Vestibular impairment, cognitive decline and Alzheimer's disease: balancing the evidence.

The vestibular (inner ear balance) system senses head movement and orientation in space. Vestibular sensory input plays a critical role in spatial cognitive abilities such as spatial memory and spatial navigation. Vestibular function declines with age, and recent studies have shown that age-related vestibular impairment is associated with poorer spatial cognitive skills in healthy older adults. Moreover, vestibular impairment is disproportionately prevalent among individuals with mild cognitive impairment and Alzheimer's disease, and specifically in cognitively-impaired individuals who have spatial deficits such as disorientation and difficulty driving. Indeed, emerging evidence suggests that age-related vestibular impairment contributes to a 'spatial' subtype of Alzheimer's disease, characterized by highly morbid symptoms such as wandering and falls. Given that vestibular impairment can be treated through simple, physical-therapy based exercises, identifying and treating vestibular deficits in older adults with and without cognitive impairment may offer substantial benefit in preventing, mitigating and forestalling cognitive decline.