mild cognitive impairment in older adults. A total of 800 older adults were recruited (653 controls and 147 subjects with MCI [88 subjects with aMCI and 59 subjects with naMCI]). Motor performance was measured with the Timed Up and Go test (TUG). The demographic factors associated with MCI were: age (OR = 1.05; 95% CI: 1.01-1.09) and the level of education (OR = 0.73; 95% CI: 0.68-0.79). An independent clinical factor associated with MCI was the TUG (OR = 1.14; 95% CI: 1.03-1.27). In the aMCI group, the relation between the TUG and cognitive status occurred (OR = 1.15; 95% CI: 1.02-1.31), whereas in the naMCI group this relationship was not observed. There is an association between cognitive dysfunction and impaired motor performance in older adults with MCI.

Risk factors for falls in terms of attention during gait in community-dwelling older adults

AIM

We examined factors related to conditions of life function and falls, including eye movements and gait variability, in community-dwelling older adults in Japan.

METHODS

Participants were 82 older adults (21 men, 61 women, mean age 76.1 years). We measured eye movements and gait variability during walking, and cognitive, attentional and life function. We compared two groups according to their fall history, and used a multiple logistic regression analysis to determine its relevance.

RESULTS

Fixation time, which was estimated from eye movements during obstacle crossing, and gait variability (vertical) were significantly associated with falls. There was also a significant correlation between fixation time and gait variability during obstacle crossing. In other words, the higher the gait variability in older adults, the higher the risk of falls, which was due to reduced attention estimated from eye movements during obstacle crossing that required obstacle avoidance.

CONCLUSIONS

These results show that poor attention during gait is a critical risk factor for falls in community-dwelling older adults. For fall prevention, it is necessary to promote exercises for attention, and to maintain an older adult-friendly pedestrian environment. Geriatr Gerontol Int 2018; 18: 1267-1271.

Subjective Memory Impairment and Gait Variability in Cognitively Healthy Individuals: Results from a Cross-Sectional Pilot Study

BACKGROUND

Increased stride time variability has been associated with memory impairment in mild cognitive impairment. Subjective memory impairment (SMI) is considered the earliest clinical stage of Alzheimer's disease (AD). The association between increased stride time variability and SMI has not been reported.

OBJECTIVE

This study aims to examine the association of stride time variability while performing single and dual tasking with SMI in cognitively healthy individuals (CHI).

METHODS

A total of 126 CHI (15 without SMI, 69 with SMI expressed by participants, 10 with SMI expressed by participant's relative, and 32 with SMI expressed by both participants and their relatives) were included in this cross-sectional study. The coefficient of variation (CoV) of stride time and walking speed were recorded under usual condition and while counting backwards. Age, gender, body mass index, number of drugs taken daily, use of psychoactive drugs, fear of falling, history of previous falls, and walking speed were used as covariates.

RESULTS

The multiple linear regression models showed that greater CoV of stride time while counting backwards, but not while single tasking, was associated with a participant's relative SMI (p = 0.038).

CONCLUSION

This study found a specific association between SMI expressed by a participant's relative and a greater CoV of stride time (i.e., worse performance) while dual tasking, suggesting that the association between gait variability and memory may be present in the earliest stages of memory impairment. Thus, gait variability under dual-task in individuals with SMI expressed by their relatives can be a potential biomarker of AD.

Association of Dual-Task Gait With Incident Dementia in Mild Cognitive Impairment: Results From the Gait and Brain Study

Importance

Gait performance is affected by neurodegeneration in aging and has the potential to be used as a clinical marker for progression from mild cognitive impairment (MCI) to dementia. A dual-task gait test evaluating the cognitive-motor interface may predict dementia progression in older adults with MCI.

Objective

To determine whether a dual-task gait test is associated with incident dementia in MCI.

Design, Setting, and Participants

The Gait and Brain Study is an ongoing prospective cohort study of community-dwelling older adults that enrolled 112 older adults with MCI. Participants were followed up for 6 years, with biannual visits including neurologic, cognitive, and gait assessments. Data were collected from July 2007 to March 2016.

Main Outcomes and Measures

Incident all-cause dementia was the main outcome measure, and single- and dual-task gait velocity and dual-task gait costs were the independent variables. A neuropsychological test battery was used to assess cognition. Gait velocity was recorded under single-task and 3 separate dual-task conditions using an electronic walkway. Dual-task gait cost was defined as the percentage change between single- and dual-task gait velocities: ([single-task gait velocity - dual-task gait velocity]/ single-task gait velocity) × 100. Cox proportional hazard models were used to estimate the association between risk of progression to dementia and the independent variables, adjusted for age, sex, education, comorbidities, and cognition.

Results

Among 112 study participants with MCI, mean (SD) age was 76.6 (6.9) years, 55 were women (49.1%), and 27 progressed to dementia (24.1%), with an incidence rate of 121 per 1000 person-years. Slow single-task gait velocity (<0.8 m/second) was not associated with progression to dementia (hazard ratio [HR], 3.41; 95% CI, 0.99-11.71; P = .05)while high dual-task gait cost while counting backward (HR, 3.79; 95% CI, 1.57-9.15; P = .003) and naming animals (HR, 2.41; 95% CI, 1.04-5.59; P = .04) were associated with dementia progression (incidence rate, 155 per 1000 person-years). The models remained robust after adjusting by baseline cognition except for dual-task gait cost when dichotomized.

Conclusions and Relevance

Dual-task gait is associated with progression to dementia in patients with MCI. Dual-task gait testing is easy to administer and may be used by clinicians to decide further biomarker testing, preventive strategies, and follow-up planning in patients with MCI.

Trial Registration

clinicaltrials.gov: NCT03020381.

Slowing gait and risk for cognitive impairment: The hippocampus as a shared neural substrate

OBJECTIVE

To identify the shared neuroimaging signature of gait slowing and cognitive impairment.

