Gait dysfunction in mild cognitive impairment syndromes

Effects of white matter lesions on trunk stability during dual-task walking among older adults with mild cognitive impairment

The linkage between gait and cognition has been shown in cases of white matter lesion (WML) that affect gait in older adults. Dual-task walking is believed to be cognitively demanding and to alter trunk movement, and gait impairment in people with mild cognitive impairment (MCI) is highlighted under this condition. However, the association between dual-task walking and structural changes in the brain, particularly with WML, in people with MCI is still unclear. The aim of this study was to examine the association between trunk stability during dual-task walking and WML in 560 older adults with MCI. We measured magnetic resonance imaging (MRI) and gait variables. Gait variables included harmonic ratio in vertical, mediolateral, and anteroposterior directions, analyzed using a tri-axial accelerometer attached to the lower trunk. Walking conditions were normal walking and dual-task walking (counting backwards while walking) conditions. Demographical data and brain atrophy were measured as covariates. Subjects were classified into non-severe WML (n = 451, mean age = 73.2 years) and severe WML (n = 109, mean age = 75.9 years) groups. Linear mixed-effects model analysis controlled for covariates showed dual-task-related changes in all harmonic ratios associated with WML (p < 0.05). Even after adjustment for executive function, harmonic ratio in the mediolateral direction was significantly associated with WML (p < 0.05). Our findings revealed that WMLs were associated with trunk stability in dual-task walking. Further studies are required to investigate the neural basis for deficits in gait ability among MCI subjects.

Neurological Gait Abnormalities Moderate the Functional Brain Signature of the Posture First Hypothesis

The posture first hypothesis suggests that under dual-task walking conditions older adults prioritize gait over cognitive task performance. Functional neural confirmation of this hypothesis, however, is lacking. Herein, we determined the functional neural correlates of the posture first hypothesis and hypothesized that the presence of neurological gait abnormalities (NGA) would moderate associations between brain activations, gait and cognitive performance. Using functional near-infrared spectroscopy we assessed changes in oxygenated hemoglobin levels in the pre-frontal cortex (PFC) during normal walk and walk while talk (WWT) conditions in a large cohort of non-demented older adults (n = 236; age = 75.5 ± 6.49 years; female = 51.7 %). NGA were defined as central (due to brain diseases) or peripheral (neuropathic gait) following a standardized neurological examination protocol. Double dissociations between brain activations and behavior emerged as a function of NGA. Higher oxygenation levels during WWT were related to better cognitive performance (estimate = 0.145; p < 0.001) but slower gait velocity (estimate = -6.336, p < 0.05) among normals. In contrast, higher oxygenation levels during WWT among individuals with peripheral NGA were associated with worse cognitive performance (estimate = -0.355; p < 0.001) but faster gait velocity (estimate = 14.855; p < 0.05). Increased activation in the PFC during locomotion may have a compensatory function that is designed to support gait among individuals with peripheral NGA.

Examining links between anxiety, reinvestment and walking when talking by older adults during adaptive gait

Falls by older adults often result in reduced quality of life and debilitating fear of further falls. Stopping walking when talking (SWWT) is a significant predictor of future falls by older adults and is thought to reflect age-related increases in attentional demands of walking. We examine whether SWWT is associated with use of explicit movement cues during locomotion, and evaluate if conscious control (i.e. movement specific reinvestment) is causally linked to fall-related anxiety during a complex walking task. We observed whether twenty-four older adults stopped walking when talking when asked a question during an adaptive gait task. After certain trials, participants completed a visuospatial recall task regarding walkway features, or answered questions about their movements during the walk. In a subsequent experimental condition, participants completed the walking task under conditions of raised postural threat. Compared to a control group, participants who SWWT reported higher scores for aspects of reinvestment relating to conscious motor processing but not movement self-consciousness. The higher scores for conscious motor processing were preserved when scores representing cognitive function were included as a covariate. There were no group differences in measures of general cognitive function, visuospatial working memory or balance confidence. However, the SWWT group reported higher scores on a test of external awareness when walking, indicating allocation of attention away from task-relevant environmental features. Under conditions of increased threat, participants self-reported significantly greater state anxiety and reinvestment and displayed more accurate responses about their movements during the task. SWWT is not associated solely with age-related cognitive decline or generic increases in age-related attentional demands of walking. SWWT may be caused by competition for phonological resources of working memory associated with consciously processing motor actions and appears to be causally linked with fall-related anxiety and increased vigilance.

Use of High-Frequency In-Home Monitoring Data May Reduce Sample Sizes Needed in Clinical Trials

Background

Trials in Alzheimer’s disease are increasingly focusing on prevention in asymptomatic individuals. This poses a challenge in examining treatment effects since currently available approaches are often unable to detect cognitive and functional changes among asymptomatic individuals. Resultant small effect sizes require large sample sizes using biomarkers or secondary measures for randomized controlled trials (RCTs). Better assessment approaches and outcomes capable of capturing subtle changes during asymptomatic disease stages are needed.

Objective

We aimed to develop a new approach to track changes in functional outcomes by using individual-specific distributions (as opposed to group-norms) of unobtrusive continuously monitored in-home data. Our objective was to compare sample sizes required to achieve sufficient power to detect prevention trial effects in trajectories of outcomes in two scenarios: (1) annually assessed neuropsychological test scores (a conventional approach), and (2) the likelihood of having subject-specific low performance thresholds, both modeled as a function of time.

Methods

One hundred nineteen cognitively intact subjects were enrolled and followed over 3 years in the Intelligent Systems for Assessing Aging Change (ISAAC) study. Using the difference in empirically identified time slopes between those who remained cognitively intact during follow-up (normal control, NC) and those who transitioned to mild cognitive impairment (MCI), we estimated comparative sample sizes required to achieve up to 80% statistical power over a range of effect sizes for detecting reductions in the difference in time slopes between NC and MCI incidence before transition.

