Évaluation posturale à domicile chez la personne âgée : comparaison chuteurs–non chuteurs

A review of center of pressure (COP) variables to quantify standing balance in elderly people: Algorithms and open-access code

Postural control is often quantified by recording the trajectory of the center of pressure (COP)-also called stabilogram-during human quiet standing. This quantification has many important applications, such as the early detection of balance degradation to prevent falls, a crucial task whose relevance increases with the aging of the population. Due to the complexity of the quantification process, the analyses of sway patterns have been performed empirically using a number of variables, such as ellipse confidence area or mean velocity. This study reviews and compares a wide range of state-of-the-art variables that are used to assess the risk of fall in elderly from a stabilogram. When appropriate, we discuss the hypothesis and mathematical assumptions that underlie these variables, and we propose a reproducible method to compute each of them. Additionally, we provide a statistical description of their behavior on two datasets recorded in two elderly populations and with different protocols, to hint at typical values of these variables. First, the balance of 133 elderly individuals, including 32 fallers, was measured on a relatively inexpensive, portable force platform (Wii Balance Board, Nintendo) with a 25-s open-eyes protocol. Second, the recordings of 76 elderly individuals, from an open access database commonly used to test static balance analyses, were used to compute the values of the variables on 60-s eyes-open recordings with a research laboratory standard force platform.

Center of pressure displacement characteristics differentiate fall risk in older people: A systematic review with meta-analysis

Falling is the second most prevalent cause of accidental death in the world. Currently available clinical tests to assess balance in older people are insufficiently sensitive to screen for fall risk in this population. Laboratory tests that record the center of pressure (COP) trajectory could overcome this problem but despite their widespread use, the choice of COP trajectory features for use as a biomarker of fall risk lacks consensus. This systematic review and meta-analysis aimed at identifying the best COP characteristics to predict risk of falling in older adults. More than 4000 articles were screened; 44 (7176 older adults) were included in this study. Several COP parameters emerged as good indices to discriminate fallers from non-fallers. From sensitivity analysis, Sway area per unit time, anteroposterior mean velocity, and radial mean velocity were the best traditional features. In this study, identification of older people with a high fall risk was demonstrated using quiet-standing recordings. Such screening would also be useful for routine follow-up of balance changes in older fallers in clinical practice.

Active ocular vergence improves postural control in elderly as close viewing distance with or without a single cognitive task

Performance of the vestibular, visual, and somatosensory systems decreases with age, reducing the capacity of postural control, and increasing the risk of falling. The purpose of this study is to measure the effects of vision, active vergence eye movements, viewing distance/vergence angle and a simple cognitive task on postural control during an upright stance, in completely autonomous elderly individuals. Participated in the study, 23 elderly subjects (73.4 ± 6.8 years) who were enrolled in a center dedicated to the prevention of falling. Their body oscillations were measured with the DynaPort(®) device, with three accelerometers, placed at the lumbosacral level, near the center of mass. The conditions were the following: eyes open fixating on LED at 20 cm or 150 cm (vergence angle 17.0° and 2.3° respectively) with or without additional cognitive tasks (counting down from one hundred), performing active vergence by alternating the fixation between the far and the near LED (convergence and divergence), eyes closed after having fixated the far LED. The results showed that the postural stability significantly decreased when fixating on the LED at a far distance (weak convergence angle) with or without cognitive tasks; active convergence-divergence between the LEDs improved the postural stability while eye closure decreased it. The privilege of proximity (with increased convergence at near), previously established with foot posturography, is shown here to be valid for accelerometry with the center of mass in elderly. Another major result is the beneficial contribution of active vergence eye movements to better postural stability. The results bring new perspectives for the role of eye movement training to preserve postural control and autonomy in elderly.

Reliability analysis of time series force plate data of community dwelling older adults

Frequency-based analysis of body sway has been used to distinguish between healthy young, healthy elderly adults and elderly adults with Huntingtons disease. Our aim was to assess the reliability of spectral-based outcomes of the centre of pressure (CoP) kinematics in order to determine if these outcomes could be tested for their capability to distinguish between elderly fallers and non-fallers in a future study. We have studied balance for 30 community dwelling healthy older adults 60 years or older. Four test conditions were used. Three successive trials were performed for each condition. CoP kinematics were estimated with a force platform with three strain gauges set in a triangular position. The frequency content of these signals was estimated. Intrasession correlation coefficients (ICC's) were then calculated for all test conditions. The reliability of the selected parameters varied between low and high (ICC 0.652-0.939). The ICC's for the narrow stance tests were higher compared to tests with normal standing conditions (0.771-0.94) to (0.652-0.865). The highest value was obtained in the high frequency band (0.939). These measures should be viewed with caution when screening geriatric patients because their reliability cannot always be assumed.