METHODS

We assessed a cohort of older adults (n = 175, mean age 73 years, 57% female, 65% white) with repeated measures of gait speed over 14 years, MRI for gray matter volume (GMV) at year 10 or 11, and adjudicated cognitive status at year 14. Gait slowing was calculated by bayesian slopes corrected for intercepts, with higher values indicating faster decline. GMV was normalized to intracranial volume, with lower values indicating greater atrophy for 10 regions of interest (hippocampus, anterior and posterior cingulate, primary and supplementary motor cortices, posterior parietal lobe, middle frontal lobe, caudate, putamen, pallidum). Nonparametric correlations adjusted for demographics, comorbidities, muscle strength, and knee pain assessed associations of time to walk with GMV. Logistic regression models calculated odds ratios (ORs) of gait slowing with dementia or mild cognitive impairment with and without adjustment for GMV.

RESULTS

Gait slowing was associated with cognitive impairment at year 14 (OR per 0.1 s/y slowing 1.47; 95% confidence interval 1.04-2.07). The right hippocampus was the only region that was related to both gait slowing (ρ = -0.16, p = 0.03) and cognitive impairment (OR 0.17, p = 0.009). Adjustment for right hippocampal volume attenuated the association of gait slowing with cognitive impairment by 23%.

CONCLUSIONS

The association between gait slowing and cognitive impairment is supported by a shared neural substrate that includes a smaller right hippocampus. This finding underscores the value of long-term gait slowing as an early indicator of dementia risk.

Effects of exercise on brain activity during walking in older adults: a randomized controlled trial

BACKGROUND

Physical activity may preserve neuronal plasticity, increase synapse formation, and cause the release of hormonal factors that promote neurogenesis and neuronal function. Previous studies have reported enhanced neurocognitive function following exercise training. However, the specific cortical regions activated during exercise training remain largely undefined. In this study, we quantitatively and objectively evaluated the effects of exercise on brain activity during walking in healthy older adults.

METHODS

A total of 24 elderly women (75-83 years old) were randomly allocated to either an intervention group or a control group. Those in the intervention group attended 3 months of biweekly 90-min sessions focused on aerobic exercise, strength training, and physical therapy. We monitored changes in regional cerebral glucose metabolism during walking in both groups using positron emission tomography (PET) and [¹⁸F]fluorodeoxyglucose (FDG).

RESULTS

All subjects completed the 3-month experiment and the adherence to the exercise program was 100%. Compared with the control group, the intervention group showed a significantly greater step length in the right foot after 3 months of physical activity. The FDG-PET assessment revealed a significant post-intervention increase in regional glucose metabolism in the left posterior entorhinal cortex, left superior temporal gyrus, and right superior temporopolar area in the intervention group. Interestingly, the control group showed a relative increase in regional glucose metabolism in the left premotor and supplemental motor areas, left and right somatosensory association cortex, and right primary visual cortex after the 3-month period. We found no significant differences in FDG uptake between the intervention and control groups before vs. after the intervention.

CONCLUSION

Exercise training increased activity in specific brain regions, such as the precuneus and entorhinal cortices, which play an important role in episodic and spatial memory. Further investigation is required to confirm whether alterations in glucose metabolism within these regions during walking directly promote physical and cognitive performance.

TRIAL REGISTRATION

UMIN-CTR ( UMIN000021829 ). Retrospectively registered 10 April 2016.

Gait disorders in the elderly and dual task gait analysis: a new approach for identifying motor phenotypes

BACKGROUND

Gait disorders and gait analysis under single and dual-task conditions are topics of great interest, but very few studies have looked for the relevance of gait analysis under dual-task conditions in elderly people on the basis of a clinical approach.

METHODS

An observational study including 103 patients (mean age 76.3 ± 7.2, women 56%) suffering from gait disorders or memory impairment was conducted. Gait analysis under dual-task conditions was carried out for all patients. Brain MRI was performed in the absence of contra-indications. Three main gait variables were measured: walking speed, stride frequency, and stride regularity. For each gait variable, the dual task cost was computed and a quartile analysis was obtained. Nonparametric tests were used for all the comparisons (Wilcoxon, Kruskal-Wallis, Fisher or Chi2 tests).

RESULTS

Four clinical subgroups were identified: gait instability (45%), recurrent falls (29%), memory impairment (18%), and cautious gait (8%). The biomechanical severity of these subgroups was ordered according to walking speed and stride regularity under both conditions, from least to most serious as follows: memory impairment, gait instability, recurrent falls, cautious gait (p < 0.01 for walking speed, p = 0.05 for stride regularity). According to the established diagnoses of gait disorders, 5 main pathological subgroups were identified (musculoskeletal diseases (n = 11), vestibular diseases (n = 6), mild cognitive impairment (n = 24), central nervous system pathologies, (n = 51), and without diagnosis (n = 8)). The dual task cost for walking speed, stride frequency and stride regularity were different among these subgroups (p < 0.01). The subgroups mild cognitive impairment and central nervous system pathologies both showed together a higher dual task cost for each variable compared to the other subgroups combined (p = 0.01). The quartile analysis of dual task cost for stride frequency and stride regularity allowed the identification of 3 motor phenotypes (p < 0.01), without any difference for white matter hyperintensities, but with an increased Scheltens score from the first to the third motor phenotype (p = 0.05).

CONCLUSIONS

Gait analysis under dual-task conditions in elderly people suffering from gait disorders or memory impairment is of great value in assessing the severity of gait disorders, differentiating between peripheral pathologies and central nervous system pathologies, and identifying motor phenotypes. Correlations between motor phenotypes and brain imaging require further studies.

The brain map of gait variability in aging, cognitive impairment and dementia-A systematic review

While gait variability may reflect subtle changes due to aging or cognitive impairment (CI), associated brain characteristics remain unclear. We summarize structural and functional neuroimaging findings associated with gait variability in older adults with and without CI and dementia. We identified 17 eligible studies; all were cross-sectional; few examined multiple brain areas. In older adults, temporal gait variability was associated with structural differences in medial areas important for lower limb coordination and balance. Both temporal and spatial gait variability were associated with structural and functional differences in hippocampus and primary sensorimotor cortex and structural differences in anterior cingulate cortex, basal ganglia, association tracts, and posterior thalamic radiation. In CI or dementia, some associations were found in primary motor cortex, hippocampus, prefrontal cortex and basal ganglia. In older adults, gait variability may be associated with areas important for sensorimotor integration and coordination. To comprehend the neural basis of gait variability with aging and CI, longitudinal studies of multiple brain areas are needed.

