Age-related changes in sensori-motor function, postural stability, functional balance and mobility.

Low Choy, Nancy (2008). Age-related changes in sensori-motor function, postural stability, functional balance and mobility. PhD Thesis, School of Health & Rehabilitation Sciences, The University of Queensland.

       
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n34817436_PhD_Abstract.pdf Final Thesis Lodgement 34817436_PhD_Abstract.pdf application/pdf 13.03KB 44
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Author Low Choy, Nancy
Thesis Title Age-related changes in sensori-motor function, postural stability, functional balance and mobility.
School, Centre or Institute School of Health & Rehabilitation Sciences
Institution The University of Queensland
Publication date 2008-05
Thesis type PhD Thesis
Supervisor Dr Sandra Brauer
Dr Jennifer Nitz
Total pages 483 (Including pages for acknowledgements & content
Total colour pages 13
Total black and white pages 470
Subjects 320000 Medical and Health Sciences
Formatted abstract The falls rate for ageing Australians has not decreased despite the implementation of a
range of interventions for older adults at risk of a fall. Reduced postural stability (balance)
is a known risk factor for falls and many studies have demonstrated detrimental changes in
sensori-motor factors in adults over 65 years. Few studies have studied the mid-life period
and concurrently investigated underlying sensori-motor contributors to changes in postural
stability across successive age decades. This research program addressed this gap by
investigating postural stability, demographics, health factors and sensori-motor function in
women aged 20 to 80 years. The overall objective of this research program was to improve
knowledge of the pre-clinical period of decline in postural stability and associated
demographic, health and sensori-motor factors to inform strategies towards healthier
ageing.
Two major cross-sectional studies of women were undertaken. In the first, laboratory and
clinical measures of postural stability were collected from 430 women aged 20 to 80 years
and compared across age decades. People with musculo-skeletal pathology and any
neurological disorder likely to contribute to postural instability were excluded from the
study with the age, height and weight of each participant measured and their reported health
and physical activity recorded. When velocity of sway was analysed across the 10-second
trial period, all test conditions demonstrated reduced postural stability from the 60s. The
tasks of bilateral stance (foam eyes open (EO) and eyes closed (EC)) and one-leg stance
(EO and EC) revealed the most interesting findings with increased velocity of sway
(reduced stability) evident across the mid-life period and subsequent decades. A three-way
interaction of age, support and visual condition was established, suggesting changes in
somatosensory and vestibular systems in particular were likely contributors to the reduced
stability in both mid-life and older decades and thus warranted further investigation1.
Whilst these findings were compelling, their translation into clinical or field use may be
limited when computerized (although portable) equipment was used to measure postural
stability. To address this, test conditions yielding failed trials - bilateral stance (foam EC)
and one-leg stance (firm surface, EO and EC) - were further investigated. Three categoriesof stability were investigated for participating women: stable (no failed trials), unsteady (1
or 2 failed trails) and unstable (failed all trials) categories. Differences in demographics
were revealed between the categories with those classified as unsteady and unstable
presenting with multiple risk factors for falls: older women, reporting more medical
conditions, more medications, more falls and less activity compared to those categorized as
stable. For foam (EC) and one-leg stance (firm EO) a low failure rate in mid-life and older
age decades was recorded whereas a high failure rate for one leg stance (firm EC) was
recorded in all decades (>25%), suggesting that this task was less able to differentiate
stability between decades when failed trials were considered. Thus it was recommended
that the sensori-motor causal factors associated with instability in bilateral stance (foam EO
and EC) and on one-leg (firm EO) warranted further investigation as these tests may have
potential as screening tools for instability from the mid-life and thus identify those who
may benefit from referral for pre-emptive education and intervention to foster healthier
ageing2.
The second major cross-sectional study was undertaken to investigate postural stability,
functional balance and mobility as well as possible contributing demographics and sensorimotor
factors in 320 healthy women aged 20 to 80 years. Pathology likely to contribute to
postural instability was again excluded. Age-related changes in postural stability were
confirmed for the study cohort while investigations of underlying sensori-motor factors
revealed that lower limb strength, vision, vestibular function and somatosensation all
reduced with increasing age, but that earlier significant reductions were evident in vision
and somatosensation (by the 40s or 50s) compared with vestibular function (by the 60s) and
strength (by the 70s). Associations between demographics and sensori-motor factors and
each postural stability and functional balance and mobility measures within each age
decade were investigated. Findings were used to develop a rationale for the delivery and
advocacy of functional weight-bearing programs that target both sensory and muscular
systems to improve stability during mid-life and into older decades to foster healthier
ageing3.
In the final study, demographics, functional task performances, strength and sensory system
function were compared between those categorized as stable, unsteady and unstable whenstanding on foam (EC) and on one-leg (firm, EO). Those categorized as unsteady or
unstable were older, used more medications, reported more co-morbidities and were less
active than stable women. They performed less ably on functional balance tests, and
showed reduced lower limb muscle strength, somatosensation and vision compared with
those classified as stable4.
The studies presented in this thesis provide support for the premise that postural stability
deteriorates across the lifespan and that demographic and sensori-motor factors may
explain earlier reductions in postural stability during mid-life for some women. This earlier
reduction in postural stability highlights the need for public health initiatives that identify
early deterioration in postural stability and associated demographic and sensori-motor risk
factors for falls. To begin to address this issue, the studies presented here have identified
simple clinical measures of postural stability that may be further developed as screening
tools to identify women who may need a more detailed investigation of falls risk factors.
The evidence is used to support rationale for targeting the sensory and muscular systems for
exercise based pre-emptive interventions during mid-life and into older decades for
healthier ageing.
Additional Notes 13 Colour pages 46, 150, 152, 154-155, 157-158, 160-163. 30 Landscape Pages: 57-58, 65, 67, 71, 82, 88, 90, 177, 188, 209, 220, 223-224, 252, 272, 341-342, 428-429, 431-433, 439, 445, 448-452.

 
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Created: Mon, 03 Nov 2008, 13:50:10 EST by Mrs Nancy Low Choy on behalf of Library - Information Access Service