Gait and risk of falls associated with frontal cognitive functions at different stages of Alzheimer's disease

ABSTRACT

The decline in frontal cognitive functions contributes to alterations of gait and increases the risk of falls in patients with dementia, a category which included Alzheimer's disease (AD). The objective of the present study was to compare the gait parameters and the risk of falls among patients at different stages of AD, and to relate these variables with cognitive functions. This is a cross-sectional study with 23 patients with mild and moderate AD. The Clinical Dementia Rating was used to classify the dementia severity. The kinematic parameters of gait (cadence, stride length, and stride speed) were analyzed under two conditions: (a) single task (free gait) and (b) dual task (walking and counting down). The risk of falls was evaluated using the Timed Up-and-Go test. The frontal cognitive functions were evaluated using the Frontal Assessment Battery (FAB), the Clock Drawing Test (CDT) and the Symbol Search Subtest. The patients who were at the moderate stage suffered reduced performance in their stride length and stride speed in the single task and had made more counting errors in the dual task and still had a higher fall risk. Both the mild and the moderate patients exhibited significant decreases in stride length, stride speed and cadence in the dual task. Was detected a significant correlation between CDT, FAB, and stride speed in the dual task condition. We also found a significant correlation between subtest Similarities, FAB and cadence in the dual task condition. The dual task produced changes in the kinematic parameters of gait for the mild and moderate AD patients and the gait alterations are related to frontal cognitive functions, particularly executive functions.     

Association Between Gait and Dual Task With Cognitive Domains in Older People With Cognitive Impairment

The authors investigated whether impaired gait and dual-task performances are associated with specific cognitive domains among older people with preserved cognition (PC), mild cognitive impairment (MCI), and mild Alzheimer's disease (AD). The sample comprised 40 older adults with PC, 40 with MCI, and 38 with mild AD. The assessment consisted of gait (measured by 10-m walk test and Timed Up and Go Test [TUGT]), dual task (measured by TUGT associated with a cognitive-motor task of calling a phone number), and cognition (domains of the Addenbrooke Cognitive Examination–Revised and Frontal Assessment Battery [FAB]). For data analysis, the Pearson product-moment correlation and the backward stepwise linear regression were conducted. Language, fluency, and visuospatial domains predicted the 10-m walk test measure specifically in PC, MCI, and AD groups. Only the visuospatial domain was independently associated with the TUGT measure in the MCI and AD groups. FAB score, language domain, and FAB score and fluency domain were the strongest predictors for the isolated cognitive-motor task measure in the PC, MCI, and AD groups, respectively. The visuospatial domain was independently associated with the dual-task test measure in all 3 groups. The study findings demonstrate the influence of specific cognitive domains in daily mobility tasks in people with different cognitive profiles.     

Correlation between functional mobility and cognitive performance in older adults with cognitive impairment

Association between cognitive impairment and gait performance occurs in mild cognitive impairment (MCI) and Alzheimer‘s disease (AD), particularly under “divided attention” conditions, leading to a greater risk of falls. We studied 36 controls, 42 MCI, and 26 mild AD patients, using the Timed Up-and-Go test (TUG) under four conditions: TUG single – TUG1; TUG cognitive – TUG2; TUG manual –TUG3; TUG cognitive and manual – TUG4. Cognition was assessed using the MMSE, SKT, Exit25, and TMT (A and B). We found significant correlations between cognitive scores and TUG2 [r values (MMSE: –0.383, TMT-A: 0.430, TMT-B: 0.386, Exit25: 0.455, SKT: 0.563)] and TUG4 [(MMSE: –0.398, TMT-A: 0.384, TMT-B: 0.352,Exit25: 0.466, SKT: 0.525)] in the AD group, and between all TUG modalities and SKT in MCI and AD. Our results revealed that functional mobility impairment in cognitive dual tasks correlated to cognitive decline in AD patients and to attention and memory impairment in MCI.     