The developmental dynamics of gait maturation with a focus on spatiotemporal measures

Gait analysis is recognised as a powerful clinical tool for studying relationships between motor control and brain function. By drawing on the literature investigating gait in individuals with neurological disorders, this review provides insight into the neural processes that contribute to and regulate specific spatiotemporal sub-components of gait and how they may mature across early to late childhood. This review also discusses the roles of changing anthropomorphic characteristics, and maturing sensory and higher-order cognitive processes in differentiating the developmental trajectories of the sub-components of gait. Importantly, although studies have shown that cognitive-gait interference is larger in children compared to adults, the contributing neurocognitive mechanisms may vary across age groups who have different types of attentional or cognitive vulnerabilities. These findings have implications for current models of gait maturation by highlighting the need for a dynamic model that focuses on the integration of various factors that contribute to gait though experience and practice. This is essential to elucidating why gait and other motor deficits are often contiguous with cognitive neurodevelopmental disorders.

Association between Various Brain Pathologies and Gait Disturbance

BACKGROUND

Approximately 30% of older adults have disrupted gait. It is associated with increased risk of cognitive decline, disability, dementia, and death. Additionally, most older adults present with 1 or more neuropathologies at autopsy. Recently, there has been an effort to investigate the association between subclinical neuropathology and gait.

SUMMARY

We reviewed studies that investigated the association between gait and neuropathologies. Although all pathologies reviewed were associated with gait, grey matter atrophy was most consistently linked with poorer gait performance. Studies investigating the association between white matter and gait focused primarily on total white matter. Future research using more parsed regional analysis will provide more insight into this relationship. Evidence from studies investigating neuronal activity and gait suggests that gait disruption is associated with both under- and overactivation. Additional research is needed to delineate these conflicting results. Lastly, early evidence suggests that both amyloid and tau aggregation negatively impact multiple gait parameters, but additional studies are warranted. Overall, there was substantial methodological heterogeneity and a paucity of longitudinal studies. Key Messages: Longitudinal studies mapping changes in different types of neuropathology as they relate to changes in multiple gait parameters are needed to better understand trajectories of pathology and gait.

Association Between Falls and Brain Subvolumes: Results from a Cross-Sectional Analysis in Healthy Older Adults

Falls are a consequence of gait instability. Cortical and subcortical abnormalities have been associated with gait instability but not yet with falls. This study aims to compare the global and regional brain subvolumes between healthy older fallers and non-fallers. A total of 77 healthy older individuals (23 fallers and 54 non-fallers, 69.8 ± 3.5 years; 45.5 % female) were included in this study using a cross-sectional design. Based on an a priori hypothesis, the following brain subvolumes were quantified from three-dimensional T₁-weighted MRI using FreeSurfer software: total white matter abnormalities, total white matter, total cortical and subcortical gray matter, hippocampus, motor cortex, somatosensory cortex, premotor cortex, prefrontal cortex and parietal cortex volumes. Gait performances were also recorded. Age, sex, body mass index, comorbidities, use of psychoactive drugs, far-distance visual acuity, lower-limb proprioception, depressive symptoms and cognitive scores (Mini-Mental State Examination, Frontal Assessment Battery) were used as covariates. Fallers have more frequently depressive symptoms (P = 0.048), a lower far distance visual acuity (P = 0.026) and a higher coefficient of variation of stride time (P = 0.008) compared to non-fallers. There was a trend to greater subvolumes for the somatosensory cortex (P = 0.093) and the hippocampus (P = 0.060) in the falls group. Multiple logistic regressions showed that subvolumes of the somatosensory cortex and the hippocampus (P < 0.042) were increased in fallers compared to non-fallers, even after adjustment for clinical and brain characteristics. The greater subvolumes of the somatosensory cortex and hippocampus reported in fallers compared to non-fallers suggests a possible brain compensatory mechanism involving spatial navigation and integration of sensory information.

Apolipoprotein E Genotype Linked to Spatial Gait Characteristics: Predictors of Cognitive Dual Task Gait Change

Background

Developing measures to detect preclinical Alzheimer’s Disease is vital, as prodromal stage interventions may prove more efficacious in altering the disease’s trajectory. Gait changes may serve as a useful clinical heuristic that precedes cognitive decline. This study provides the first systematic investigation of gait characteristics relationship with relevant demographic, physical, genetic (Apolipoprotein E genotype), and health risk factors in non-demented older adults during a cognitive-load dual task walking condition.

Methods

The GAITRite system provided objective measurement of gait characteristics in APOE-e4 “carriers” (n = 75) and “non-carriers” (n = 224). Analyses examined stride length and step time gait characteristics during simple and dual-task (spelling five-letter words backwards) conditions in relation to demographic, physical, genetic, and health risk factors.

Results

Slower step time and shorter stride length associated with older age, greater health risk, and worse physical performance (ps < .05). Men and women differed in height, gait characteristics, health risk factors and global cognition (ps < .05). APOE-e4 associated with a higher likelihood of hypercholesterolemia and overall illness index scores (ps < .05). No genotype-sex interactions on gait were found. APOE-e4 was linked to shorter stride length and greater dual-task related disturbances in stride length.

Conclusions

Stride length has been linked to heightened fall risk, attention decrements and structural brain changes in older adults. Our results indicate that stride length is a useful behavioral marker of cognitive change that is associated with genetic risk for AD. Sex disparities in motor decline may be a function of health risk factors.

Subcortical Volumes Differ in Parkinson's Disease Motor Subtypes: New Insights into the Pathophysiology of Disparate Symptoms

Objectives: Patients with Parkinson’s disease (PD) can be classified, based on their motor symptoms into the Postural Instability Gait Difficulty (PIGD) subtype or the Tremor Dominant (TD) subtype. Gray matter changes between the subtypes have been reported using whole brain Voxel-Based Morphometry (VBM), however, the evaluation of subcortical gray matter volumetric differences between these subtypes using automated volumetric analysis has only been studied in relatively small sample sizes and needs further study to confirm that the negative findings were not due to the sample size. Therefore, we aimed to evaluate volumetric changes in subcortical regions and their association with PD motor subtypes.