Results

Sample size estimates indicated approximately 2000 subjects with a follow-up duration of 4 years would be needed to achieve a 30% effect size when the outcome is an annually assessed memory test score. When the outcome is likelihood of low walking speed defined using the individual-specific distributions of walking speed collected at baseline, 262 subjects are required. Similarly for computer use, 26 subjects are required.

Conclusions

Individual-specific thresholds of low functional performance based on high-frequency in-home monitoring data distinguish trajectories of MCI from NC and could substantially reduce sample sizes needed in dementia prevention RCTs.

Mild Cognitive Impairment, Slow Gait, and Risk of Disability: A Prospective Study

OBJECTIVES

Mild cognitive impairment (MCI) may be a risk for disability, and co-occurrence of slow gait (SG) and MCI may increase this risk.

DESIGN

Prospective study.

SETTING

General community.

PARTICIPANTS

The study included 3482 older adults (mean age: 71.4 years) without disability at baseline.

MEASUREMENTS

We collected information on demographic variables, measured gait speed and cognitive function to diagnose MCI at baseline. During the follow-up period, the incident disability was monitored. Participants were divided into groups without MCI and SG (control), with SG without MCI (SG), without SG and with MCI in single (sMCI) or multiple (mMCI) domains, and with SG and MCI in single (sMCI + SG) and multiple (mMCI + SG) domains.

RESULTS

During follow-up, 134 participants developed disability (mean follow-up: 29.4 months). The proportions of incident disability were higher in the MCI with SG, MCI, and SG groups, compared with the control group. SG [hazard ratio 2.27 (95% confidence interval: 1.38-3.73)], mMCI [2.56 (1.31-5.02)], sMCI + SG [2.46 (1.21-5.00)], and mMCI + SG [3.48 (1.79-6.76)] participants had risks for disability.

CONCLUSIONS

Co-occurrence of SG and MCI in multiple domains has a higher risk of disability than each condition alone.

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.

Review of information and communication technology devices for monitoring functional and cognitive decline in Alzheimer's disease clinical trials

Detecting and monitoring early cognitive impairment in Alzheimer's disease (AD) is a significant need in the field of AD therapeutics. Successful AD clinical trial designs have to overcome challenges related to the subtle nature of early cognitive changes. Continuous unobtrusive assessments using Information and Communication Technology (ICT) devices to capture markers of intra-individual change over time to assess cognitive and functional disability therefore offers significant benefits. We review the literature and provide an overview on randomized clinical trials in AD that use intelligent systems to monitor functional decline, as well as strengths, weaknesses, and future directions for the use of ICTs in a new generation of AD clinical trials.

Gait in drug naïve patients with de novo Parkinson's disease--altered but symmetric

BACKGROUND

Motor symptoms in Parkinson's disease (PD) are typically asymmetrical. Early stage of PD is characterised with a predominantly unilateral appearance of tremor, rigidity and bradykinesia, with or without axial involvement. Also, studies have demonstrated gait asymmetry in de novo drug naïve PD patients. Aim of this study was to investigate gait pattern, gait symmetry and gait variability in early phases of PD.

METHODS

The gait was measured in 40 de novo, drug naïve PD patients and 43 healthy control subjects (HC) while performing a simple walking task. Calculated parameters were cycle time (CT), stride length (SL) and swing time (ST), and their coefficients of variation (CV).

RESULTS

Considering gait parameters, PD patients and HC differed in terms of all parameters, except for the CV of CT. Analysis of gait symmetry, comparison between the gait patterns of the left and the right leg in PD patients revealed no difference for any of the assessed parameters. The majority of the gait parameters did not differ between left and right legs of HC.

CONCLUSIONS

It can be concluded that even gait was already altered in de novo drug naive PD patients, gait symmetry remained preserved. The SL was the most prominent parameter of altered gait in initial stages of PD patients, while the ST heralded postural asymmetry.

Gait speed and cognitive decline over 2 years in the Ibadan study of aging

BACKGROUND

The evidence suggesting that gait speed may represent a sensitive marker for cognitive decline in the elderly requires support from diverse racial groups.

OBJECTIVE

We investigated the relationship between gait speed and cognitive decline over 2 years in a community dwelling sample of elderly Africans.

METHODS

Data are from the Ibadan study of aging (ISA) conducted among a household multi-stage probability sample of 2149 Yoruba Nigerians aged 65 years or older. Gait speed was measured as the time taken to complete a 3 or 4m distance at normal walking speed. We assessed cognitive functions with a modified version of the 10-word learning list and delay recall test, and examined the relationship between baseline gait speed, as well as gait speed changes, and follow-up cognition using multiple linear regression and longitudinal analyses using random effects.

RESULTS

Approximately 71% of 1461 participants who were dementia free and who had their gait speed measured at baseline (2007) were successfully followed up in two waves (2008 and 2009). Along with increasing age, poor health and economic status, a slower baseline gait speed was independently associated with poorer follow-up cognition in both linear regression (1.2 words, 95% CI=0.48-2.0) and longitudinal analyses (0.8 words, 95% CI=0.44-1.2). Also, a greater change in gait speed between 2007 and 2009 was associated with the worst follow-up cognition (0.3 words, 95% CI=0.09-0.51).

CONCLUSION

The finding that a substantial change in gait speed was associated with reduced cognitive performance is of potential importance to efforts aimed at early identification of cognitive disorders in this population.

