Permanent URL to this publication: http://dx.doi.org/10.5167/uzh-29147
Swanenburg, J. Maintaining Balance in Elderly Fallers: Novel aspects of postural balance measures in elderly. 2009, University Hospital of Zurich, Faculty of Medicine.
At first in this thesis, an intervention programme was tested for the effect on the risk of falling in a population of elderly. The aim of the study was to investigate if exercise, combined with protein intake and calcium/vitamin D supplementation would have a larger effect on the risk of falling and postural balance outcomes than calcium/vitamin D supplementation only. An observational performance test (risk of falling) and performance measurements (force platform) were used as outcome measures.
The results of this study were a reduced risk of falling and less falls within the intervention group but no change of variables of the force platform. Based on this contrary result, the following questions were raised:
a)Was the test postural balance measurement protocol not challenging enough to detect any balance deficits?
b)Are force platform test sensitive enough to detect any change - in a normal and in a challenging situation?
c)Are these force platform test protocols able to predict any fall - in a normal and in a challenging situation?
d)What is the relation of postural stability and challenging measurement environment?
The postural balance measurement environment in Chapter 2 could have been too simple for most elderly to detect any differences between fallers and non-fallers. Would an additional task change the measurement environment in such a way to detect any differences? Which dual task would be the most appropriate? The additional task should have the most disturbing influence on fall-related force platform variables. Therefore, it should be possible to carry out the additional test (dual task) in a non-vision situation. Attention-demanding secondary tasks have shown deleterious effects on postural control in older adults1. One of these additional tasks is the counting backwards task. This task would meet with the requirements of disturbing balance and being executed in a non-vision situation 2-4. Until now, the influence of this task on postural stability has only been tested on healthy young volunteers5. They concluded that disturbances of counting backwards in postural control were caused by the vocal articulation of counting and not by the competing demands for attention5. In Chapter 3, an analysis of the results of Yardley and colleagues (1999) has been undertaken. Are the disturbances in postural control under dual-task conditions in elderly caused mainly by the additional motor effect of articulation (speaking aloud), or by the effect of an additional cognitive component of a task, or by a combination of the two? Furthermore, it was investigated whether differences exist between fallers and non-fallers in terms of disturbance of postural control under the different additional tasks. The findings suggest that the combined articulation and attention-demanding secondary task stressed the attentional system of elderly to such an extent that it compromised the performance of the primary task (quite standing). The counting backwards aloud task may be used as a dual task for clinical balance assessment in populations at risk of falling. This task was best able to disturb postural control.
The second question dealt with in Chapter 2 described question whether force platform tests are sensitive enough to detect any change. Although the reliability of fore plate’s measurement was determined in different studies, the dual tasking aspect was not taken into account. In addition, most of the reliability studies tested healthy people6-8. Until now, no reliability studies that included fallers have been reported. However, since one-third of community-dwelling people over 65 years of age experience one or more falls each year, it is important to include elderly fallers in reliability studies9-13. In Chapter 4 a study is described with how the interrater and test-retest reliability of force platform variables were tested. The variables tested were those which seemed to be the most appropriate to detect possible fallers and non-fallers. These variables were tested under single and dual-task conditions, with and without vision. This study showed good reliability results for group assessment and no systematic errors of the measurement protocol in measuring postural balance in the elderly in a single-task and dual-task condition.
The selection of posturography-derived parameters that discriminate between elderly fallers and nonfallers is shown to be inconclusive14. Next to the discrimination between elderly faller, an important goal of postural balance measures is the prediction of future falls with help of a forceplate. Piirtola and Era (2006) argued that the reason for not being able to predict future falls is related to the lack of studies in which a prospective design is used and that records falls as the primary outcome15. Therefore, more prospective fall assessment studies are needed that use posturography. A systematic evaluation of a balance with “complex conditions “protocol is needed to determine which posturography-derived balance variable is most associated with future falls. In their review, Zijlstra and colleagues (2008) showed that 2 studies provide some evidence that measurements with a dual task protocol could add some value for the prediction of falls. They recommended future studies with large sample size should investigate whether an overall performance score that combines the scores of the cognitive and balance task is more sensitive for predicting falls or detecting changes in balance performance than the individual balance or cognitive task score during dual-task performance16. In Chapter 5, a prospective study with 270 participants is described. The aim of this study was to determine whether postural balance variables measured with a forceplate with or without challenging conditions were able to prospectively predict fallers and non-fallers in a community-dwelling elderly population over a 12-month period. The challenging conditions applied were reduced vision and/or dual cognitive tasks. The findings show that the force platform variable RMS-ML (root-mean-square amplitude in medial-lateral directions) predicts future fall risk in women with a history of multiple falls who take fall-risk medications or use multiple medicines. Multiple fallers were also shown to position themselves with a narrower stance during balance testing.
The aim in Chapter 6 was to firstly determine postural balance changes caused by no-vision, compromised somatosensory information and a combination of no-vision and reduced somatosensory information in both single and dual tasking. Secondly, the aim was to determine the dual task costs (DTC) and the DTC change caused by the different test conditions. The combined reduction of sensory input (vision and compromised somatosensory) resulted in a decrease of dual-task costs for posture with at the same time no change in dual-task costs for cognition. This result refutes the often used theoretical framework of resource-sharing1 and the adaptive resource-sharing theory17. The findings, therefore, seem to provide support for the theory of an increased processing area18. The theory believes that the brain regions active for dual-task conditions highly overlap with regions found to be active for each of the single tasks and that the brain areas simply increase in magnitude with greater processing demands18 . The combined reduction of sensory input could have led the participants to greater processing area and therefore let them to generate more cognitive capacity. This increased cognitive capacity could hence be used to compensate for the sensory input reduction and for the cognitive task as well, which would explain the reduced dual-task costs for posture and absolute difference of sway in dual- and single-tasking situations.
In conclusion, this thesis showed new aspects of force platform measurements of elderly fallers and non-fallers. Future research could be conducted with force platform measurements to determine the effectiveness of intervention programmes, focused on fall prevention.
|Other titles:||Maintaining balance in elderly fallers : novel aspects of postural balance measures in elderly|
|Referees:||Arendzen J, Otten E, Scherder E J A, Diercks R, Hof A, Klipstein A, Zijlstra W|
|Communities & Collections:||04 Faculty of Medicine > University Hospital Zurich > Rheumatology Clinic and Institute of Physical Medicine|
|DDC:||610 Medicine & health|
|Deposited On:||23 Feb 2010 09:38|
|Last Modified:||09 Jul 2012 06:11|
|Number of Pages:||78|
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