Methods: Automated volumetric magnetic resonance imaging (MRI) analysis quantified the subcortical gray matter volumes of patients with PD in the PIGD subtype (n = 30), in the TD subtype (n = 30), and in 28 healthy controls (HCs).

Results: Significantly lower amygdala and globus pallidus gray matter volume was detected in the PIGD, as compared to the TD subtype, with a trend for an association between globus pallidus degeneration and higher (worse) PIGD scores. Furthermore, among all the patients with PD, higher hippocampal volumes were correlated with a higher (better) dual tasking gait speed (r = 0.30, p < 0.002) and with a higher global cognitive score (r = 0.36, p < 0.0001). Lower putamen volume was correlated with a higher (worse) freezing of gait score (r = −0.28, p < 0.004), an episodic symptom which is common among the PIGD subtype. As expected, differences detected between HCs and patients in the PD subgroups included regions within the amygdala and the dorsal striatum but not the ventral striatum, a brain region that is generally considered to be more preserved in PD.

Conclusions: The disparate patterns of subcortical degeneration can explain some of the differences in symptoms between the PD subtypes such as gait disturbances and cognitive functions. These findings may, in the future, help to inform a personalized therapeutic approach.

Structural neural correlates of impaired mobility and subsequent decline in executive functions: a 12-month prospective study

Impaired mobility, such as falls, may be an early biomarker of subsequent cognitive decline and is associated with subclinical alterations in both brain structure and function. In this 12-month prospective study, we examined whether there are volumetric differences in gray matter and subcortical regions, as well as cerebral white matter, between older fallers and non-fallers. In addition, we assessed whether these baseline volumetric differences are associated with changes in cognitive function over 12months. A total of 66 community-dwelling older adults were recruited and categorized by their falls status. Magnetic resonance imaging occurred at baseline and participants' physical and cognitive performances were assessed at baseline and 12-months. At baseline, fallers showed significantly lower volumes in gray matter, subcortical regions, and cerebral white matter compared with non-fallers. Notably, fallers had significantly lower left lateral orbitofrontal white matter volume. Moreover, lower left lateral orbitofrontal white matter volume at baseline was associated with greater decline in set-shifting performance over 12months. Our data suggest that falls may indicate subclinical alterations in regional brain volume that are associated with subsequent decline in executive functions.

Gait speed or gait variability, which one to use as a marker of risk to develop Alzheimer disease? A pilot study

BACKGROUND

Previous literature demonstrates the interest of gait analysis to predict cognitive decline in old people.

AIMS

This pilot study aims to determine if gait speed or gait variability is a marker able to early identify, among mild cognitive impairment (MCI) subjects, those at risk to develop Alzheimer's disease (AD) in the future.

METHODS

13 MCI subjects were included in 2007. Their gait parameters (walking speed, stride length and gait frequency, regularity and symmetry) were measured in 2007 and 2008 in simple task (ST) and in dual task (DT) using a triaxial accelerometer (Locometrix(®)). Among the 13 MCI subjects included in 2007, 10 were assessed in 2008. So, 23 (13 in 2007 + 10 in 2008) gait tests were collected. In 2011, MCI people were considered as "MCI+" when they developed AD (between baseline and 2011) and as "MCI-" if they did not. Among the 23 gait tests, 15 were from MCI+ (9 gait tests in 2007 and 6 in 2008) and 8 from MCI- (4 gait tests in 2007 and 4 gait tests in 2008). Mann-Whitney non-parametric U test was used to compare gait parameters of MCI+ and MCI-.

RESULTS

Gait speed, symmetry and regularity were lower in MCI+ than in MCI-.

DISCUSSION

Despite the small sample size, the results presented in this original pilot study are in line as the infrequent previous literature related to this topic. The authors discuss lacks and strengths of this work.

CONCLUSIONS

These results suggest that both gait speed and gait variability could be markers to early identify MCI at risk to develop AD.

Association of Motoric Cognitive Risk Syndrome With Brain Volumes: Results From the GAIT Study

BACKGROUND

The "motoric cognitive risk" (MCR) syndrome is a newly reported predementia syndrome combining cognitive complaint and slow gait speed. We hypothesized that individuals with MCR syndrome would have lower brain volumes compared with non-MCR individuals. This study aims (i) to compare the cognitive profile of nondemented older community-dwellers with and without MCR syndrome and (ii) to examine association of global and regional brain volumes with MCR syndrome.

METHODS

A total of 171 individuals (28 MCR and 143 non-MCR) were included in this cross-sectional study. Total white matter abnormalities, total white matter, total cortical and subcortical gray matters, hippocampus, motor cortex, premotor cortex, and prefrontal cortex were examined. Brain volumes were quantified from a three-dimensional T1-weighted magnetic resonance imaging using semi-automated software. Age, gender, education level, number of drugs taken daily, use of psychoactive drugs, and cognitive profile were also measured.

RESULTS

The distribution of cognitively healthy individuals and those with mild cognitive impairment was not different in participants with and without MCR. Multiple logistic regression models showed that smaller volumes of total gray matter (p = .016), total cortical gray matter (p = .010), premotor cortex (p = .018), prefrontal cortex (p = .026), and dorsolateral segment of prefrontal cortex (p = .032) were associated with MCR status. The premotor cortex presented the highest mean difference for brain regional volume between MCR and non-MCR participants (p = .03).

CONCLUSIONS

The findings revealed similar cognitive profile in MCR and non-MCR participants, and MCR-related smaller global and regional gray matter volumes involving premotor and prefrontal cortices, suggesting that the MCR syndrome may predict cortical neurodegenerative dementia more than subcortical dementia.

