How does hearing loss affect the brain?

This type of 'effortful listening' is associated with increased stress responses, changes in pupil dilation, and poorer behavioral performance (e.g., on memory tests for degraded speech). It is thus possible that even a mild-to-moderate hearing loss can inflate the appearance of cognitive decline in the older adult – a cautionary note for the geriatric clinician/diagnostician and family members alike. This sensory–cognitive interaction is a reminder that the auditory system may be the conduit to the brain, but it is the brain that 'hears' [6]. The connection between hearing acuity and cognition, however, may go beyond the effects of competition for limited resources under conditions of effortful listening. A striking finding from a recent large-scale population study has revealed a strong statistical connection between the appearance and degree of hearing loss and all-cause dementia [7]. Indeed, as Lin and colleagues have shown, this relationship persists even when adjusted for sex, age, race, education, diabetes, smoking history and hyper tension [8]. This statistical relationship does not in itself establish causation, such as whether continuous perceptual effort with hearing loss takes a cumulative toll on cognitive reserves, whether the cognitive decline is consequent to depression and social isolation that can often accompany a serious hearing loss, or whether the parallel incidence of reduced hearing acuity and the appearance of dementia are independent reflections of an aging nervous system. It is also possible that all of these factors may be contributing to the relationship between hearing acuity and demen-tia to some degree. It is the case, however, that these findings join others that have begun to show a statistically reliable association between auditory processing deficits and the appearance of cognitive decline [9]. Although the relationship between hearing loss and cognitive ability must be rooted in the brain, only recently have cognitive neuroscientists begun to explicitly examine the neurobiological bases for these effects. A recent pair of studies using MRI were aimed at precisely examining this link [10]. All Although estimates vary, some 40–50% of adults over the age of 65 years have a measure-able hearing impairment, with this figure rising to 83% of those over the age of 70 years [1]. These data make hearing loss the third most prevalent chronic medical condition among older adults, after arthritis and hypertension [2]. Beyond the obvious impediment to spoken communication , we have come to realize that there are also hidden effects of hearing loss that …