Claudine J. C. Lamoth

Gait stability and variability measures show effects of impaired cognition and dual tasking in frail people

BackgroundFalls in frail elderly are a common problem with a rising incidence. Gait and postural instability are major risk factors for falling, particularly in geriatric patients. As walking requires attention, cognitive impairments are likely to contribute to an increased fall risk. An objective quantification of gait and balance ability is required to identify persons with a high tendency to fall. Recent studies have shown that stride variability is increased in elderly and under dual task condition and might be more sensitive to detect fall risk than walking speed. In the present study we complemented stride related measures with measures that quantify trunk movement patterns as indicators of dynamic balance ability during walking. The aim of the study was to quantify the effect of impaired cognition and dual tasking on gait variability and stability in geriatric patients.MethodsThirteen elderly with dementia (mean age: 82.6 ± 4.3 years) and thirteen without dementia (79.4 ± 5.55) recruited from a geriatric day clinic, walked at self-selected speed with and without performing a verbal dual task. The Mini Mental State Examination and the Seven Minute Screen were administered. Trunk accelerations were measured with an accelerometer. In addition to walking speed, mean, and variability of stride times, gait stability was quantified using stochastic dynamical measures, namely regularity (sample entropy, long range correlations) and local stability exponents of trunk accelerations.ResultsDual tasking significantly (p < 0.05) decreased walking speed, while stride time variability increased, and stability and regularity of lateral trunk accelerations decreased. Cognitively impaired elderly showed significantly (p < 0.05) more changes in gait variability than cognitive intact elderly. Differences in dynamic parameters between groups were more discerned under dual task conditions.ConclusionsThe observed trunk adaptations were a consistent instability factor. These results support the concept that changes in cognitive functions contribute to changes in the variability and stability of the gait pattern. Walking under dual task conditions and quantifying gait using dynamical parameters can improve detecting walking disorders and might help to identify those elderly who are able to adapt walking ability and those who are not and thus are at greater risk for falling.

Gait and cognition: The relationship between gait stability and variability with executive function in persons with and without dementia

Besides cognitive decline, dementia is characterized by gait changes and increased fall risk, also in early stages of the disease. The aim of this study was to investigate differences in the relationship between executive function and gait variability and stability during single task and dual task walking in persons with and without dementia. The study sample consisted of three groups: fifteen dementia patients (aged 75-87), fourteen healthy elderly (aged 75-85), and twelve relatively younger elderly (aged 55-70). Participants underwent neuropsychological testing and tests of single and dual task walking while wearing an accelerometer. Outcome measures include stride related measures such as mean and coefficient of variation of stride time, and dynamic measures regarding the magnitude, smoothness, predictability and local stability of trunk accelerations. Patients with dementia exhibited a significantly (p<.05) less variable, but more irregular trunk acceleration pattern than cognitively intact elderly on single and dual task walking. The walking pattern during dual tasking for the whole group became increasingly unstable, even though participants modified their gait pattern by slowing their walking speed, and decreasing the magnitude of trunk accelerations. Moderate to high correlations (r>.51) were found between executive tasks and gait parameters. In conclusion, these findings indicate that decreased executive function plays an important role in increased gait variability in dementia patients; a fact that should be considered when designing fall risk interventions for this population. Furthermore, results indicate that measures of gait variability and stability should be deemed worthwhile in the diagnosis of dementia.

Exergaming for balance training of elderly: state of the art and future developments

Fall injuries are responsible for physical dysfunction, significant disability, and loss of independence among elderly. Poor postural control is one of the major risk factors for falling but can be trained in fall prevention programs. These however suffer from low therapy adherence, particularly if prevention is the goal. To provide a fun and motivating training environment for elderly, exercise games, or exergames, have been studied as balance training tools in the past years. The present paper reviews the effects of exergame training programs on postural control of elderly reported so far. Additionally we aim to provide an in-depth discussion of technologies and outcome measures utilized in exergame studies. Thirteen papers were included in the analysis. Most of the reviewed studies reported positive results with respect to improvements in balance ability after a training period, yet few reached significant levels. Outcome measures for quantification of postural control are under continuous dispute and no gold standard is present. Clinical measures used in the studies reviewed are well validated yet only give a global indication of balance ability. Instrumented measures were unable to detect small changes in balance ability as they are mainly based on calculating summary statistics, thereby ignoring the time-varying structure of the signals. Both methods only allow for measuring balance after the exergame intervention program. Current developments in sensor technology allow for accurate registration of movements and rapid analysis of signals. We propose to quantify the time-varying structure of postural control during gameplay using low-cost sensor systems. Continuous monitoring of balance ability leaves the user unaware of the measurements and allows for generating user-specific exergame training programs and feedback, both during one game and in timeframes of weeks or months. This approach is unique and unlocks the as of yet untapped potential of exergames as balance training tools for community dwelling elderly.