Dual-task costs of texting while walking forward and backward are greater for older adults than younger adults

Cognitive-motor dual-tasking involves concurrent performance of two tasks with distinct cognitive and motor demands and is associated with increased fall risk. In this hypothesis-driven study, younger (18–30 years, n = 24) and older (60–75 years, n = 26) adults completed six walking tasks in triplicate. Participants walked forward and backward along a GAITRite mat, in isolation or while performing a verbal fluency task. Verbal fluency tasks involved verbally listing or typing on a smartphone as many words as possible within a given category (e.g., clothes). Using repeated measures MANOVA models, we examined how age, method of fluency task (verbal or texting), and direction of walking altered dual-task performance. Given that tasks like texting and backward walking require greater cognitive resources than verbal and forward walking tasks, respectively, we hypothesized older adults would show higher dual-task costs (DTCs) than younger adults across different task types and walking directions, with degree of impairment more apparent in texting dual-task trials compared to verbal dual-task trials. We also hypothesized that both age groups would have greater DTCs while walking backward than while walking forward, regardless of task.Independent of age group, velocity and stride length were reduced for texting compared to the verbal task during both forward and backward walking; cadence and velocity were reduced while walking forward compared to walking backward for the texting task; and stride length was reduced for forward walking compared to backward walking during the verbal task. Younger adults performed better than older adults on all tasks with the most pronounced differences seen in velocity and stride length during forward-texting and backward-texting. Interaction effects for velocity and stride length while walking forward indicated younger adults performed better than older adults for the texting task but similarly during the verbal task. An interaction for cadence during the verbal task indicated younger adults performed better than older adults while walking backward but similarly while walking forward.In summary, older adults experienced greater gait decrement for all dual-task conditions. The greater declines in velocity and stride length in combination with cadence being stable suggest reductions in velocity during texting were due to shorter strides rather than a reduced rate of stepping. Contrary to our hypotheses, we found greater DTCs while walking forward rather than backward, which may be due to reduced gait performance during single-task backward walking; thus, further decrements with dual-tasking are unlikely. These findings underscore the need for further research investigating fall risk potential associated with texting and walking among aging populations and how interventions targeting stride length during dual-task circumstances may improve performance.     

Clock drawing performance and brain morphology in mild cognitive impairment and Alzheimer's disease

The Clock Drawing Test (CDT) is a widely used instrument in the neuropsychological assessment of Alzheimer's disease (AD). As CDT performance necessitates several cognitive functions (e.g., visuospatial and constructional abilities, executive functioning), an interaction of multiple brain regions is likely. Fifty-one subjects with mild cognitive impairment, 23 with AD and 15 healthy controls underwent high-resolution magnetic resonance imaging. Optimized voxel-based morphometry (VBM) was performed to investigate the putative association between CDT performance and gray matter (GM) density throughout the entire brain. In the first step of analysis (p<.001, uncorrected), VBM revealed a reduced GM density in numerous cortical (temporal lobe, frontal lobe, parietal lobe, cerebellum) and subcortical (thalamus, basal ganglia) brain regions to be associated with poorer CDT performance. When corrected for multiple comparisons (p<.01), the associations remained significant predominantly in the left temporal and--less pronounced--the right temporal lobe. VBM demonstrated CDT performance to depend on the integrity of widely distributed cortical and subcortical areas in both brain hemispheres with accentuation in the left-sided temporal lobe region.     

Speed influences on the scaling behavior of gait cycle fluctuations during treadmill running

The current study examined the temporal structure of gait cycle fluctuations in running. Participants ran at 80%, 90%, 100%, 110% and 120% of preferred running speed for 8min trials. Kinematic and kinetic gait cycle variables were generated from ground reaction force data. Mean, SD and CV of the kinematic and kinetic variables changed linearly with speed, whereas U-shaped functions were found for the scaling exponent alpha in 5 of the 8 variables investigated. Our findings reveal that long range correlations are present in both kinetic and kinematic variables of the gait cycle. The dependent structure of the stride interval is reduced at preferred running speed and this is hypothesized to be related to the enhanced stability and flexibility of this gait speed.     

Influence of cognitive and motor tasks using smartphone during gait: EMG and gait performance analysis – Dual-task study

Previous studies reported changes in spatiotemporal gait parameters during dual-task performance while walking using a smartphone compared to walking without a smartphone. However, studies that assess muscle activity while walking and simultaneously performing smartphone tasks are scarce. So, this study aimed to assess the effects of motor and cognitive tasks using a smartphone while simultaneously performing gait on muscle activity and gait spatiotemporal parameters in healthy young adults. Thirty young adults (22.83 ± 3.92 years) performed five tasks: walking without a smartphone (single-task, ST); typing on a smartphone keyboard in a sitting position (secondary motor single-task); performing a cognitive task on a smartphone in a sitting position (cognitive single-task); walking while typing on a smartphone keyboard (motor dual-task, mot-DT) and walking while performing a cognitive task on a smartphone (cognitive dual-task, cog-DT). Gait speed, stride length, stride width and cycle time were collected using an optical motion capture system coupled with two force plates. Muscle activity was recorded using surface electromyographic signals from bilateral biceps femoris, rectus femoris, tibialis anterior, gastrocnemius medialis, gastrocnemius lateralis, gluteus maximus and lumbar erector spinae. Results showed a decrease in stride length and gait speed from the single-task to cog-DT and mot-DT (p < 0.05). On the other hand, muscle activity increased in most muscles analyzed from single- to dual-task conditions (p < 0.05). In conclusion, performing a cognitive or motor task using a smartphone while walking promote a decline in spatiotemporal gait parameters performance and change muscle activity pattern compared to normal walking.     