Lower gray matter integrity is associated with greater lap time variation in high-functioning older adults

BACKGROUND

Lower integrity of cerebral gray matter is associated with higher gait variability. It is not known whether gray matter integrity is associated with higher lap time variation (LTV), a clinically accessible measure of gait variability, high levels of which have been associated with mortality. This study examines the cross-sectional association between gray matter mean diffusivity (MD) and LTV in community-dwelling older adults.

METHODS

Study participants consisted of 449 high-functioning adults aged 50 and older (56.8% female) in the Baltimore Longitudinal Study of Aging, free of overt neurological disease. The magnitude of MD in the gray matter, a measure of impaired tissue integrity, was assessed by diffusion tensor imaging in 16 regions of interest (ROIs) involved with executive function, sensorimotor function, and memory. LTV was assessed as variability in lap time based on individual trajectories over ten 40-m laps. Age, sex, height, and weight were covariates. The model additionally adjusted for mean lap time and health conditions that may affect LTV.

RESULTS

Higher levels of average MD across 16 ROIs were significantly associated with higher LTV after adjustment for covariates. Specifically, higher MD in the precuneus and the anterior and middle cingulate cortices was strongly associated with higher LTV, as compared to other ROIs. The association persisted after adjustment for mean lap time, hypertension, and diabetes.

CONCLUSIONS

Lower gray matter integrity in selected areas may underlie greater LTV in high-functioning community-dwelling older adults. Longitudinal studies are warranted to examine whether changes in gray matter integrity precede more variable gait.

Brain volume changes in gait control in patients with mild cognitive impairment compared to cognitively healthy individuals; GAIT study results

BACKGROUND

Differences in brain structures involved in gait control between normal and pathological aging are still matter of debate. This study aims to compare the regional and global brain volume patterns associated with gait performances assessed with Timed Up and Go test (TUG) between cognitively healthy individuals (CHI) and patients with mild cognitive impairment (MCI).

MATERIAL AND METHODS

A total of 171 (80 CHI, 25 with amnestic MCI [a-MCI] and 66 with non-amnestic MCI [na-MCI]) participants (70.2±4.0years; 37% female) consecutively realized (rTUG) and imagined (iTUG) the TUG. rTUG measures the time needed to rise from a chair, walk 3m, turn around and return to a seated position and iTUG represents the validated imagined version of the TUG. Global and regional brain volumes were quantified from three-dimensional T1-weighted MRI using a semi-automated software.

RESULTS

Linear regression models show that increased rTUG (i.e. worse performance) was associated with lower total white matter, total gray matter, left and right hippocampal volume in patients with na-MCI (P<0.045), and with lower right hippocampal volume in CHI (P=0.013). Increased iTUG was associated with lower gray matter and left premotor cortex volumes in patients with na-MCI (P<0.05).

CONCLUSIONS

The findings showed different patterns of brain volume reduction associated with increased rTUG and iTUG between CHI and MCI patients, except for the right hippocampal volume which was smaller in both groups.

Gait phenotype from mild cognitive impairment to moderate dementia: results from the GOOD initiative

BACKGROUND AND PURPOSE

The differences in gait abnormalities from the earliest to the later stages of dementia and in the different subtypes of dementia have not been fully examined. This study aims to compare spatiotemporal gait parameters in cognitively healthy individuals, patients with amnestic mild cognitive impairment (MCI) and non-amnestic MCI, and patients with mild and moderate stages of Alzheimer's disease (AD) and non-Alzheimer's disease (non-AD).

METHODS

Based on a cross-sectional design, 1719 participants (77.4 ± 7.3 years, 53.9% female) were recruited from cohorts from seven countries participating in the Gait, Cognition and Decline (GOOD) initiative. Mean values and coefficients of variation of spatiotemporal gait parameters were measured during normal pace walking with the GAITRite system at all sites.

RESULTS

Performance of spatiotemporal gait parameters declined in parallel with the stage of cognitive decline from MCI status to moderate dementia. Gait parameters of patients with non-amnestic MCI were more disturbed compared to patients with amnestic MCI, and MCI subgroups performed better than demented patients. Patients with non-AD dementia had worse gait performance than those with AD dementia. This degradation of gait parameters was similar between mean values and coefficients of variation of spatiotemporal gait parameters in the earliest stages of cognitive decline, but different in the most advanced stages, especially in the non-AD subtypes.

CONCLUSIONS

Spatiotemporal gait parameters were more disturbed in the advanced stages of dementia, and more affected in the non-AD dementias than in AD. These findings suggest that quantitative gait parameters could be used as a surrogate marker for improving the diagnosis of dementia.

Multicomponent physical exercise with simultaneous cognitive training to enhance dual-task walking of older adults: a secondary analysis of a 6-month randomized controlled trial with 1-year follow-up

BACKGROUND

About one-third of people older than 65 years fall at least once a year. Physical exercise has been previously demonstrated to improve gait, enhance physical fitness, and prevent falls. Nonetheless, the addition of cognitive training components may potentially increase these effects, since cognitive impairment is related to gait irregularities and fall risk. We hypothesized that simultaneous cognitive-physical training would lead to greater improvements in dual-task (DT) gait compared to exclusive physical training.

METHODS

Elderly persons older than 70 years and without cognitive impairment were randomly assigned to the following groups: 1) virtual reality video game dancing (DANCE), 2) treadmill walking with simultaneous verbal memory training (MEMORY), or 3) treadmill walking (PHYS). Each program was complemented with strength and balance exercises. Two 1-hour training sessions per week over 6 months were applied. Gait variables, functional fitness (Short Physical Performance Battery, 6-minute walk), and fall frequencies were assessed at baseline, after 3 months and 6 months, and at 1-year follow-up. Multiple regression analyses with planned comparisons were carried out.

RESULTS

Eighty-nine participants were randomized to three groups initially; 71 completed the training and 47 were available at 1-year follow-up. DANCE/MEMORY showed a significant advantage compared to PHYS in DT costs of step time variability at fast walking (P=0.044). Training-specific gait adaptations were found on comparing DANCE and MEMORY: DANCE reduced step time at fast walking (P=0.007) and MEMORY reduced gait variability in DT and DT costs at preferred walking speed (both trend P=0.062). Global linear time effects showed improved gait (P<0.05), functional fitness (P<0.05), and reduced fall frequency (-77%, P<0.001). Only single-task fast walking, gait variability at preferred walking speed, and Short Physical Performance Battery were reduced at follow-up (all P<0.05 or trend).

