| Summary: | The prevalence of obesity is high in the United States. One of the many concerns with the high prevalence of obesity is its association with an increased risk of falls and subsequent injury. Thus, it is important to understand factors affecting falls among individuals who are obese, to help develop effective intervention solutions to mitigate falls in this population. Obese individuals have been hypothesized to have an impaired plantar sensitivity, and this may influence their balance control, thus lead to more falls. Executive function deficits in individuals who are obese may affect their ability to allocate attentional resources to dual tasks (walking while performing other tasks), and may put them at higher risks of falls. Gait alterations and muscle strength deficits in individuals who are obese may also increase their fall risks. Therefore, three studies were carried out to provide better understanding into the factors affecting falls in individuals who are obese.
The first study investigated the effects of obesity on plantar sensitivity, and explored the relationship between plantar sensitivity and postural sway during quiet standing. Plantar sensitivity was measured as the force threshold at which an increasing force applied to the plantar surface of the foot was first perceived, and the force threshold at which a decreasing force was last perceived. Measurements were obtained while standing, and at two locations on the plantar surface of the dominant foot. Postural sway during quiet standing was then measured under three different sensory conditions. Results indicated less sensitive plantar sensitivity and increased postural sway among individuals who are obese, and statistically significant correlations between plantar sensitivity and postural sway that were characterized as weak to moderate in strength. As such, impaired plantar sensitivity among individuals who are obese may be a mechanism by which obesity degrades standing balance among these individuals.
The second study investigated the influence of obesity on executive function, and determined whether there is a relationship between executive function and fall risk (as estimated from selected gait parameters). Four major components of executive function were assessed, including selective attention, divided attention, semantic memory and working memory. Both single- and dual-task walking (walking-while-talking) were completed to evaluate fall risk during gait. Less effective selective attention, semantic memory, and working memory were found among young obese adults. Participants exhibited higher fall risks during dual-task walking, and executive function scores were associated with gait during dual-task walking. In conclusion, obese individuals exhibited less effective executive function, which may be associated with their increased fall risk.
The third study explored differences in gait, plantar sensitivity, executive function, lower extremity muscle strength, and body size between fallers and non-fallers, and the strength of the association between the same factors and slip severity. Participants' gait, plantar sensitivity, executive function, lower extremity muscle strength, and body size measures were obtained. An unexpected slip was introduced in a laboratory setting to obtain slip severity related measures and slip outcome. Results indicated obese fallers exhibited better executive function (selective attention), stronger lower extremity muscle strength, lower BMI and smaller waist circumference. Results also indicated increased slip severity was associated with faster walking speed, longer step length, higher RCOF, worse executive function (working memory), and lower BMI. Slower reactive recovery response was also associated with lower BMI. As such, better selective attention and stronger muscle strength exhibited limited benefit in slip recovery among individuals who are obese. Altered gait pattern, and working memory may be factors by which obesity increased slip severity, and lower BMI among individuals who are obese may increase slip-induced fall risks.
In conclusion, reduced plantar sensitivity, impairments in executive function, altered gait pattern were associated with deficits in standing and walking balance control, and increased slip severity among individuals who are obese. Therefore, appropriate fall prevention/intervention program targeting at some or all of these factors may be considered as solutions to decrease fall risks for obese individuals. === Ph. D.
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