Variability and stability analysis of walking of transfemoral amputees

Variability and stability of walking of eight transfemoral amputees and eight healthy controls was studied under four conditions: walking inside on a smooth terrain, walking while performing a dual-task and walking outside on (ir)regular surfaces. Trunk accelerations were recorded with a tri-axial accelerometer. Walking speed, mean and coefficient of variation of stride times (ST) and the root mean squares (RMS) of trunk accelerations was calculated. Gait variability and stability were quantified using measures derived from the theory of stochastic dynamics. Regularity was indexed using the sample entropy (SEn) and the scaling exponent α derived form Detrended Fluctuations Analysis. Local stability (LSE) quantified gait stability. Walking speed was lower, but ST variability was not different for amputees than controls. RMS of medio-lateral accelerations was higher for amputees; SEn was higher, implying less predictable accelerations, and LSE higher, indicating decreased stability. The largest condition effect was present for walking outside: trunk RMS increased and LSE decreased. Differences in walking between amputees and healthy controls and their responses to perturbations revealed themselves in the magnitude, variability and stability measures of trunk accelerations. These results imply that quantifying the dynamical structure of trunk accelerations can differentiate between groups with different walking abilities and between conditions of increasing difficulty and may therefore provide a useful diagnostic tool.

Suitability of Kinect for measuring whole body movement patterns during exergaming

Exergames provide a challenging opportunity for home-based training and evaluation of postural control in the elderly population, but affordable sensor technology and algorithms for assessment of whole body movement patterns in the home environment are yet to be developed. The aim of the present study was to evaluate the use of Kinect, a commonly available video game sensor, for capturing and analyzing whole body movement patterns. Healthy adults (n=20) played a weight shifting exergame under five different conditions with varying amplitudes and speed of sway movement, while 3D positions of ten body segments were recorded in the frontal plane using Kinect and a Vicon 3D camera system. Principal Component Analysis (PCA) was used to extract and compare movement patterns and the variance in individual body segment positions explained by these patterns. Using the identified patterns, balance outcome measures based on spatiotemporal sway characteristics were computed. The results showed that both Vicon and Kinect capture >90% variance of all body segment movements within three PCs. Kinect-derived movement patterns were found to explain variance in trunk movements accurately, yet explained variance in hand and foot segments was underestimated and overestimated respectively by as much as 30%. Differences between both systems with respect to balance outcome measures range 0.3-64.3%. The results imply that Kinect provides the unique possibility of quantifying balance ability while performing complex tasks in an exergame environment.

Sports activities are reflected in the local stability and regularity of body sway: Older ice-skaters have better postural control than inactive elderly

With age postural control deteriorates and increases the risk for falls. Recent research has suggested that in contrast to persons with superior balance control (dancers athletes), with pathology and aging, predictability and regularity of sway patterns increase and stability decreases implying a less adaptive form of postural control. The aim of the present study was to determine, whether patterns of body sway of elderly (N=13) who practice a sport which challenges postural control (ice speed-skating), are more similar to that of young subjects (N=10) than to that of inactive elderly (N=10). Trunk patterns were measured with a tri-axial accelerometer. Data were recorded during quiet upright stance with (1) eyes open, (2) limited vision, and (3) while performing a dual task. Anterior-posterior and medio-lateral acceleration time-series were analyzed. Differences in postural control were quantified in terms of the magnitude of the acceleration (root mean square), the smoothness (mean power frequency), the predictability (sample entropy) and the local stability (largest Lyapunov exponent). Postural control of ice-skating elderly differed from that of sedentary elderly. As anticipated, postural control of the ice-skating elderly was similar to that of young adults. For anterior-posterior accelerations, the skating elderly and the younger subjects had significant higher stability and lower regularity than the non-skating elderly in all tasks. These results imply that sport activities such as ice-skating are beneficial for elderly people. It might, at least partly, counteract the age related changes in postural control.