CONCLUSION

Long-term multicomponent cognitive-physical and exclusive physical training programs demonstrated similar potential to counteract age-related decline in physical functioning.

Brain activity during walking: A systematic review

BACKGROUND

This systematic review provides an overview of the literature deducing information about brain activation during (1) imagined walking using MRI/fMRI or (2) during real walking using measurement systems as fNIRS, EEG and PET.

METHODS

Three independent reviewers undertook an electronic database research browsing six databases. The search request consisted of three search fields. The first field comprised common methods to evaluate brain activity. The second search field comprised synonyms for brain responses to movements. The third search field comprised synonyms for walking.

RESULTS

48 of an initial yield of 1832 papers were reviewed. We found differences in cortical activity regarding young vs. old individuals, physically fit vs. physically unfit cohorts, healthy people vs. patients with neurological diseases, and between simple and complex walking tasks.

CONCLUSIONS

We summarize that the dimension of brain activity in different brain areas during walking is highly sensitive to task complexity, age and pathologies supporting previous assumptions underpinning the significance of cortical control. Many compensation mechanisms reflect the brain's plasticity which ensures stable walking.

Episodic memory and executive function impairments in non-demented older adults: which are the respective and combined effects on gait performances?

Gait control depends in part on cognition. This study aims to examine the separate and combined effects of episodic memory and executive function impairments on the mean value and the coefficient of variation (CoV) of stride time among non-demented older community dwellers. Based on a cross-sectional design, 1458 older community dwellers without dementia (70.6 ± 4.9 years; 49.2 % female) were recruited and separated into cognitively healthy individuals (CHI) and individuals with cognitive impairment. A score ≤5/6 on the Short Mini-Mental State Examination defined episodic memory impairment. Impaired executive function was defined by errors on the clock-drawing test. Mean value and CoV of stride time were measured by the GAITRite® system. A total of 517 participants (35.5 %) had cognitive impairment in at least one cognitive domain. Participants with memory impairment (P = 0.006) and those with combined cognitive impairments (P < 0.001) had greater (i.e., worse gait performance) mean value of stride time (P = 0.006) compared to CHI. Participants with combined cognitive impairment had a greater CoV of stride time (i.e., worse gait performance) compared to CHI (P = 0.004) and to those with separate memory impairment (P = 0.037). Among participants with combined cognitive impairments, mean value and CoV of stride time had the highest effect size (respectively, effect size = 0.49 [95 % confidence interval (CI) 0.27;0.71] and effect size = 0.40 [95 %CI 0.18;0.62]). Participants with episodic memory or executive impairments had a greater mean value and CoV of stride time compared to those with no cognitive impairment. Combined episodic memory and executive impairments exceeded the sum of separate impairments on gait performances, suggesting a complex interplay going beyond a simple additive effect.

Respective and combined effects of impairments in sensorimotor systems and cognition on gait performance: a population-based cross-sectional study

Background

Respective and combined effects of impairments in sensorimotor systems and cognition on gait performance have not been fully studied. This study aims to describe the respective effects of impairments in muscle strength, distance vision, lower-limb proprioception and cognition on the Timed Up & Go (TUG) scores (i.e., performed TUG [pTUG], imagined TUG [iTUG] and the time difference between these two tests [delta TUG]) in older community-dwellers; and to examine their combined effects on TUG scores.

Methods

Based on a cross-sectional design, 1792 community-dwellers (70.2±4.8 years; 53.6% female) were recruited. Gait performance was assessed using pTUG, iTUG and delta TUG. Participants were divided into healthy individuals and 15 subgroups of individuals according to the presence of impairment in one or more subsystems involved in gait control (i.e., muscle strength and/or distance vision and/or lower-limb proprioception and/or cognition [episodic memory and executive performance]). Impairment in muscle strength, distance vision and lower-limb proprioception was defined as being in the lowest tertile of performance. Impairment in cognition was defined as abnormal episodic memory and executive tests.

Results

A total of 191 (10.7%) exhibited impairment in muscle strength, 188 (10.5%) in distance vision, 302 (16.9%) in lower-limb proprioception, and 42 (2.3%) in cognition. Linear regressions showed that cognitive impairment as well as dual combinations of impairments were associated with increased pTUG (P<0.02). Impairment in lower-limb proprioception was associated with decreased iTUG (P=0.015). All combinations of impairments, except those including muscle strength and the combinations of the 4 subsystems, were associated with increased delta TUG (P<0.04).

Conclusion

Cognitive integrity is central for efficient gait control and stability, whereas lower-limb proprioception seems to be central for gait imagery.

The association of brain structure with gait velocity in older adults: a quantitative volumetric analysis of brain MRI

INTRODUCTION

While cortical processes play an important role in controlling locomotion, the underlying structural brain changes associated with slowing of gait in aging are not yet fully established. Our study aimed to examine the relationship between cortical gray matter volume (GM), white matter volume (WM), ventricular volume (VV), hippocampal and hippocampal subfield volumes, and gait velocity in older adults free of dementia.

METHODS

Gait and cognitive performance was tested in 112 community-residing adults, age 70 years and over, participating in the Einstein Aging Study. Gait velocity (cm/s) was obtained using an instrumented walkway. Volumetric MRI measures were estimated using a FreeSurfer software. We examined the cross-sectional relationship of GM, WM, VV, and hippocampal total and subfield volumes and gait velocity using linear regression models. In complementary models, the effect of memory performance on the relationship between gait velocity and regional volumes was evaluated.

RESULTS

Slower gait velocity was associated with smaller cortical GM and total hippocampal volumes. There was no association between gait velocity and WM or VV. Among hippocampal subfields, only smaller presubiculum volume was significantly associated with decrease in gait velocity. Addition of the memory performance to the models attenuated the association between gait velocity and all volumetric measures.