Functional mobility in a divided attention task in older adults with cognitive impairment

Motor disorders may occur in mild cognitive impairment (MCI) and at early stages of Alzheimer's disease (AD), particularly under divided attention conditions. We examined functional mobility in 104 older adults (42 with MCI, 26 with mild AD, and 36 cognitively healthy) using the Timed Up and Go test (TUG) under 4 experimental conditions: TUG single task, TUG plus a cognitive task, TUG plus a manual task, and TUG plus a cognitive and a manual task. Statistically significant differences in mean time of execution were found in all four experimental conditions when comparing MCI and controls (p < .001), and when comparing MCI and AD patients (p < .05). Receiver-operating characteristic curve analyses showed that all four testing conditions could differentiate the three groups (area under the curve > .8, p < .001 for MCI vs. controls; area under the curve > .7, p < .001 for MCI vs. AD). The authors conclude that functional motor deficits occurring in MCI can be assessed by the TUG test, in single or dual task modality.

Autonomous unobtrusive detection of mild cognitive impairment in older adults

The current diagnosis process of dementia is resulting in a high percentage of cases with delayed detection. To address this problem, in this paper, we explore the feasibility of autonomously detecting mild cognitive impairment (MCI) in the older adult population. We implement a signal processing approach equipped with a machine learning paradigm to process and analyze real-world data acquired using home-based unobtrusive sensing technologies. Using the sensor and clinical data pertaining to 97 subjects, acquired over an average period of three years, a number of measures associated with the subjects' walking speed and general activity in the home were calculated. Different time spans of these measures were used to generate feature vectors to train and test two machine learning algorithms namely support vector machines and random forests. We were able to autonomously detect MCI in older adults with an area under the ROC curve of 0.97 and an area under the precision-recall curve of 0.93 using a time window of 24 weeks. This study is of great significance since it can potentially assist in the early detection of cognitive impairment in older adults.

Dual task-related gait changes in patients with mild cognitive impairment

Mild cognitive impairment (MCI) entails a high risk of developing Alzheimer's dementia. In MCI patients gait impairment, which increases the risk of falls and institutionalization, is an early motor sign. A dualtask (DT) paradigm might improve the observation of this phenomenon. The aim of this study was to investigate motor-cognitive interference in a sample of MCI patients and a group of matched healthy controls submitted to DT conditions. To this end, three different cognitive tasks were used: counting backwards, short story recall and a phonemic fluency task. Overall, the patients, compared with the healthy participants, performed worse on the cognitive tasks and showed some degree of gait impairment. In the DT conditions, both groups showed significant gait disruption independently of the concomitant cognitive task. As regards cognitive performance, counting backwards worsened during dual tasking, while short story recall improved in both groups. Overall, our results suggest that the use of a DT paradigm does not improve the early detection of MCI. Our findings of enhanced story recall during walking might have interesting implications for rehabilitation of memory function.

At the interface of sensory and motor dysfunctions and Alzheimer's disease

Recent evidence indicates that sensory and motor changes may precede the cognitive symptoms of Alzheimer's disease (AD) by several years and may signify increased risk of developing AD. Traditionally, sensory and motor dysfunctions in aging and AD have been studied separately. To ascertain the evidence supporting the relationship between age-related changes in sensory and motor systems and the development of AD and to facilitate communication between several disciplines, the National Institute on Aging held an exploratory workshop titled "Sensory and Motor Dysfunctions in Aging and AD." The scientific sessions of the workshop focused on age-related and neuropathologic changes in the olfactory, visual, auditory, and motor systems, followed by extensive discussion and hypothesis generation related to the possible links among sensory, cognitive, and motor domains in aging and AD. Based on the data presented and discussed at this workshop, it is clear that sensory and motor regions of the central nervous system are affected by AD pathology and that interventions targeting amelioration of sensory-motor deficits in AD may enhance patient function as AD progresses.

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.

Gait velocity is an indicator of cognitive performance in healthy middle-aged adults

Psychomotor retardation, especially motor and cognitive slowing down, has been described many times in the elderly but to our knowledge, has never been examined in healthy middle-aged adults. The present study explores whether walking time may provide an early signal of cognitive performance, using 266 healthy adults ([18–65] years old, mean age: 45.7±12.9 years) who were also subdivided in 2 groups: under or over 50. Walking time (50 meters) and cognitive performances (mini-mental state examination, Benton Visual Retention Test and Rey Complex Figure) were assessed; total psychometric score was the sum of individual test scores. Analyses were controlled for age, gender, education level, height and weight. The mean psychometric scores were within the normal range. A substantial proportion of subjects exhibited low performance in some aspects of visuospatial memory, particularly in the older subset. In the total population, walking time was negatively correlated with all cognitive tests, particularly to total psychometric score (R = −0.817, p<0.0001); the unique contribution of walking time on all cognitive scores was very high (delta R-squared = 0.496). In the older subset, performances on walk and cognition were lower than in the younger subset. Total psychometric score showed the strongest correlation with walking time in the older subset (R = −0.867; p<0.001). In all subsets, walking time was the main explanatory variable of the total psychometric score (delta R-squared: ≤ 49 = 0.361; ≥50 = 0.613). These findings indicate that i) a significant proportion of adults without cognitive complaints exhibit low cognitive performance including visuospatial memory and longer walking time, ii) cognitive functioning is strongly correlated to walking time in healthy middle-aged adults, iii) gait velocity (GV) could be an indicator of cognitive performance in some important cognitive domains. These results warrant further investigation because such data may represent a marker for the detection of middle-aged adults who are at risk for further cognitive decline.

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.

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

BACKGROUND

Patients with Parkinson's disease (PD) suffer from a high fall risk. Previous approaches for evaluating fall risk are based on self-report or testing at a given time point and may, therefore, be insufficient to optimally capture fall risk. We tested, for the first time, whether metrics derived from 3 day continuous recordings are associated with fall risk in PD.