Biomechanical motor patterns in normal walking

Motor patterns in normal human gait are evident in several biomechanical and EMG analyses over the stride period. Some of these patterns are invariant over the stride period with changes of cadence, whole others are closely correlated with speed changes. The findings for slow, natural, and fast walking are summarized: 1. Joint angle patterns over the stride period are quite invariant, and do not change with cadence; 2. Moment of force patterns at the ankle are least variable and quite consistent at all speeds; 3. A recently defined support moment is quite consistent at all speeds. 4. Moments at the knee and hip are highly variable at all cadences but decrease their variability as cadence increases; 5. Mechanical power patterns at all joints show consistent timing over the stride period; 6. EMG profiles of 5 muscles show consistent timing over the stride, but the amplitude increases as walking speed increases. Arguments are presented to support the concept that walking speed is largely controlled by gain and that the timing of the motor patterns, which is extremely tightly synchronized with the anatomical position, is under major afferent control.     

A note on modulations and structuring of locomotion in children and adults

The aim of this study was to investigate the modulations of locomotion induced by a rhythmic cognitive task (counting one's steps). Subjects (6- and 8-year-olds and adults) were requested to walk freely, and then to walk while counting their steps. Here a decrease in cadence values was observed in children only, with quasi-total repercussions on velocity at the age of 6 only. The spatiotemporal structuring of locomotion described here is already present at 6 years of age and is not altered in the step-counting situation: strong links were observed between cadence and velocity, and between stride length and velocity, and weak links between cadence and stride length.     

A Note on Modulations and Structuring of Locomotion in Children and Adults

The aim of this study was to investigate the modulations of locomotion induced by a rhythmic cognitive task (counting one’s steps). Subjects (6-and 8-year-olds and adults) were requested to walk freely, and then to walk while counting their steps. Here a decrease in cadence values was observed in children only, with quasi-total repercussions on velocity at the age of 6 only. The spatiotemporal structuring of locomotion described here is already present at 6 years of age and is not altered in the step-counting situation: strong links were observed between cadence and velocity, and between stride length and velocity, and weak links between cadence and stride length.     

Biomechanical Motor Patterns in Normal Walking

Motor patterns in normal human gait are evident in several biomechanical and EMG analyses over the stride period. Some of these patterns are invariant over the stride period with changes of cadence, while others are closely correlated with speed changes. The findings for slow, natural, and fast walking are summarized: 1. Joint angle patterns over the stride period are quite invariant, and do not change with cadence;

2. Moment of force patterns at the ankle are least variable and quite consistent at all speeds;

3. A recently defined support moment is quite consistent at all speeds.

4. Moments at the knee and hip are highly variable at all cadences but decrease their variability as cadence increases;

5. Mechanical power patterns at all joints show consistent timing over the stride period;

6. EMG profiles of 5 muscles show consistent timing over the stride, but the amplitude increases as walking speed increases.

Arguments are presented to support the concept that walking speed is largely controlled by gain and that the timing of the motor patterns, which is extremely tightly synchronized with the anatomical position, is under major afferent control.     

Everyday tasks impair spatiotemporal variables of gait in older adults with Parkinson's disease

IntroductionAlthough it is known that individuals with Parkinson's disease (PD) have difficulties performing dual-task activities, most of the studies have verified the effect of dual tasks on gait using tasks that are uncommon to perform while walking. However, the realization of tasks involving gait that really represents the daily activities carried out by the participants, allow us to detect real fall risk situations of individuals with PD during their gait.ObjectiveOur aim was to verify the influence of daily-life dual-tasks on gait spatiotemporal variables of the older adults with PD.Methods20 older adults without PD and 20 older adults with PD participated in the study. Gait kinematic was analyzed under three different conditions: walking without dual task, walking carrying bags with weight, and walking talking on the cell phone.ResultsOlder adults with PD presented lower speed (p = .001), cadence (p = .039), and shorter step length (p = .028) than older adults without PD during walking without dual tasks. When walking while carrying bags with weight, older adults with PD had a lower speed (p < .001), cadence (p = .015), shorter step length (p = .008), and greater double support time (p = .021) compared with older adults without PD. During walking while talking on the cell phone, older adults with PD walked with lower speed (p < .001), cadence (p = .013), shorter step length (p = .001) and swing time (p = .013), and increased double support time (p = .008) and support time (p = .014) in relation to older adults without PD.ConclusionDaily-life dual tasks impair the spatiotemporal variables of gait in the older adults with PD, which was most evident during walking talking on the cell phone.     

