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

摘要 失去稳定性和跌倒是老年人受伤和死亡的主要危险因素。以前被忽视的是， 终生接触噪声已被证明会对前庭外周造成损害；尽管，动物模型 而人类研究可以提供一个机制基础，将噪音引起的前庭功能障碍和 与年龄相关的跌倒风险是有限的。前庭系统在检测头部运动和 与重力有关的方向，对正常视力和姿势控制是必不可少的。由于他们的 耳石器官在解剖上靠近耳蜗处，暴露在声压下，有可能受到噪音的威胁。 过度刺激，这可能导致前庭功能障碍。然而，损害可能不仅限于 耳石器官。最近的研究表明，噪音过度刺激与前庭神经活动减少和丢失有关。 属于一种特殊类别的不规则放电前庭传入，表现出对加速度的增强敏感性。 这些传入可能起着重要的作用，启动姿势补偿的突然变化 头部或身体位置与其生理特征及其向次级前庭的投射 投射到脊髓的神经元。因此，噪音的影响可能会加速与 自然老化。这项建议的目标是描述与自然衰老相关的前庭损失的特征以及如何 在人的一生中，累积的噪音暴露会加剧这种情况。因此，我们将系统地调查 寿命内噪声暴露对耳石和耳道结构和功能的影响(目标1)， 具体处理非正常传入损害的程度及其功能后果(目标2)，并评估 姿势、机动性和平衡随噪声暴露的变化(目标3)。感觉细胞突触的变化将 与前庭反射障碍和跌倒风险有关的姿势不稳定和丧失 平衡。为了更好地理解这些变化是如何在一生中发生的，我们将评估 成年早期、中期和晚期的解剖和功能变化。此外，功能实验将 在大鼠和人类参与者中并行进行，以最大限度地将我们的结果转化为临床。 单独来看，动物和啮齿动物的研究已经证明对我们理解噪音的影响是非常有价值的。 暴露于前庭功能。但是，这两种方法都有一些限制，这些限制可以通过一组 两个系统的免费学习。这项建议描述了一个全面的、多学科的 一种努力评估跌倒和跌倒风险增加的潜在机制的方法 老年人的噪音暴露。这些人对可能致命的跌倒的易感性突显了 需要一种系统的方法，这最终可以导致改进训练和康复方法 与这群人一起使用。

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. However, damage may not be limited to the otolith organs. 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 proposal is to characterize vestibular loss associated with natural aging and how it is compounded by cumulative noise exposures throughout one’s life. Thus, we will systematically investigate the effects of noise exposure across the lifespan on otolith and canal structure and function (Aim 1), specifically address the extent of irregular afferent damage and its functional consequences (Aim 2), and asses changes in posture, mobility and balance with noise exposure (Aim 3). Changes in sensory cell synapses will be correlated with vestibular reflex impairment and fall risk associated with postural instability and loss of balance. To improve our understanding of how these changes occur over the lifetime, we will assess anatomical and functional changes in early-, middle-, and late-adulthood. Further, functional experiments will be done in parallel in rats and human participants for maximal translation of our results to the clinic. Individually, both animal and rodent studies have proven invaluable to our understanding of the effects of noise exposure on vestibular function. However, both have limitations that can be best addressed with a set of complimentary studies in the two systems. This proposal describes a comprehensive, multidisciplinary approach that strives 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.