METHODS AND MATERIALS

107 patients (Hoehn & Yahr Stage: 2.6±0.7) wore a small, body-fixed sensor (3D accelerometer) on lower back for 3 days. Walking quantity (e.g., steps per 3-days) and quality (e.g., frequency-derived measures of gait variability) were determined. Subjects were classified as fallers or non-fallers based on fall history. Subjects were also followed for one year to evaluate predictors of the transition from non-faller to faller.

RESULTS

The 3 day acceleration derived measures were significantly different in fallers and non-fallers and were significantly correlated with previously validated measures of fall risk. Walking quantity was similar in the two groups. In contrast, the fallers walked with higher step-to-step variability, e.g., anterior-posterior width of the dominant frequency was larger (p = 0.012) in the fallers (0.78 ± 0.17 Hz) compared to the non-fallers (0.71 ± 0.07 Hz). Among subjects who reported no falls in the year prior to testing, sensor-derived measures predicted the time to first fall (p = 0.0034), whereas many traditional measures did not. Cox regression analysis showed that anterior-posterior width was significantly (p = 0.0039) associated with time to fall during the follow-up period, even after adjusting for traditional measures.

CONCLUSIONS/SIGNIFICANCE

These findings indicate that a body-fixed sensor worn continuously can evaluate fall risk in PD. This sensor-based approach was able to identify transition from non-faller to faller, whereas many traditional metrics were not successful. This approach may facilitate earlier detection of fall risk and may in the future, help reduce high costs associated with falls.

Mild cognitive impairment status and mobility performance: an analysis from the Boston RISE study

BACKGROUND

The prevalence of mild cognitive impairment (MCI) and mobility limitations is high among older adults. The aim of this study was to investigate the association between MCI status and both performance-based and self-report measures of mobility in community-dwelling older adults.

METHODS

An analysis was conducted on baseline data from the Boston Rehabilitative Impairment Study in the Elderly study, a cohort study of 430 primary care patients aged 65 or older. Neuropsychological tests identified participants with MCI and further subclassified those with impairment in memory domains (aMCI), nonmemory domains (naMCI), and multiple domains (mdMCI). Linear regression models were used to assess the association between MCI status and mobility performance in the Habitual Gait Speed, Figure of 8 Walk, Short Physical Performance Battery, and self-reported Late Life Function and Disability Instrument's Basic Lower Extremity and Advanced Lower Extremity function scales.

RESULTS

Participants had a mean age of 76.6 years, and 42% were characterized with MCI. Participants with MCI performed significantly worse than participants without MCI (No-MCI) on all performance and self-report measures (p < .01). All MCI subtypes performed significantly worse than No-MCI on all mobility measures (p < .05) except for aMCI versus No-MCI on the Figure of 8 Walk (p = .054) and Basic Lower Extremity (p = .11). Moreover, compared with aMCI, mdMCI manifested worse performance on the Figure of 8 Walk and Short Physical Performance Battery, and naMCI manifested worse performance on Short Physical Performance Battery and Basic Lower Extremity.

CONCLUSIONS

Among older community-dwelling primary care patients, performance on a broad range of mobility measures was worse among those with MCI, appearing poorest among those with nonmemory MCI.

Balance confidence and falls in nondemented essential tremor patients: the role of cognition

OBJECTIVES

To examine (1) the effect of cognitive ability on balance confidence and falls, (2) the relationship of balance confidence and falls with quantitative measures of gait, and (3) measures that predict falls, in people with essential tremor (ET).

DESIGN

Cross-sectional study.

SETTING

General community.

PARTICIPANTS

People with ET (n=132) and control subjects (n=48). People with ET were divided into 2 groups based on the median score on the Modified Mini-Mental State Examination: those with lower cognitive test scores (ET-LCS) and those with higher cognitive test scores (ET-HCS).

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Six-item Activities of Balance Confidence (ABC-6) Scale and falls in the previous year.

RESULTS

Participants with ET-LCS had lower ABC-6 scores and a greater number of falls than those with ET-HCS (P<.05 for all measures) or control subjects (P<.01 for all measures). Quantitative gait measures were significantly correlated with ABC-6 score and falls. Gait speed (P<.007) and ABC-6 score (P<.02) were significant predictors of falls. Receiver operating characteristic curve analysis revealed that gait speed <0.9m/s and ABC-6 score <51% were associated with moderate sensitivity and specificity in identifying fallers.

CONCLUSIONS

People with ET-LCS have impaired gait and report lower balance confidence and a higher number of falls than their counterparts (ET-HCS) and than control subjects. We have identified assessments that are easily administered (gait speed, ABC-6 Scale) and are associated with falls in ET.

Cognitive function and gait speed under normal and dual-task walking among older adults with mild cognitive impairment

Background

Gait ability and cognitive function are interrelated during both normal walking (NW) and dual-task walking (DTW), and gait ability is thus adversely affected by cognitive impairment in both situations. However, this association is insufficiently understood in people with mild cognitive impairment (MCI). Here, we conducted a study with MCI participants, to examine whether the association depends on walking conditions and MCI subtypes.

Methods

We classified 389 elderly adults into amnestic MCI (n = 191) and non-amnestic MCI (n = 198), assessed their cognitive functions, and administered gait experiments under NW and DTW conditions. Gait ability was defined as gait speed. Five aspects of cognitive function were assessed: processing speed, executive function, working memory, verbal memory, and visual memory.

Results

Regression analysis adjusted for covariates showed a significant association between cognitive functions and gait speed. Processing speed and executive function correlated with gait speed during both NW and DTW (p < .05). Gait speed during DTW was also significantly associated with working memory (p < .001). Visual memory was associated during NW and DTW, particularly for amnestic MCI participants (p < .05).

Conclusions

Our findings support the idea that the association between gait speed and cognitive function depends on walking condition and MCI subtypes. Additional studies are necessary to determine the neural basis for the disruption in gait control in older adults with MCI.

