The effect of ageing on vestibular control of balance

跌倒是老年人的一大问题。大约30%的65岁以上的人每年经历一次或多次跌倒，80岁以后这一比例上升到50%。10-15%的跌倒会导致严重伤害，每年给NHS和社会服务造成高达10亿英镑的损失。人口老龄化只会加剧这一问题。各种因素，如肌肉无力和感觉丧失，都与摔倒的风险增加有关，但尽管问题严重，我们对摔倒的潜在机制知之甚少。前庭系统位于内耳，在保持平衡方面起着重要作用。前庭反馈告诉我们头部是如何在空间中移动的，这些信息被用来减少姿势摇摆。因此，前庭反射在阻止跌倒中很重要。然而，为了使它们正常工作，需要将信息从以头部为中心的参考框架转换为以身体为中心的参考框架。这需要精确的头部方向感，也需要中枢神经处理。这些因素随着年龄的增长而退化，这可能导致不准确或缺失的反应，导致姿势不稳定和跌倒。这将通过评估不同年龄组使用前庭信息控制平衡的能力来进行测试。前庭神经的电刺激会引起头部运动的感觉。这是一种无痛的技术，对站立的受试者产生可靠的摇摆反应。摇摆反应的准确性将在年轻（18-40岁）、中年（40-65岁）和老年（50 -65岁）受试者中进行评估。这将决定年龄对利用前庭信息保持平衡能力的影响。志愿者还将通过一系列感觉运动测试和问卷调查来评估跌倒风险。这将揭示前庭平衡控制和跌倒风险之间的联系。前庭反应改变的原因也将被调查。具体来说，感觉头部方向的能力，以及周围前庭器官的完整性，都将被测试。这种多因素的方法将提供一个全面的画面，从前庭控制改变的原因，到姿势稳定和跌倒的后果。这项研究对识别高危人群以及设计运动和治疗方案以降低风险具有重要意义。在人口老龄化的情况下，这一点变得越来越重要。

Falls are a major problem for the elderly. Approximately 30% of people aged over 65 experience one or more falls per year, rising to 50% after 80. 10-15% of falls result in serious injury, costing the NHS and social services up to £1billion annually. This problem can only be exacerbated by an ageing population. Various factors such as muscle weakness and sensory loss have been associated with increased risk of falling, but despite the magnitude of the problem, we know little about mechanisms underlying falls. A structure which is known to play an important role in maintaining balance is the vestibular system, which resides in the inner ear. Vestibular feedback tells us how the head is moving in space and this information is used to reduce postural sway. Vestibular reflexes are therefore important in arresting falls. However, for them to work properly requires the information to be transformed from a head-centred to a body-centred frame of reference. This requires a precise sense of head orientation, and also central neural processing. These factors are known to degrade with age and this may cause inaccurate or absent responses, leading to postural instability and falls. This will be tested by assessing the ability of different age groups to use vestibular information for controlling balance. Electrical stimulation of the vestibular nerve will be used to induce a sensation of head movement. This is a painless technique which produces reliable sway responses in standing subjects. The precision of the sway response will be assessed in young (18-40), middle aged (40-65) and elderly (>65) subjects. This will determine the effect of age upon the ability to use vestibular information for balance. Volunteers will also be assessed for fall risk, using a series of sensory-motor tests, and a questionnaire. This will reveal any link between vestibular control of balance and the risk of falling. Reasons underlying altered vestibular responses will also be investigated. Specifically, the ability to sense head orientation, and the integrity of the peripheral vestibular apparatus, will both be tested. This multi-factorial approach will provide an overall picture, from the reasons underlying altered vestibular control, to the consequences for postural stability and falls. This research has implications for identifying individuals at high risk of falling, and for designing exercise and therapy programmes for reducing risk. This is becoming increasingly important in our ageing population.