What does age-related hearing loss have to do with dementia?

In addition to the impacts on your emotional well-being, untreated hearing loss can also affect your cognitive health.

In the last decade, a growing body of research has shown an independent association between age-related hearing loss and dementia. Meaning that people with hearing loss are more likely to develop cognitive problems than people who do not have hearing loss.

Although this doesn't imply that everyone with age-related hearing loss will necessarily develop dementia, the research shows that:

Dementia is more common among people with hearing loss.
The incidence of dementia among people with hearing loss increases with greater hearing loss
People with hearing loss tend to develop cognitive decline earlier than peers with normal hearing
People with hearing loss report more concerns about their memory than people with normal hearing

The mechanisms underlying the association between age-related hearing loss and dementia are unclear. There are several theories explaining the hearing-cognition relationship:

Depletion of Cognitive Reserve - Hearing loss appears to potentially affect cognitive reserve. Studies have demonstrated that individuals with hearing loss dedicate more neural resources to facilitate auditory processing at the expense of other cognitive processes, such as working memory.
Social Isolation - Hearing loss is associated with increased social isolation in older adults, likely through impaired communication. Studies have demonstrated that poor social networks, reduced social support, and loneliness increase the risk of incident dementia in initially disease-free individuals.
Changes in Brain Structure - Another hypothesis is that age-related hearing loss may induce detectable changes in brain structure, which may, in turn, increase the risk of dementia.
Common Mechanisms - It is also possible that age-related hearing loss itself does not cause dementia; instead, a common mechanism underlies both dementia and age-related hearing loss. For example, a microvascular disease can cause insufficient blood flow to both the inner ear and the brain leading to hearing loss and cognitive decline simultaneously.