Age and CGG-repeat length are associated with neuromotor impairments in at-risk females with the FMR1 premutation

Recent studies report a higher risk of dementia and motor symptoms in females with the fragile X mental retardation 1 premutation (PM-carriers) than has hitherto been appreciated. Here, we use dual-task gait paradigms to identify potential markers of cognitive and motor decline in female PM-carriers. Spatiotemporal gait characteristics and variability of gait were assessed during single- and dual-task conditions in 28 female PM-carriers (mean age 41.32 ± 8.03 years) and 31 female controls with normal fragile X mental retardation 1 alleles (mean age 41.61 ± 8.30 years). Despite comparable gait characteristics at baseline, gait performance was significantly poorer for PM-carriers when performing concurrent working memory tasks (counting backwards by 3's or 7's) when compared with controls. Correlational analyses showed that low working memory capacity was significantly associated with dual-task interference for the gait domains of pace (speed, step length) and variability (step time, swing time) in PM-carriers. Multiple regression analyses further showed that the interaction between age and CGG repeat length was strongly predictive of gait variability during dual-task performance. These findings indicate for the first time that vulnerability in specific domains of gait control may act as sensitive surrogate markers of future decline in female PM-carriers.

Visually encoded working memory is closely associated with mobility in older adults

Previous research suggests that older adults' motor performance is associated with cognitive function. Although this has been reported especially for executive function, it is not yet clear for various types of working memory (WM). In fact, age-related decline in WM is more severe for faces than other types of visual objects. The present study focused on the relationship between diverse WM and two types of motor performance (mobility and manual dexterity), which are implicated in pathological decline. To measure diverse WM, we adopted N-back tasks using three distinct types of stimuli (numbers, locations, and faces). Mobility was measured with the timed up and go test and manual dexterity was measured with the Pegboard Test. Participants were community-dwelling older adults (age: mean 78.6 years). Comparisons of younger and older adults' N-back performances indicated that WM for faces is more sensitive to aging compared with WM for the other stimuli. Correlation analyses within the older group indicated that WM tasks mainly correlated with mobility, but less so with manual dexterity. Among the three types of WM, spatial WM and face WM had significant partial correlation coefficients with mobility after age and general cognitive decline were controlled. These results indicate that visually encoded WM is associated only with mobility, although general cognitive function is related to both motor abilities. The selective association between the visually encoded WM and mobility is discussed in terms of the interactive processes between executive processing and perceptual encoding, where dynamic visual processing for locomotion plays a role.

Spatial variability during gait initiation while dual tasking is increased in individuals with mild cognitive impairment

BACKGROUND

Gait initiation (GI) is a complex transition phase of gait that can induce postural instability. Gait impairment has been well documented in people with Alzheimer's disease, but it is still inconclusive in individuals with Mild Cognitive Impairment (MCI). Previous studies have usually investigated gait performance of cognitive impaired persons under steady state walking.

OBJECTIVE

This study aimed to examine spatiotemporal variability during GI under single- and dual-task conditions in people with and without MCI.

METHODS

Spatiotemporal stepping characteristics and variability under single- and dual-task conditions (counting backwards by 3s) were assessed in 30 older adults with MCI and 30 cognitively intact controls. Mean and coefficients of variation (COV) of swing time, step time, step length and step width were compared between the two groups.

RESULTS

Mixed-model repeated measures ANOVA revealed a significant Group x Walking condition interaction for COV of step length and step width (P<0.05). Post-hoc analysis revealed that variability for these measures were significantly larger in the MCI group compared with the control group under the dual-task condition (P<0.05).

CONCLUSIONS

Step length and step width variability is increased in people with MCI during GI, particularly in a condition involving a secondary cognitive task. These findings suggest that individuals with MCI have reduced balance control when undertaking a challenging walking task such as gait initiation, and this is exacerbated with an added cognitive task. Future studies should prospectively investigate the relationship between GI variability and fall risk in this population.

Behavioral and neural correlates of imagined walking and walking-while-talking in the elderly

Cognition is important for locomotion and gait decline increases the risk for morbidity, mortality, cognitive decline, and dementia. Yet, the neural correlates of gait are not well established, because most neuroimaging methods cannot image the brain during locomotion. Imagined gait protocols overcome this limitation. This study examined the behavioral and neural correlates of a new imagined gait protocol that involved imagined walking (iW), imagined talking (iT), and imagined walking-while-talking (iWWT). In Experiment 1, 82 cognitively-healthy older adults (M=80.45) walked (W), iW, walked while talking (WWT) and iWWT. Real and imagined walking task times were strongly correlated, particularly real and imagined dual-task times (WWT and iWWT). In Experiment 2, 33 cognitively-healthy older adults (M=73.03) iW, iT, and iWWT during functional magnetic resonance imaging. A multivariate Ordinal Trend (OrT) Covariance analysis identified a pattern of brain regions that: (1) varied as a function of imagery task difficulty (iW, iT and iWWT), (2) involved cerebellar, precuneus, supplementary motor and other prefrontal regions, and (3) were associated with kinesthetic imagery ratings and behavioral performance during actual WWT. This is the first study to compare the behavioral and neural correlates of imagined gait in single and dual-task situations, an issue that is particularly relevant to elderly populations. These initial findings encourage further research and development of this imagined gait protocol as a tool for improving gait and cognition among the elderly.

