Date of Award

Spring 2003

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biomedical Engineering

First Advisor

Charles J. Robinson

Abstract

Research objectives. One source of falls in the elderly may be an inability to sufficiently adjust to transient postural perturbations or slips. Identifying useful predictors of fall potential, as well as factors that affect the ability of an individual to detect a movement of the standing support surface may provide insight into postural stability and methods to increase stability in elders. To do this, acceleration thresholds to short, precise, lateral platform translations and the resultant psychophysical responses of adults with early Type 2 diabetes to age-matched controls and young adults were measured.

Methods. Using an innovative SLIP-FALLS platform, short (1, 2, 4, 8,and 16mm) lateral perturbations were presented to 21 individuals—9 young adults, 6 neurologically intact elder adults, and 6 elders with diabetes using a two-alternative forced choice (2AFC) protocol. All subjects underwent lower-limb nerve conduction velocity determination, air conduction velocity testing, Semmes-Weinstein monofilament thresholds, the Mini Mental Status Exam, and reaction time tests to touch, tone and high acceleration, 4mm super-threshold perturbations.

Results. All three groups had significantly different thresholds at all small (<4mm) movement lengths, with the diabetic neuropathy group having a markedly higher acceleration threshold (P < 0.001); the healthy elderly, which, in turn, had markedly higher thresholds than young adults. Patients with neuropathy had significantly higher reaction times to platform movements and touches to the plantar sole, but not for auditory tones. Both elderly groups had a significantly higher reaction time to superthreshold platform movement than did young adults. Sensory tests revealed slower nerve conduction velocities, higher air conduction velocities, and lower cognitive ability in the diabetic group.

Conclusions. A marked decrease in perception of very small moves due to aging and diabetic neuropathy could well have a detrimental effect on postural control mechanisms. The higher prevalence of falls in the elderly and elderly diabetics may be due to decreased perceptual ability, slower nerve conduction velocities, and slowing reaction times compounded by larger amounts of imparted energy needed for detection of a slipping event.

Download

Share

COinS