CONCLUSIONS

Our findings indicate that total GM and hippocampal volumes as well as specific hippocampal subfield volumes are inversely associated with locomotor function. These associations are probably affected by cognitive status of study population.

Longitudinal assessment of neuropsychological and temporal/spatial gait characteristics of elderly fallers: taking it all in stride

Gait abnormalities are linked to cognitive decline and an increased fall risk within older adults. The present study addressed gaps from cross-sectional studies in the literature by longitudinally examining the interplay between temporal and spatial aspects of gait, cognitive function, age, and lower-extremity strength in elderly “fallers” and “non-fallers”. Gait characteristics, neuropsychological and physical test performance were examined at two time points spaced a year apart in cognitively intact individuals aged 60 and older (N = 416). Mixed-model repeated-measure ANCOVAs examined temporal (step time) and spatial (stride length) gait characteristics during a simple and cognitive-load walking task in fallers as compared to non-fallers. Fallers consistently demonstrated significant alterations in spatial, but not temporal, aspects of gait as compared to non-fallers during both walking tasks. Step time became slower as stride length shortened amongst all participants during the dual task. Shorter strides and slower step times during the dual task were both predicted by worse executive attention/processing speed performance. In summary, divided attention significantly impacts spatial aspects of gait in “fallers”, suggesting stride length changes may precede declines in other neuropsychological and gait characteristics, thereby selectively increasing fall risk. Our results indicate that multimodal intervention approaches that integrate physical and cognitive remediation strategies may increase the effectiveness of fall risk interventions.

Comparison of "Word" vs. "Picture" Version of the Free and Cued Selective Reminding Test (FCSRT) in Older Adults

Background

This study examined the psychometric relationship between the Word and Picture versions of the Free and Cued Selective Reminding Test (FCSRT) and developed an equation for score conversion.

Methods

One hundred and eight-seven participants were administered the FCSRT-Picture and FCSRT-Word on two visits using a randomized counterbalanced design.

Results

Participants had a mean age of 82.1 (standard deviation or SD = 5.4) and mean education of 14.5 (SD = 3.3) years. Mean FCSRT-Picture Free Recall score (mean 33.0 years, range: 17–44 years) was 7.9 points higher than the Word score (mean 25.1 years, range: 3–43 years). The Picture and Word FCSRT correlations for Free Recall and Total Recall were r = 0.56, P < .01 and r = 0.46, P < .01, respectively.

Discussion

The Picture and Word versions of the FCSRT were moderately associated in a sample of cognitively normal older adults. The score mean differences and variability between FCSRT-Picture and FCSRT-Word indicate that their scores should not be considered equivalent.

Hippocampal volume, early cognitive decline and gait variability: which association?

BACKGROUND

In contrast to its prominent function in cognition, the involvement of the hippocampus in gait control is still a matter of debate. The present study aimed to examine the association of the hippocampal volume with mean values and coefficients of variation (CoV) of spatio-temporal gait parameters among cognitively healthy individuals (CHI) and patients with mild cognitive impairment (MCI).

METHODS

A total of 90 individuals (47 CHI with a mean age of 69.7±3.6years and 48.9% women, and 43 MCI individuals with a mean age of 70.2±3.7years and 62.8% women) were included in this cross-sectional study. The hippocampal volume was quantified from a three-dimensional T1-weighted MRI using semi-automated software. Mean values and CoV of stride time, swing time and stride width were measured at self-selected pace with a 10m electronic portable walkway (GAITRite®). Age, gender, body mass index, number of drugs daily taken, Mini-Mental State Examination (MMSE) score, history of falls, walking speed and white matter signal-intensity abnormality scoring with Manolio scale were used as covariates.

RESULTS

Patients with MCI had a lower MMSE score (P<0.001), a higher CoV of stride time (P=0.013) and a lower hippocampal volume (P=0.007) compared with CHI. Multiple linear regression models showed that CoV of stride time was specifically associated with higher hippocampal volume among CHI (P<0.05) but not among patients with MCI (P>0.650).

CONCLUSIONS

Our findings revealed a positive association between a greater (i.e., better morphological structure) hippocampal volume and a greater (i.e., worse performance) stride time variability among CHI, but not among MCI individuals.

The motor signature of mild cognitive impairment: results from the gait and brain study

BACKGROUND

Early motor changes associated with aging predict cognitive decline, which suggests that a "motor signature" can be detected in predementia states. In line with previous research, we aim to demonstrate that individuals with mild cognitive impairment (MCI) have a distinct motor signature, and specifically, that dual-task gait can be a tool to distinguish amnestic (a-MCI) from nonamnestic MCI.

METHODS

Older adults with MCI and controls from the "Gait and Brain Study" were assessed with neurocognitive tests to assess cognitive performance and with an electronic gait mat to record temporal and spatial gait parameters. Mean gait velocity and stride time variability were evaluated under simple and three separate dual-task conditions. The relationship between cognitive groups (a-MCI vs nonamnestic MCI) and gait parameters was evaluated with linear regression models and adjusted for confounders.

RESULTS

Ninety-nine older participants, 64 MCI (mean age 76.3±7.1 years; 50% female), and 35 controls (mean age 70.4±3.9 years; 82.9% female) were included. Forty-two participants were a-MCI and 22 were nonamnestic MCI. Multivariable linear regression (adjusted for age, sex, physical activity level, comorbidities, and executive function) showed that a-MCI was significantly associated with slower gait and higher dual-task cost under dual-task conditions.

CONCLUSION

Participants with a-MCI, specifically with episodic memory impairment, had poor gait performance, particularly under dual tasking. Our findings suggest that dual-task assessment can help to differentiate MCI subtyping, revealing a motor signature in MCI.

Association between gait variability and brain ventricle attributes: a brain mapping study

BACKGROUND

It remains unknown which brain regions are involved in the maintenance of gait dynamic stability in older adults, as characterized by a low stride time variability. Expansion of lateral cerebral ventricles is an indirect marker of adjacent brain tissue volume. The purpose of this study was to examine the association between stride time variability and the volume of sub-regions of the lateral cerebral ventricles among older community-dwellers.