The effect of dividing attention between walking and auxiliary tasks in people with Parkinson's disease

This controlled study examined the effects of dividing attention between walking and the performance of a secondary cognitive task in people with mild to moderate Parkinson's disease (Hoehn and Yahr stages 2-3.5). Participants in the training group (n=6) received 30 min divided attention training in taking big steps while simultaneously performing serial three subtractions. Participants in the control group (n=6) received no training. Stride length, gait velocity and accurate enumeration rate were measured at baseline, immediate after training and 30 min after training under single-task (walk only or subtract only) and dual-task (walk and subtract) conditions. Data were also collected at training in the training group. Immediate improvement in stride length and gait velocity was found when instruction was given to participants to pay equal attention to gait and subtractions (p=0.001, p=0.05) compared to baseline. Short-term improvement in the gait variables was also found after training when compared to the controls (p=0.001, p=0.001). Nevertheless, there was no significant difference in the accurate enumeration rate. Based on the findings, we conclude that divided attention can be used as a strategy to improve slow and short-stepped gait under dual-task conditions. Divided attention can also be used in gait training for short term stride length and gait velocity improvement.     

Relationships between dual-task related changes in stride velocity and stride time variability in healthy older adults

Dual-task related gait changes have been previously reported for healthy older adults, suggesting that gait control requires attention. Compared to balance control, the involvement of attention in the control of the rhythmic stepping mechanism, as reflected by stride time variability, is not well known. In particular, under dual-task, the relative contributions of a second, attention-demanding task and changes in walking speed remain unclear. Thus, the aims of this study were (1) to assess whether walking with a slow-selected speed or walking while performing an attention-demanding task affected stride time variability in a sample of healthy older participants, and (2) to establish whether stride time variability under dual-task conditions is related either to the decrease of walking speed or the simultaneous attention-demanding task, or to both. Forty-five healthy older participants performed four experimental conditions: (1) walking at a normal self-selected speed, (2) walking at a slow self-selected speed, (3) performing a verbal fluency task when sitting on a chair, and (4) performing the verbal fluency task while walking at self-selected walking speed. Gait parameters were recorded across 15 meters, using Physilog. Results showed a significant dual-task related decrease in mean values of stride velocity, as well as a significant increase in mean values and coefficients of variation of stride time. These dual-task related changes in stride time were explained by the simultaneous performance of the verbal fluency task, the decrease of gait speed and the variability between participants. Although a relationship exists between decreased walking speed and increased stride time variability, the dual-task related increase of stride time variability was also significantly associated with the attention-demanding task, suggesting some attentional control for the rhythmic stepping mechanism of walking in healthy older adults.     

Effect of different residential settings on gait kinematic parameters in older adults with cognitive impairment

ObjectiveTo compare the parameters of gait kinematics of older adults with cognitive impairment who live in community dwellings or those living or spending most of the time in non-family environment settings.MethodsThe sample was composed of 33 older adults of both sexes with cognitive impairment. Participants were separated into three groups: a community-dwelling older adult group comprised of 11 subjects; a semi-institutionalized older adult group comprised of 10 older adults attended in a geriatric daycare institution; and an institutionalized older adult group comprised of 12 older adults living in long-term institutions. Gait kinematics were recorded by pressure sensors (footswitches). Fifty gait cycles at self-selected pace were analyzed to obtain: gait speed, stride length, stance, swing, and stride time. The variability of these parameters was also analyzed.ResultsMANCOVA identified the main effect of groups (p < 0.001). Gait speed of older adults living in long-term institutions and older adults attended in geriatric daycare institutions was slower than community-living older adults (p < 0.001 and p = 0.04, respectively). Swing and stride time variability was higher in older adults living in long-term institutions (p = 0.003 and p = 0.001) and in older adults attended in geriatric daycare institutions (p = 0.02 and p = 0.001) than in community-dwelling older adults.ConclusionThe most important finding was that older adults with cognitive impairment who need non-family residential setting care had higher gait kinematics abnormalities, which may increase the risk of falls, compared to those who live in the community.     

