What is the Relationship Between Hearing Loss and Alzheimer's Disease?
Age-related hearing loss correlates with the risk of onset and progression of neurodegenerative conditions such as Alzheimer's disease. There is some question as to whether this correlation exists because similar processes of neurodegeneration produce both outcomes, or whether one drives the other, or whether there is a bidirectional relationship. It seems plausible that reduced sensory input can accelerate decline of neural networks that run on a "use it or lose it" basis, though current thinking is also focused on reduced quality of sensory input causing functional issues in neural processing. Either way, the question remains as to whether that can account for a meaningful fraction of the loss of cognitive function and related issues, versus other more blunt mechanisms, such as the chronic inflammation in brain tissue that is characteristic of neurodegenerative diseases.
Evidence suggests that hearing loss (HL), even at mild levels, increases the long-term risk of cognitive decline and incident dementia. Hearing loss is one of the modifiable risk factors for dementia, with approximately 4 million of the 50 million cases of dementia worldwide possibly attributed to untreated HL. This paper describes four possible mechanisms that have been suggested for the relationship between age-related hearing loss (ARHL) and Alzheimer's disease (AD), which is the most common form of dementia.
The first mechanism suggests mitochondrial dysfunction and altered signal pathways due to aging as a possible link between ARHL and AD. The second mechanism proposes that sensory degradation in hearing impaired people could explain the relationship between ARHL and AD. The occupation of cognitive resource (third) mechanism indicates that the association between ARHL and AD is a result of increased cognitive processing that is required to compensate for the degraded sensory input. The fourth mechanism is an expansion of the third mechanism, i.e., the function and structure interaction involves both cognitive resource occupation (neural activity) and AD pathology as the link between ARHL and AD.
Exploring the specific mechanisms that provide the link between ARHL and AD has the potential to lead to innovative ideas for the diagnosis, prevention, and/or treatment of AD. This paper also provides insight into the current evidence for the use of hearing treatments as a possible treatment/prevention for AD, and if auditory assessments could provide an avenue for early detection of cognitive impairment associated with AD.
Anyone know if wearing hearing aids attenuates the dementia associated with hearing loss? This would seem to be a way to test whether we're looking at causation or correlation.