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Abstract

Mobility impairments are extremely common in older age, often resulting in loss of
independence, reduced social participation and injuries from falls. As well as reduced
quality of life, these outcomes produce significant medical and residential care costs for the
individual and for society. With the rapid ageing of populations, there is an urgent need to
identify risk factors to prevent mobility decline and associated problems.
This thesis aims to examine associations between age and walking performance, their
relationships to the sensorimotor factors that may contribute to walking impairments, and
finally to identify measures of walking performance that increase the risk of falling.
In studies of population-based samples of community dwelling older adults (60-86 years),
greater age was associated with poorer performance in gait speed, step length, double
support phase and step width among persons of each sex, and additionally with slower
cadence among women. Among men the associations were linear. For women, stronger
associations were found among those of greater age. Gait variability measures (the
fluctuation in a gait measure from one step to the next) were also examined. Apart from
step time variability, for which stronger associations were seen for older women, greater
variability in gait measures was linearly associated with greater age.
In further studies of the same population, poorer performance on a range of sensorimotor
factors was associated with impaired gait speed, step length, cadence, double support phase
and step width, and with greater gait variability. Quadriceps strength explained the
greatest proportion of variance for the majority of average measures of gait, whereas
postural sway measured with eyes closed standing on a foam mat explained the greatest
proportion of variance for gait variability. Differences in the pattern of associations
between the sensorimotor factors and average measures of gait were seen for men and
women.
Information on falls was collected prospectively over a 12 month period. Greater step
length variability and double support phase variability were linearly associated with
increased risk of multiple falls, whereas gait speed, cadence and step time variability were
non-linearly associated with increased risk of multiple falls. None of the gait measures
predicted risk of single falls. In conclusion, this series of related studies add considerably to knowledge about age-related
changes in walking, and to understanding of gait measures and sensorimotor factors
that may be targeted to prevent walking impairment and loss of independence in older age.
Specific gait measures which may be useful in identifying those at risk and used as
outcome measures in intervention programs to reduce falls risk, have been identified.

Item Type:	Thesis - PhD
Authors/Creators:	Callisaya, ML
Keywords:	Older people, Gait disorders in old age.
Copyright Holders:	The Author
Copyright Information:	Copyright 2010 the Author - The University is continuing to endeavour to trace the copyright owner(s) and in the meantime this item has been reproduced here in good faith. We would be pleased to hear from the copyright owner(s).
Additional Information:	Chapter 4 is the equivalent a pre-copyedited, author-produced PDF of an article accepted for publication in the Journal of gerontology : medical sciences following peer review. The version of record, Callisaya, M. L.; Blizzard, L; Schmidt, M.D.; McGinley, J. L; Srikanth, V. K., 2008, Sex modifies the relationship between age and gait : a population-based study of older adults, Journal of gerontology : medical sciences, 63(20), 165-170, is available at: http://biomedgerontology.oxfordjournals.org/content/63/2/149.full Chapter 5 is the equivalent a pre-copyedited, author-produced PDF of an article accepted for publication in Age and ageing following peer review. The version of record, Callisaya, M. L.; Blizzard, L; Schmidt, M.D.; McGinley, J. L; Srikanth, V. K., 2010, Ageing and gait variability—a population-based study of older people, Age and ageing, 39, 191-197, is available at: http://dx.doi.org/10.1093/ageing/afp250 Chapter 6 is the equivalent a pre-copyedited, author-produced PDF of an article accepted for publication in Age and ageing following peer review. The version of record, Callisaya, M. L.; Blizzard, L; Schmidt, M.D.; McGinley, J. L; Lord, S. R.; Srikanth, V. K., 2009, A population-based study of sensorimotor factors affecting gait in older people, Age and ageing, 38(30), 290-295, is available at: http://dx.doi.org/10.1093/ageing/afp017 Chapter 7 is the equivalent a pre-copyedited, author-produced PDF of an article accepted for publication in the Journal of gerontology : medical sciences following peer review. The version of record, Callisaya, M. L.; Blizzard, L; McGinley, J. L; Schmidt, M.D.; Srikanth, V. K., 2010, Sensorimotor factors affecting gait variability in older people : a population-based study, Journal of gerontology : medical sciences, 65A(4), 386-392, is available at: http://dx.doi.org/10.1093/gerona/glp184
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