METHODS

One-hundred-fifteen participants free of hydrocephalus from the GAIT study (mean, 70.4±4.4years; 43.5% female) were included in this analysis. Stride time variability was measured at self-selected pace with a 10m electronic portable walkway (GAITRite). Participants were separated into 3 groups based on tertiles of stride time variability (i.e., <2.0%; 2.0-2.8%; >2.8%). Brain ventricle sub-volumes were quantified from three-dimensional T1-weighted MRI using semi-automated software. Age, gender, Cumulative Illness Rating Scale for Geriatrics, Mini-Mental State Examination, Go-NoGo, brain vascular burden, 4-item Geriatric Depression Scale, psychoactive drugs, vision, proprioception, body mass index, muscular strength and gait velocity were used as covariates.

RESULTS

Participants with the highest (i.e., worst) tertile of stride time variability exhibited larger temporal horns than those with the lowest (P=0.030) and intermediate tertiles (P=0.028). They also had larger middle portions of ventricular bodies than those with the intermediate tertile (P=0.018). Larger temporal horns were associated with increase in stride time variability (adjusted β=0.86, P=0.005), specifically with the highest tertile of stride time variability (adjusted OR=2.45, P=0.044).

CONCLUSIONS

Higher stride time variability was associated with larger temporal horns in older community-dwellers. Addressing focal neuronal losses in temporal lobes may represent an important strategy to prevent gait instability.

Motor phenotype of decline in cognitive performance among community-dwellers without dementia: population-based study and meta-analysis

Background

Decline in cognitive performance is associated with gait deterioration. Our objectives were: 1) to determine, from an original study in older community-dwellers without diagnosis of dementia, which gait parameters, among slower gait speed, higher stride time variability (STV) and Timed Up & Go test (TUG) delta time, were most strongly associated with lower performance in two cognitive domains (i.e., episodic memory and executive function); and 2) to quantitatively synthesize, with a systematic review and meta-analysis, the association between gait performance and cognitive decline (i.e., mild cognitive impairment (MCI) and dementia).

Methods

Based on a cross-sectional design, 934 older community-dwellers without dementia (mean±standard deviation, 70.3±4.9years; 52.1% female) were recruited. A score at 5 on the Short Mini-Mental State Examination defined low episodic memory performance. Low executive performance was defined by clock-drawing test errors. STV and gait speed were measured using GAITRite system. TUG delta time was calculated as the difference between the times needed to perform and to imagine the TUG. Then, a systematic Medline search was conducted in November 2013 using the Medical Subject Heading terms “Delirium,” “Dementia,” “Amnestic,” “Cognitive disorders” combined with “Gait” OR “Gait disorders, Neurologic” and “Variability.”

Findings

A total of 294 (31.5%) participants presented decline in cognitive performance. Higher STV, higher TUG delta time, and slower gait speed were associated with decline in episodic memory and executive performances (all P-values <0.001). The highest magnitude of association was found for higher STV (effect size  =  −0.74 [95% Confidence Interval (CI): −1.05;−0.43], among participants combining of decline in episodic memory and in executive performances). Meta-analysis underscored that higher STV represented a gait biomarker in patients with MCI (effect size  =  0.48 [95% CI: 0.30;0.65]) and dementia (effect size  = 1.06 [95% CI: 0.40;1.72]).

Conclusion

Higher STV appears to be a motor phenotype of cognitive decline.

Cognitive contributions to gait and falls: evidence and implications

Dementia and gait impairments often coexist in older adults and patients with neurodegenerative disease. Both conditions represent independent risk factors for falls. The relationship between cognitive function and gait has recently received increasing attention. Gait is no longer considered merely automated motor activity but rather an activity that requires executive function and attention as well as judgment of external and internal cues. In this review, we intend to: (1) summarize and synthesize the experimental, neuropsychological, and neuroimaging evidence that supports the role played by cognition in the control of gait; and (2) briefly discuss the implications deriving from the interplay between cognition and gait. In recent years, the dual task paradigm has been widely used as an experimental method to explore the interplay between gait and cognition. Several neuropsychological investigations have also demonstrated that walking relies on the use of several cognitive domains, including executive-attentional function, visuospatial abilities, and even memory resources. A number of morphological and functional neuroimaging studies have offered additional evidence supporting the relationship between gait and cognitive resources. Based on the findings from 3 lines of studies, it appears that a growing body of evidence indicates a pivotal role of cognition in gait control and fall prevention. The interplay between higher-order neural function and gait has a number of clinical implications, ranging from integrated assessment tools to possible innovative lines of interventions, including cognitive therapy for falls prevention on one hand and walking program for reducing dementia risk on the other.

Higher step length variability indicates lower gray matter integrity of selected regions in older adults

Step length variability (SLV) increases with age in those without overt neurologic disease, is higher in neurologic patients, is associated with falls, and predicts dementia. Whether higher SLV in older adults without neurologic disease indicates presence of neurologic abnormalities is unknown. Our objective was to identify whether SLV in older adults without overt disease is associated with findings from multimodal neuroimaging. A well-characterized cohort of 265 adults (79-90 years) was concurrently assessed by gait mat, magnetic resonance imaging with diffusion tensor, and neurological exam. Linear regression models adjusted for gait speed, demographic, health, and functional covariates assessed associations of MRI measures (gray matter volume, white matter hyperintensity volume, mean diffusivity, fractional anisotropy) with SLV. Regional distribution of associations was assessed by sparse partial least squares analyses. Higher SLV (mean: 8.4, SD: 3.3) was significantly associated with older age, slower gait speed, and poorer executive function and also with lower gray matter integrity measured by mean diffusivity (standardized beta=0.16; p=0.02). Associations between SLV and gray matter integrity were strongest for the hippocampus and anterior cingulate gyrus (both β=0.18) as compared to other regions. Associations of SLV with other neuroimaging markers were not significant. Lower integrity of normal-appearing gray matter may underlie higher SLV in older adults. Our results highlighted the hippocampus and anterior cingulate gyrus, regions involved in memory and executive function. These findings support previous research indicating a role for cognitive function in motor control. Higher SLV may indicate focal neuropathology in those without diagnosed neurologic disease.