Performance variance on walking while talking tasks: theory, findings, and clinical implications

Dual tasks that involve walking and cognitive interference tests are commonly used in mobility assessments and interventions. However, factors that explain variance in dual-task performance costs are poorly understood. We, therefore, examined the moderating effects of two putative constructs, postural reserve and hazard estimate, on performance on a walking while talking paradigm. Participants were 285 non-demented older adults (mean age = 76.9 years; %female = 54.4). Postural reserve was operationalized as the presence or absence of clinical gait abnormalities. An empirical factor, based on measures of executive functions, served as a marker for hazard estimate. The moderation effects of postural reserve and hazard estimate on dual-task costs were examined via two-way interactions in a joint linear mixed effect model. Significant dual-task costs were observed for gait speed (95% CI = 30.814 to 39.121) and cognitive accuracy (95% CI = 6.568 to 13.607). High hazard estimate had a protective effect against decline in gait speed (95% CI = -8.372 to -0.151) and cognitive accuracy (95% CI = -8.372 to -0.680). Poor postural reserve was associated with reduced decline in gait speed (95% CI = -9.611 to -0.702) but did not moderate the decline in cognitive accuracy (95% CI = -3.016 to 4.559). Assessing postural reserve and hazard estimate can help improve mobility risk assessment procedures and interventions for individuals with cognitive and movement disorders.

Locomotion, cognition and influences of nutrition in ageing

Gait and cognitive impairments in older adults can reflect the simultaneous existence of two syndromes that affect certain brain substrates and pathologies. Nutritional deficiencies, which are extremely common among elderly population worldwide, have potential to impact the existence and rehabilitation of both syndromes. Gait and cognition are controlled by brain circuits which are vulnerable to multiple age-related pathologies such as vascular diseases, inflammation and dementias that may be caused or accentuated by poor nutrition or deficiencies that lead to cognitive, gait or combined cognitive and gait impairments. The following review aims to link gait and cognitive classifications and provide an overview of the potential impact of nutritional deficiencies on both neurological and gait dysfunctions. The identification of common modifiable risk factors, such as poor nutrition, may serve as an important preventative strategy to reduce cognitive and mobility impairments and moderate the growing burden of dementia and disability worldwide.

Walking while talking and falls in aging

BACKGROUND

While divided attention tasks are recognized as predictors of falls in older adults, a comprehensive examination of this association is lacking.

OBJECTIVE

We examined the validity of a 'walking while talking' (WWT) task for predicting falls.

METHODS

We studied the associations of 8 selected gait markers measured during WWT (individually as well as domains derived by factor analysis) with incident falls in 646 adults (mean age 79.9 years; 61% women) enrolled in an aging study who received quantitative gait assessments. Cox regressions adjusted for multiple potential confounders and normal-pace walking were used to examine the associations.

RESULTS

Over a mean follow-up of 2.6 years, 337 participants (52%) fell. Step length was the only individual WWT parameter that predicted falls [hazard ratio (HR) 0.98; p = 0.034]. Factor analysis identified 3 gait domains, of which only the pace factor predicted falls (HR 1.31; p = 0.002). Results remained robust after adjusting for multiple potential confounders and accounting for normal-pace walking.

CONCLUSIONS

WWT performance was a significant predictor of falls. Gait domains in WWT should be further studied to improve current fall risk assessments and to develop new interventions.

Subtle gait changes in patients with REM sleep behavior disorder

Many people with rapid eye movement (REM) sleep behavior disorder (RBD) have an underlying synucleinopathy, the most common of which is Lewy body disease. Identifying additional abnormal clinical features may help in identifying those at greater risk of evolving to a more severe syndrome. Because gait disorders are common in the synucleinopathies, early abnormalities in gait in those with RBD could help in identifying those at increased risk of developing overt parkinsonism and/or cognitive impairment. We identified 42 probable RBD subjects and 492 controls using the Mayo Sleep Questionnaire and assessed gait velocity, cadence, and stride dynamics with an automated gait analysis system. Cases and controls were similar in age (79.9 ± 4.7 and 80.1 ± 4.7, P = 0.74), Unified Parkinson's Disease Rating Scale Part III (UPDRS) score (3.3 ± 5.5 and 1.9 ± 4.1, P = 0.21) and Mini-Mental State Examination scores (27.2 ± 1.9 and 27.7 ± 1.6, P = 0.10). A diagnosis of probable RBD was associated with decreased velocity (-7.9 cm/s; 95% confidence interval [CI], -13.8 to -2.0; P < 0.01), cadence (-4.4 steps/min; 95% CI, -7.6 to -1.3; P < 0.01), significantly increased double limb support variability (30%; 95% CI, 6-60; P = 0.01), and greater stride time variability (29%; 95% CI, 2-63; P = 0.03) and swing time variability (46%; 95% CI, 15-84; P < 0.01). Probable RBD is associated with subtle gait changes prior to overt clinical parkinsonism. Diagnosis of probable RBD supplemented by gait analysis may help as a screening tool for disorders of α-synuclein.

Brain activation during dual-task walking and executive function among older adults with mild cognitive impairment: a fNIRS study

BACKGROUND AND AIMS

Dual-task walking (DTW) is thought to involve activation of the prefrontal cortex in healthy adults and to be affected by cognitive impairment. However, it is unclear whether prefrontal cortex activation is involved in DTW in older adults with mild cognitive impairment. This study examined brain activation during DTW among older adults with mild cognitive impairment using functional near-infrared spectroscopy.

METHODS

Sixteen older adults (aged 75.4 ± 7.2 years, women n = 6) performed gait experiments under normal walking and DTW conditions. We used a design with 60-s blocks consisting of a 10-s rest standing as pre-resting period, a 20-s walking task period, and a 30-s rest standing as post-resting period. Walking speed was measured during a 20-s walking task. Changes in oxy-hemoglobin were measured in the prefrontal area during gait experiments.

RESULTS

Walking speed was slower during DTW compared with normal walking (p < 0.001). The oxy-hemoglobin level during DTW was higher than during normal walking (p < 0.001) and was correlated with executive function, as measured by Stroop interference (p < 0.05).

