The role of gait variability in ageing, frailty and the onset of cognitive decline. Exploring quantitative techniques for gait analysis

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• August 14, 2015
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The ability to walk is critical for the functional independence and well-being of elderly people. In this vein, musculoskeletal changes in the course of frailty syndrome impact on the functional status and affect the required strength in the lower extremities to maintain physical performance and, specifically, to preserve gait capabilities. Accordingly, frailty progression compromises gait performance. In the opposite direction, gait exercises are the most effective non-pharmacologic interventions to delay functional decline and to promote active ageing. Nevertheless, gait is more than a locomotor activity. It is a cognitive complexity task involving nervous system, muscle activation and joint movements, coordinated by the cognitive function, particularly, the executive function. Neurophysiological changes due to the effect of ageing, related to the presence of neurological pathologies (including neurodegenerative diseases) or as a result of cognitive decline affect gait capabilities. These gait changes are particularly visible in gait variability. In this Ph.D. Thesis we hypothesize in the opposite direction, asking ourselves how gait changes affect ageing and mental state. Traditionally, gait assessment has relied on the evaluation of average spatio-temporal parameters, such as the average stride intervals or average cadence. Captured variability within the human gait cycle has been defined as a white noise variation inherent to the data acquisition process. Considered as a set of uncorrelated fluctuations, gait variability has not been interpreted as an important piece of information about how the multi-level neural control and the musculoskeletal systems are involved to produce a consistent gait pattern and it has been discarded. However, this trend has shifted, highlighting the importance of gait variability assessment, as the number of publications demonstrating correlations between gait fluctuations have increased, also assisted by the improvements in the accuracy achieved by new Quantitative Gait Analysis techniques and the instrumentation used to demarcate gait events. This Ph.D. Thesis attempts to contribute to the development of Quantitative Gait Analysis systems focused on monitoring spatio-temporal parameters of human gait with special emphasis on assessing gait variability. Different prototypes are created prioritizing low-cost and easy-deployment policies and enabling gait trials more widely available. This Ph.D. Thesis also explores the associations between gait variability and ageing in frail elderly subjects; and the impact on mental state of gait variability and other commonly used characteristics in frailty assessment through two empirical experiments. The gait data required for the assessments comes from explicit gait trials performed while using one of the prototypes developed.