Sensor technologies aiming at fall prevention in institutionalized old adults: A synthesis of current knowledge

BACKGROUND Falls are a serious health problem in old adults especially in nursing home residents and hospitalized patients. To prevent elderly from falling, sensors have been increasingly used in intramural care settings. However, there is no clear overview of the current used technologies and their results in fall prevention. OBJECTIVES The present study reviews sensor systems that prevent falls in geriatric patients living in an intramural setting and describe fall rates, fall-related injuries, false alarms, and user experience associated with such systems. METHODS We conducted a systematic search for studies that used sensor technologies with the aim to prevent falls in institutionalized geriatric patients. RESULTS A total of 12 studies met the search criteria. Three randomized clinical trials reported no reductions in fall rate but three before-after studies reported significant reductions of 2.4-37 falls per 1000 patient days. Although there was up to 77% reduction in fall-related injuries and there was relatively low, 16%, rate of false alarms, the current data are inconsistent whether current sensor technologies are effective in reducing the number of falls in institutionalized geriatric patients. The occurrence of false alarms (16%) was too high to maintain full attention of the nursing staff. Additionally including the users opinion and demands in developing and introducing sensor systems into intramural care settings seems to be required to make an intervention successful. CONCLUSION The evidence is inconsistent whether the current sensor systems can prevent falls and fall-related injuries in institutionalized elderly. Further research should focus more comprehensively on user requirements and effective ways using intelligent alarms.

The Effects of Fall-Risk-Increasing Drugs on Postural Control: A Literature Review

Meta-analyses showed that psychotropic drugs (antidepressants, neuroleptics, benzodiazepines, antiepileptic drugs) and some cardiac drugs (digoxin, type IA anti-arrhythmics, diuretics) are associated with increased fall risk. Because balance and gait disorders are the most consistent predictors of future falls, falls due to use of these so-called fall-risk-increasing drugs (FRIDs) might be partly caused by impairments of postural control that these drugs can induce. Therefore, the effects of FRIDs on postural control were examined by reviewing literature. Electronic databases and reference lists of identified papers were searched until June 2013. Only controlled research papers examining the effects of FRIDs on postural control were included. FRIDs were defined according to meta-analyses as antidepressants, neuroleptics, benzodiazepines, antiepileptic drugs, digoxin, type IA anti-arrhythmics, and diuretics. Ninety-four papers were included, of which study methods for quantifying postural control, and the effects of FRIDs on postural control were abstracted. Postural control was assessed with a variety of instruments, mainly evaluating aspects of body sway during quiet standing. In general, postural control was impaired, indicated by an increase in parameters quantifying body sway, when using psychotropic FRIDs. The effects were more pronounced when people were of a higher age, used psychotropics at higher daily doses, with longer half-lives, and administered for a longer period. From the present literature review, it can be concluded that psychotropic drugs cause impairments in postural control, which is probably one of the mediating factors for the increased fall risk these FRIDs are associated with. The sedative effects of these drugs on postural control are reversible, as was proven in intervention studies where FRIDs were withdrawn. The findings of the present literature review highlight the importance of using psychotropic drugs in the older population only at the lowest effective dose and for a limited period of time.

Exergaming for elderly:: effects of different types of game feedback on performance of a balance task.

Balance training to improve postural control in elderly can contribute to the prevention of falls. Video games that require body movements have the potential to improve balance. However, research about the effects of type of visual feedback (i.e. the exergame) on the quality of movement and experienced workout intensity is scarce. In this study twelve healthy older and younger subjects performed anterior-posterior or mediolateral oscillations on a wobble board, in three conditions: no feedback, real-time visual feedback, and real-time visual feedback with a competitive game element. The Elderly moved slower, less accurately and more irregularly than younger people. Both feedback conditions ensured a more controlled movement technique on the wobble-board and increased experienced workout intensity. The participants enjoyed the attention demanding competitive game element, but this game did not improve balance performance more than interacting with a game that incorporated visual feedback. These results show the potential of exergames with visual feedback to enhance postural control.

Energy expenditure of stroke patients during postural control tasks

Two common impairments in patients after stroke are loss of balance control and fatigue. We propose that both could be inter-related. The purpose of this study was to investigate the metabolic energy demand for balance control in patients after stroke during upright standing. Ten stroke patients and 12 able-bodied controls performed four 5-min upright standing tasks on a force plate; unperturbed (SU), blindfolded (SUB), on foam surface (SUF) and with feet parallel against each other (SUP). Metabolic energy expenditure, posturography measures and muscle activity (EMG) of lower leg muscles were measured. Patients required on average 125% (33Jkg(-1)s(-1)) more metabolic energy for upright standing under the various conditions than controls. In addition, balance manipulation significantly (p<0.05) affected energy expenditure (21% higher in SUB, 52% in SUF, 40% in SUP compared to SU). Although the increase in energy expenditure was on average twice as high in patients than controls no significant group by condition interaction effect was found. Overall correlations between posturography measures, EMG and energy expenditure (r=0.33-0.60) were significant (p<0.001). We conclude that impaired balance control puts an extra demand on the energy expenditure during motor activities in stroke patients. This should be considered when prescribing interventions aimed at reducing physiological strain.