CONCLUSION

Our findings indicate that DTW is associated with prefrontal activation among older adults with mild cognitive impairment. The brain activation during DTW was correlated with executive function. Additional studies are necessary to elucidate the effects of cognitive impairment on the association between prefrontal activity and walking under various conditions.

Cognitive motor interference during dual-task gait in essential tremor

BACKGROUND

Functional ambulation requires concurrent performance of motor and cognitive tasks, which may create interference (degraded performance) in either or both tasks. People with essential tremor (ET) demonstrate impairments in gait and cognitive function. In this study we examined the extent of interference between gait and cognition in people with ET and controls during dual-task gait.

METHODS

We tested 62 controls and 151 ET participants (age range: 72-102). ET participants were divided into two groups based on median score on the modified Mini Mental State Examination. Participants walked at their preferred speed, and performed a verbal fluency task while walking. We analyzed gait velocity, cadence, stride length, double support time, stride time, step width, step time difference, coefficient of variation (CV) of stride time and stride length.

RESULTS

Verbal fluency performance during gait was similar across groups (p=0.68). Velocity, cadence and stride length were lowest whereas step time difference (p=0.003), double support time (p=0.009), stride time (p=0.002) and stride time CV (p=0.007) were highest for ET participants with lower cognitive scores (ETp-LCS), compared with ET participants with higher cognitive scores (ETp-HCS) and controls. ETp-LCS demonstrated greatest interference for double support time (p=0.005), step time difference (p=0.013) and stride time coefficient of variation (p=0.03).

CONCLUSIONS

ETp-LCS demonstrated high levels of cognitive motor interference. Gait impairments during complex tasks may increase risk for falls for this subgroup and underscore the importance of clinical assessment of gait under simple and dual-task conditions.

RELATIONSHIP OF GAIT AND COGNITION IN THE ELDERLY

Gait and cognitive impairments in older adults mostly reflect the co-occurrence of two geriatric syndromes linked by common underlying brain substrates and pathologies. Gait control is predominately mediated by frontal subcortical circuits, which overlap with circuits controlling executive control and attention functions. These circuits are vulnerable to multiple age-related pathologies such as ischemia, inflammation, and neurodegeneration, which could ultimately cause cognitive, gait, or combined cognitive and gait impairments. The following review aims to describe various gait and cognitive classifications, gait based phenotypes, common underlying pathological processes, and provide a link between motor and cognitive impairments in an effort to predict the risk of dementia, as well as remediate impairments by applying appropriate interventions.

Timed limb coordination performance is associated with walking speed in healthy older adults: a cross-sectional exploratory study

Walking speed reflects quality of life, health status and physical function in older adults but interpreting measures of walking speed is affected by several confounders such as gender, age and height. Additionally, walking speed is influenced by neurologic conditions that impair limb coordination. In absence of defined pathology, it is less clear how varying levels of limb coordination influence walking speed. The purpose of this study was to examine the relationship between limb coordination and walking speed in older adults, controlling for effects of gender, age and height. Sixty-nine healthy, community-dwelling individuals over the age of 60 participated in the study. Participants completed a battery of timed upper and lower limb coordination tests. Normal and fast walking speed were measured over the inner six meters of a 10 m walkway. Correlation and regression analyses were used to examine the relationship between limb coordination performance and walking speed. Controlling for gender, age and height, variance in normal walking speed was accounted for by variance in pronation-supination performance (partial r = -0.396, partial r(2) = 0.16) and variance in fast walking speed was accounted for by variance in finger-to-nose performance (partial r = -0.356, partial r(2) = 0.13). The findings support our hypothesis that limb coordination performance would correlate with walking speed in healthy older adults. Moreover, limb coordination performance attenuated the effects of gender, age and height on walking speed. Limb coordination may be a modifiable determinant of walking speed in older adults.

An economic evaluation of resistance training and aerobic training versus balance and toning exercises in older adults with mild cognitive impairment

Background

Mild cognitive impairment (MCI) represents a critical window to intervene against dementia. Exercise training is a promising intervention strategy, but the efficiency (i.e., relationship of costs and consequences) of such types of training remains unknown. Thus, we estimated the incremental cost-effectiveness of resistance training or aerobic training compared with balance and tone exercises in terms of changes in executive cognitive function among senior women with probable MCI.

Methods

Economic evaluation conducted concurrently with a six-month three arm randomized controlled trial including eighty-six community dwelling women aged 70 to 80 years living in Vancouver, Canada. Participants received twice-weekly resistance training (n = 28), twice weekly aerobic training (n = 30) or twice-weekly balance and tone (control group) classes (n = 28) for 6 months. The primary outcome measure of the Exercise for Cognition and Everyday Living (EXCEL) study assessed executive cognitive function, a test of selective attention and conflict resolution (i.e., Stroop Test). We collected healthcare resource utilization costs over six months.

Results

Based on the bootstrapped estimates from our base case analysis, we found that both the aerobic training and resistance training interventions were less costly than twice weekly balance and tone classes. Compared with the balance and tone group, the resistance-training group had significantly improved performance on the Stroop Test (p = 0.04).

Conclusions

Resistance training and aerobic training result in health care cost saving and are more effective than balance and tone classes after only 6 months of intervention. Resistance training is a promising strategy to alter the trajectory of cognitive decline in seniors with MCI.

Trial Registration

ClinicalTrials.gov NCT00958867.

Geriatric syndromes--vascular disorders?

