Hearing loss and Alzheimer?s disease: A Review

Abstract

Many studies have focused on the relationship between hearing loss and Alzheimer's Disease (AD). The mechanisms and causal relationship of this association are still partially unknown, and several theories have been proposed. The most accredited hypothesis is that peripheral hearing deprivation may lead to social isolation and subsequently to dementia. Another hypothesis supports the role of hearing loss on cortical processing, with an increased assignment of cognitive resources to auditory processing rather than to other cognitive processes; other theories suggest changes in the brain structure following reduced peripheral auditory stimulation, or a common cause to both conditions. These preliminary findings clearly delineate the importance of further research aimed at investigating hearing impairment in AD, to a) allow early detection of people with predisposition to AD, b) improve the quality of life in AD patients with hearing loss and c) possibly prevent the progression of the disease treating the hearing impairment. In this review paper, the authors discuss current evidence on the association between hearing impairment and dementia, the identification of peripheral and central auditory dysfunction in at-risk patients as a potential early indicator of incipient AD, and the clinical aspects and the management of patients with AD and hearing loss.

A Novel Score for Predicting Alzheimer’s Disease Risk from Late Life Psychopathological and Health Risk Factors

“…In line with the literature, we found a higher incidence of AD in subjects with hearing loss. It has been widely associated in the literature with the risk of AD [51] and all-cause dementia [52], and several hypotheses about such causal relationship have been proposed. Among them, it is hypothesized that it could lead to social isolation, and this to dementia [51].…”

“…It has been widely associated in the literature with the risk of AD [51] and all-cause dementia [52], and several hypotheses about such causal relationship have been proposed. Among them, it is hypothesized that it could lead to social isolation, and this to dementia [51]. In addition, it has been shown that the genetic risk of AD also influences the hearing of speech in noise, without these hearing deficits being related to further cognitive impairment [53].…”

Exploring the genetic relationship between hearing impairment and Alzheimer's disease

“…Several other theories have been proposed to explain the association between hearing impairment and AD. Hearing impairment has been proposed as a risk factor for AD through mediating pathways such as sensory deprivation and social isolation leading to decreased cognitive function 15,50,51 and an increased cognitive load through auditory processing rather than other cognitive processes 52,53 . This decreased auditory stimulation may lead to micro‐changes in the brain that increase risk of AD brain pathology, such as amyloid decomposition 18 .…”

“…This decreased auditory stimulation may lead to micro‐changes in the brain that increase risk of AD brain pathology, such as amyloid decomposition 18 . An alternative hypothesis is that the relationship between these two traits may be due to a common cause, such as shared genes or age‐related changes in the brain, and that hearing impairment may be an early symptom of cognitive decline 2,53 …”

Noise Induced Hearing Loss and Tinnitus—New Research Developments and Remaining Gaps in Disease Assessment, Treatment, and Prevention

“…Several recent review studies have emphasized the maladaptive plasticity of NIHL, covering detailed neuronal aspects of triggers of tinnitus, mechanisms underlying generation of tinnitus in the cochlear nucleus after noise-induced deafferentation, likely routes of transmission of tinnitus signals along the ascending nuclei, as well as treatment approaches to reduce the impact of tinnitus on the quality of life of affected individuals [ 21 , 36 , 37 , 38 , 39 ]. A general consensus is that NIHL is preventable and that there is much more to learn about tinnitus and its underlying mechanisms and undisputed connection with NIHL.…”