An examination of the relationship between gait, cognition and risk of falling in an older population based sample

Falls are a significant public health problem for older people. Their prevention is important to reduce hospital admissions, and related loss of independence, morbidity and mortality. They have multiple risk factors, including impaired cognitive function and gait deterioration. Inter-relationships between cognitive function and gait in contributing to falls are poorly understood, with few data from population-based studies. This thesis aimed to examine the associations between cognitive function, gait and the risk of falling in a series of studies conducted in a population-based sample of older people aged 60-86 years. Cognitive functions were assessed from a battery of tests. Gait was assessed using the GaitRite walkway and a force platform. Falls-risk was assessed using the Physiological Profile Assessment, and falls were recorded prospectively using a 12-month diary. In the first study, measurements of GI using the GaitRite walkway were compared with those on the same 28 subjects measured using a 200Hz force platform, considered to be the gold standard. The GaitRite walkway measurements had higher systematic error and inferior predictive validity for falls-risk. In the second study, poorer processing speed and executive function/attention, but not deficits in memory or visuospatial ability, were independently associated with poorer gait. Deficits of processing speed, executive function and visuospatial ability were associated with increased intra-individual gait variability in double support phase, a measure of balance during gait. In the third study, time to first lateral movement could be the best measure of gait initiation, given its consistent associations with surrogates of falls-risk and cognition, while also being most responsive to cognitive interference from dual-tasking. In the fourth study, executive function, processing speed and visuospatial ability, but not memory, were independently associated with a surrogate measure of falls-risk.In the final study, poorer executive and visuospatial functions predicted the risk of multiple falls. The associations between all cognitive functions and the risk of multiple falls were magnified in those with poorer sensorimotor function, gait speed or ambulatory activity. These studies add significantly to knowledge about the relationships between cognitive functions, gait and the risk of falling, in community-dwelling older people. Consistent with prior studies, executive function and processing speed may either be involved in gait control or share the same neural substrate. Visuospatial ability, a higher cortical function reflecting sense of space and position, was associated with gait. Memory appeared to have the least influence. Cognitive function and physical sensorimotor impairments were found to interact in predicting multiple falls, suggesting that brain reserve capacity plays a role in compensating for physical frailty in older people. Lastly, these data substantially add to the issue of the choice of measure of gait initiation, and will guide future studies in this field