Investigating the efficacy of a tactile feedback system to increase the gait speed of older adults

The objective of this study was to determine (1) if a novel haptic feedback system could increase the walking speed of older adults while it is being employed during overground walking and (2) whether the frequency at which this feedback was presented would have a differential impact on the ability of users to change walking speed while it was present. Given that peak thigh extension has been found to be a biomechanical surrogate for stride length, and consequently gait speed, vibrotactile haptic feedback was provided to the participants' thighs as a cue to increase peak thigh extension while the effect on gait speed was monitored. Ten healthy community-dwelling older adults (68.4 ± 4.1 years) participated. Participants' peak thigh extension, cadence, normalized stride length and velocity, along with their coefficients of variation (COV) were compared across baseline normal and fast walking (with no feedback) and three different frequency of feedback conditions. The findings indicated that, compared to self-selected normal and fast walking speeds, peak thigh extension was significantly increased when feedback was present and after it was withdrawn in a post-test. An increase in thigh extension led to an increase in stride length and, consequently, an increase in stride velocity compared to normal speed. There were no significant differences in the gait parameters as a function of feedback frequency during its application. In conclusion, while present, the haptic feedback system increased thigh extension and walking speed in older adults regardless of the feedback frequency and when the feedback was withdrawn, participants could maintain an increase in those parameters.     

Residual attentional capacity amongst young and elderly during dual and triple task walking

Walking is considered an automatic function which demands little attentional resources. Thus a residual attentional capacity is available for a concurrent task (dual task). Minor age-related deficits in postural control may minimize the residual attentional capacity, however this may not be detected by a simple examination of the individuals gait performance. This study investigated the use of challenging dual task combinations to detect age related changes in gait performance. Eleven community-dwelling elderly (mean age 76 years) and 13 young subjects (mean age 26 years) participated in the study. The participants walked along a figure-of-eight track at a self-selected speed. The effect of introducing a concurrent cognitive task and a concurrent functional motor task was evaluated. Stride-to-stride variability was measured by heel contacts and by trunk accelerometry. In response to the cognitive task the elderly increased their temporal stride-to-stride variability by 39% in the walking task and by 57% in the combined motor task. These increases were significantly larger than observed for the young. Equivalent decreases in trunk acceleration autocorrelation coefficients and gait speed were found. A combination of sufficiently challenging motor tasks and concurrent cognitive tasks can reveal signs of limited residual attentional capacity during walking amongst the elderly.     

Emotional states influence forward gait during music listening based on familiarity with music selections

Music elicits a wide range of human emotions, which influence human movement. We sought to determine how emotional states impact forward gait during music listening, and whether the emotional effects of music on gait differ as a function of familiarity with music. Twenty-four healthy young adults completed walking trials while listening to four types of music selections: experimenter-selected music (unfamiliar-pleasant), its dissonant counterpart (unfamiliar-unpleasant), each participant’s self-selected favorite music (familiar-pleasant), and its dissonant counterpart (familiar-unpleasant). Faster gait velocity, cadence, and stride time, as well as longer stride length were identified during pleasant versus unpleasant music conditions. Increased gait velocity, stride length, and cadence as well as reduced stride time were positively correlated with subjective ratings of emotional arousal and pleasure as well as musical emotions such as happiness-elation, nostalgia-longing, interest-expectancy, pride-confidence, and chills, and they were negatively related to anger-irritation and disgust-contempt. Moreover, familiarity with music interacted with emotional responses to influence gait kinematics. Gait velocity was faster in the familiar-pleasant music condition relative to the familiar-unpleasant condition, primarily due to longer stride length. In contrast, no differences in any gait parameters were found between unfamiliar-pleasant and unfamiliar-unpleasant music conditions. These results suggest emotional states influence gait behavior during music listening and that such effects are altered by familiarity with music. Our findings provide fundamental evidence of the impact of musical emotion on human gait, with implications for using music to enhance motor performance in clinical and performance settings.     

Central executive function in mild cognitive impairment: a PET activation study

Using positron emission tomography (PET), we explored the neural correlates of an executive function, dual tasking, in patients with amnestic mild cognitive impairment (aMCI) and in elderly controls. The experiment employed simple auditory and visual tasks that were presented both in isolation and simultaneously to create a task condition requiring enhanced attentional control. Behaviorally, both groups performed well, albeit the patients made more errors on the visual task. The PET analysis focused at prefrontal regions where group differences in task-related activation patterns were expected. During dual task performance, the patients showed attenuated activity in the left inferior frontal region when compared to the controls. This suggests abnormalities in the neural processes underlying attentional control in aMCI.     

Functional Mobility in a Divided Attention Task in Older Adults With Cognitive Impairment

ABSTRACT. 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.