Effects of Noise Exposure Across the Lifespan on Balance and Stability in Older Adults

Veterans Education And Research Association Of Michigan, Ann Arbor MI

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Abstract

Abstract Loss of stability and falls is a major risk factor for injury and death in older adults. Previously overlooked, lifetime noise exposure has been shown to cause damage to the vestibular periphery; although, animal models and human studies that can provide a mechanistic basis connecting noise-induced vestibular dysfunction and age-related fall risk are limited. The vestibular system plays a critical role in detection of head movements and orientation with respect to gravity and is essential for normal vision and postural control. Due to their anatomical proximity to the cochlea, the otolith organs are exposed to sound pressure and are at risk for noise overstimulation, which may contribute to vestibular dysfunction. Recent studies have linked noise overstimulation to decreased vestibular nerve activity and loss of a specialized class of irregularly firing vestibular afferents which exhibit enhanced sensitivity to acceleration. It is likely that these afferents play an important role initiating postural compensation for abrupt changes in head or body position due to their physiological characteristics and their projection to secondary vestibular neurons that project to the spinal cord. Therefore, the effects of noise may accelerate disability associated with natural aging. The goal of this supplement is to purchase equipment to measure vestibular evoked myogenic potentials (VEMP) in human participants, and thus assess changes in otolith function associated with noise exposure. The inclusion of VEMP reflects Reviewer recommendation to use vestibular-evoked myogenic potentials to directly assess how noise exposure might affect otolith function in humans and compare to outcomes in the rat. The VEMP experiments will be performed in lieu of the dynamic tilt detection experiments proposed in the parent grant. VEMP testing can be done in the same, or shorter amount of time to assess otolith function under dynamic stimulation conditions. This supplement will allow us to incorporate a well-characterized physiological assessment in human subjects to evaluate the underlying mechanisms in increased falls and fall risk due to a history of noise exposure in older adults. The susceptibility of these individuals to potentially fatal falls underscores the need for a systematic approach, that can eventually result in improved training and rehabilitation methods to be used with this population.