The term geriatric syndrome is used to characterize multifactorial clinical conditions among older people which are not subsumed readily into disease entities, but which nevertheless predispose older people to disability and death. Commonly included are frailty, dementia, delirium, incontinence, falls, and dizziness. Geriatric syndromes are common among older people: in a recent survey, 50% of those aged more than 65 had one or more of these conditions. Better methods for prevention and treatment are needed, but current strategies have lacked a coherent conceptual and diagnostic framework. Prevention and interventions need to be targeted at earlier ages, with geriatrics expertise needed in the definition and operationalization of these complex entities. In this review we consolidate evidence that vascular disorders, including vascular ageing and vascular diseases, are key etiological factors of geriatric syndromes. Identifying this vascular dimension would offer opportunities for more efficient preventive strategies and mandates earlier intervention, especially for women, among whom vascular disease is often expressed more insidiously than among men. This would entail a sensitization of the health care system to the systematic detection of the syndromes, which are currently underdiagnosed. Further disentangling of the mechanisms of vascular ageing may offer therapies for vascular diseases and geriatric syndromes alike.

Is gait variability reliable in older adults and Parkinson's disease? Towards an optimal testing protocol

BACKGROUND

Despite the widespread use of gait variability in research and clinical studies, testing protocols designed to optimise its reliability have not been established. This study evaluates the impact of testing protocol and pathology on the reliability of gait variability.

OBJECTIVE

To (i) estimate the reliability of gait variability during continuous and intermittent walking protocols in older adults and people with Parkinson's disease (PD), (ii) determine optimal number of steps for acceptable levels of reliability of gait variability and (iii) provide sample size estimates for use in clinical trials.

METHODS

Gait variability was measured twice, one week apart, in 27 older adults and 25 PD participants. Participants walked at their preferred pace during: (i) a continuous 2 min walk and (ii) 3 intermittent walks over a 12 m walkway. Gait variability was calculated as the within-person standard deviation for step velocity, length and width, and step, stance and swing duration.

RESULTS

Reliability of gait variability ranged from poor to excellent (intra class correlations .041-.860; relative limits of agreement 34-89%). Gait variability was more reliable during continuous walks. Control and PD participants demonstrated similar reliability. Increasing the number of steps improved reliability, with most improvement seen across the first 30 steps.

CONCLUSIONS

In this study, we identified testing protocols that improve the reliability of measuring gait variability. We recommend using a continuous walking protocol and to collect no fewer than 30 steps. Early PD does not appear to impact negatively on the reliability of gait variability.

White matter hyperintensity volume and impaired mobility among older adults

Gait speed is associated with multiple adverse outcomes of aging. White matter hyperintensities (WMH) on magnetic resonance imaging (MRI) have been associated with gait speed, though few studies have examined changes in gait speed over time in population-based studies comprising participants from diverse cultural backgrounds. The purpose of this study was to examine the association between a decline in gait speed and total and regional WMH volumes in a community-based study of aging. Participants (n = 701) underwent gait-speed measurement via a 4-m walk test at the time of initial enrollment and MRI at a second time interval (mean 4.7 [SD = 0.5] years apart). Logistic regression was used to examine the association between large WMH volume and regional WMH volume with gait speed <0.5 m/s (abnormal speed), and a transition to abnormal gait speed. Analyses were adjusted for demographic and clinical factors. Large WMH volume was associated with abnormal gait speed and a transition to abnormal gait speed between the two visits, but not after adjustment for modifiable vascular disease risk factors. Increased frontal lobe WMH volume was associated with abnormal gait speed and transition to abnormal gait speed, but not in adjusted models. WMH are associated with slowing of gait over time. Prevention of WMH presents a potential strategy for the prevention of gait speed decline.

Gait variability at fast-pace walking speed: a biomarker of mild cognitive impairment?

BACKGROUND

The interpretation of the increase in stride-to-stride variability of stride time (STV) regarding the evolution of cognitive deficits across the dementia spectrum is matter of debate.

OBJECTIVE

The aim of this study was to compare STV at usual and fast-pace walking speeds of MCI patients with that of cognitively healthy individuals (CHI) and Alzheimer's disease (AD) patients with mild dementia, while considering the effects of potential confounders.

METHODS

STV while walking at usual and fast-pace walking speeds was recorded with the GAITRite® system from 116 older adults (mean age 75.6±6.5 years; 55.2% female) divided into 3 groups according to their cognitive status (44 CHI, 39 MCI patients and 33 AD patients with mild dementia).

RESULTS

The full adjusted multiple linear regression models showed that high STV was associated with slow gait speed at usual-pace walking speed (P=0.002) and with the MCI status at fast-pace walking speed (P=0.015).

CONCLUSIONS

High STV at fast-pace walking speed was a specific gait disturbance of MCI patients in the sample of studied participants, and thus could be used in the future as a specific biomarker of MCI patients.

Gait parameter risk factors for falls under simple and dual task conditions in cognitively impaired older people

Impaired gait may contribute to the increased rate of falls in cognitively impaired older people. We investigated whether gait under simple and dual task conditions could predict falls in this group. The study sample consisted of 64 community dwelling older people with mild to moderate cognitive impairment. Participants walked at their preferred speed under three conditions: (a) simple walking, (b) walking while carrying a glass of water and (c) walking while counting backwards from 30. Spatiotemporal gait parameters were measured using the GAITRite(®) mat. Falls were recorded prospectively for 12months with the assistance of carers. Twenty-two (35%) people fell two or more times in the 12month follow-up period. There was a significant main effect of gait condition and a significant main effect of faller status for mean value measures (velocity, stride length, double support time and stride width) and for variability measures (swing time variability and stride length variability). Examination of individual gait parameters indicated that the multiple fallers walked more slowly, had shorter stride length, spent longer time in double support, had a wider support width and showed more variability in stride length and swing time (p<0.05). There was no significant interaction between gait condition and faller status for any of the gait variables. In conclusion, dual task activities adversely affect gait in cognitively impaired older people. Multiple fallers performed worse in each gait condition but the addition of a functional or cognitive secondary task provided no added benefit in discriminating fallers from non-fallers with cognitive impairment.