Episodes of falling among elderly people: a systematic review and meta-analysis of social and demographic pre-disposing characteristics

CONTEXT

The multifactorial nature of falls among elderly people is well-known. Identifying the social-demographic characteristics of elderly people who fall would enable us to define the typical profile of the elderly who are at risk of falling.

OBJECTIVE

We aimed to isolate studies in which the social-demographic risk factors for falls among the elderly have been evaluated and to carry out a meta-analysis by combining the results of all of these selected studies.

METHOD

We did a systematic literature review using the key words "accidental fall / numerical data" and "risk factors." Inclusion criteria entailed the selection of articles with the following characteristics: population of subjects aged 60 years or over, falls that took place in everyday life, and social-demographic risk factors for falls.

RESULTS

3,747 indexed articles published between 1981 and 2007 were identified, and 177 studies with available data were included, of which 129 had data on social-demographic risk factors for falls. Difficulties in activities of daily living (ADL) or in instrumental activities of daily living (IADL) double the risk of falling: The OR and 95% Cl were 2.26 (2.09, 2.45) for disturbance ADL and 2.10 (1.68, 2.64) for IADL. The OR and 95% Cl for Caucasians were 1.68 (0.98 - 2.88) and 0.64 (0.51 - 0.80) for Hispanics. In the subgroup of patients older than eighty, being married protected people from falling with an OR and 95% Cl =0.68 (0.53 - 0.87).

CONCLUSION

Defining factors that create a risk of falling and protect elderly people from falls using social-demographic characteristics lets us focus on an "at risk" population for which a specific program could be developed.

Task-specific measures of balance efficacy, anxiety, and stability and their relationship to clinical balance performance

The main objective of this research was to investigate the effects of postural threat on performance of three clinical balance tests. Thirty-one healthy young adults performed quiet stance, maximal reach, and one-leg stance tasks at two levels of postural threat, which was modified through the use of a hydraulic lift. Increased postural threat significantly affected postural control measures for both simple and dynamic balance tests. Physiological and state anxiety increased as a result of increased postural threat whereas ratings of perceived stability and balance efficacy were reduced as a function of increased postural threat. Efforts to diagnose balance disorders based on balance performance may be confounded by the influence of psychological factors.

Posturographic Changes Associated with Music Listening

OBJECTIVES

The aim of this study was to ascertain whether listening to music might cause changes in human stability and be useful in fall prevention and rehabilitation. The aim was also to find what percentage of subjects without neurologic signs or symptoms associated with falling had less than ideal stability.

DESIGN

Computer dynamic posturography (CDP) provided stability scores in 266 subjects without a history of falls or vertigo. Subjects were randomized into several different music listening groups and one control group. The music listening groups were given a daily specific music listening task and CDP was obtained 10 minutes, 1 week, and 1 month after the subject's treatment in a blinded fashion.

RESULTS

Tests of postural stability have shown that 73% of 266 subjects without neurologic signs or symptoms were found to have balance abnormalities associated with an increased probability of falling. We have demonstrated positive changes in stability scores in these subjects who underwent a variety of music listening tasks, with the music of Nolwenn Leroy found to be significantly superior to other music tested.

CONCLUSIONS

Listening to certain types of music has the potential to change human stability and promote change in the field of fall prevention and rehabilitation with a potential to decrease disability.

Distance impairs postural stability only under binocular viewing

Prior studies indicate that postural stability under binocular viewing is not better than under monocular viewing. This was tested at the distances of 145 cm [Fox, C.R. (1990). Some visual influences on human postural equilibrium: binocular versus monocular fixation. Perception and Psychophysics, 47 (5), 409-422] and 90 cm [Isotalo, E., Kapoula, Z., Feret, P.H., Gauchon, K., Zamfirescu, F., & Gagey, P.M. (2004). Monocular versus binocular vision in postural control. Auris Nasus Larynx, 31 (1), 11-17]. On the other hand, postural stability is known to decrease with distance increase. We re-examined the effect of binocular versus monocular viewing on postural stability at near and far distances (40 and 200 cm), and for both young (25.7+/-2.7 years), and old subjects (61.2+/-4.6 years). For both groups of subjects, proximity decreased the area of CoP, the standard deviation of antero-posterior sway (SDy) and the variance of speed. The group of elderly presented increased variance of speed at far distance in comparison with young subjects. The novel finding is the interaction between distance and viewing condition. Under binocular viewing, the area of CoP was significantly higher at far distance than at near; in contrast, monocular viewing produced similar CoP values at both distances. Increased instability at far distance when both eyes are viewing is attributed to decreased sensitivity to binocular disparity cues and to visual motion in depth resulting from body sway. Monocular viewing would provide similar stability at far and at near distance, because sensitivity to lateral visual motion, detected monocularly, decreases less with distance than sensitivity to binocularly detected motion in depth. Alternatively, such monocular viewing could increase subject's attention and lead to tighter postural control regardless of the distance.

Rôle du Neurocom Balance Master® dans l'évaluation des troubles de l'équilibre et du risque de chute chez le sujet âgé

INTRODUCTION

Falls in elderly people is currently a health service problem because of the multiple consequences. Numerous teams have been interested in predicting the risk of falling with clinical and instrumental tests. Our study investigated instrumental evaluation by use of the Neurocom Balance Master in the global assessment of gait problems and risk of falling in elderly people.

PATIENTS AND METHODS

Transverse study concerning 60 subjects older than 65 years distributed in 2 groups of 30 subjects each according to the existence or not of falling incidents during the past year. Evaluation by the Balance Master involved the following items: 1) the modified Clinical Test for the Sensory Interaction on Balance (CTSIB), which estimates balance by measuring the speed of oscillation of the center of pressure (CP) with open then closed eyes and firm then mossy ground; 2) support monopodal 5" to the left then to the right, eyes open then closed in moderated speeds of oscillation of the CP; 3) passage from standing to sitting, in moderated speeds of oscillation of the CP; 4) limits of stability: the possibilities of moving the CP towards a predetermined target without moving the feet in moderated time and speed; 5) study of the step: determine length and width of the step as well as speed; 6) most about-turn: measure of speed of oscillation of the CP during the right then left about-turn; 7) clearing: the force of the impact and the oscillations of the CP during the clearing of an obstacle 10 cm high to measure leverage.

RESULTS

The oscillation speed of the CP in the 2 groups during modified CTSIB, support monopodal 5", passage from standing to sitting, about-turn and clearing were significantly improved the group of the patients with falls (P < 0.05). The step, length and speed of these patients were significantly reduced, with no difference in width of the step between the 2 groups. In the evaluation of the limits of stability, only time necessary to reach the target was significantly increased in the group with falls. Finally, the indication of leverage and the force of impact on the ground measured by the test of clearing were more important in the group of fallers than in non-fallers.

CONCLUSION

The Neurocom Balance Master estimates not only postural balance, but also the vestibulary system and reproduces the physiological conditions of daily life. It has a certain role in the early assessment of gait problems and the risk of falling. This system also allows for rehabilitation of the impaired balance and offers a profit with the biofeedback.

Effects of distance and gaze position on postural stability in young and old subjects

Visual stabilization of posture is known to improve when the distance to target fixation decreases; this is attributed to increased angular size of retinal slip induced by body sway. At near distance, however, the eyes converge and efferent or afferent oculomotor signals could also be involved in posture stabilization. The goal of this study is to test whether the distance effect exists for both young and elderly and to test the role of vergence itself and of gaze position. Eighteen young (25.3 years) and 17 elderly (61.6 years) subjects were asked to fixate a target in quiet stance presented either at close (40 cm) or at far distance (200 cm); the vergence angle was 9 degrees and 2 degrees , respectively. For each distance, three gaze positions were studied straight-ahead (0 degrees ), 15 degrees up or down. We found a decrease in the surface of center of pressure (CoP), of standard deviation of antero-posterior and lateral body sway and of speed variance at near distance that occurs for both young and elderly. At far distance, the surface of CoP is smaller for 15 degrees up or down gaze in comparison with straight-ahead position, but at near distance there is no such gaze position effect. In an additional experiment, subjects fixated a target at far distance (200 cm) but prisms were used to cause the eyes to converge by an amount similar to that required for 40 cm viewing distance. The use of prisms decreased surface of CoP to values similar to those for natural near viewing distance. The effect of gaze position and of convergence (experiment with prisms) leads us to suggest that in addition to retinal slip, the ocular motor signals and perhaps related neck muscle activity are involved in postural stabilization. Finally, the elderly presented higher speed variance of CoP than the young subjects even though the surface itself was similar to adult values. We suggest that increment of speed variance is the first sign of senescence in postural control.