Does hearing loss increase your risk of dementia, and does a hearing aid help?

Hearing loss is consistently associated with a higher risk of dementia. In a large cohort study of more than 573,000 people, the risk among those with hearing loss was somewhat higher than among people with normal hearing (hazard ratio 1.07). A meta-analysis of 36 studies involving more than 20,000 participants found an odds ratio of 1.28 for dementia. The association is modest but robust. Epidemiological models estimate that hearing loss in middle age is responsible for approximately 9% of all dementia cases worldwide, making it one of the larger modifiable risk factors.

The more severe the hearing loss, the greater the risk. For every additional 10 decibels of hearing loss, the risk increases by a factor of 1.27. In cases of severe hearing loss, estimates are even higher, but those figures come from small studies and are therefore uncertain. Hearing impairment also proved to be a risk factor for dementia occurring before the age of 65, so the association is not confined to the very elderly.

Exactly how hearing loss contributes to dementia remains unknown. Researchers point to several possible mechanisms: shared brain pathology, cognitive overload when trying to understand speech, and an information-poor environment that provides less stimulation to the brain. Which mechanism carries the most weight also determines how large the benefit of a hearing aid can realistically be.

The findings on hearing aids are mixed. In a large Danish cohort study, people with hearing loss who wore a hearing aid had a clearly lower risk than those who did not (hazard ratio 1.06 versus 1.20). However, the only large randomised trial to date, involving 977 participants aged 70 to 84, found no significant difference in cognitive decline over three years in the overall group. Only among older adults who already had more dementia risk factors was there an indication of a beneficial effect. A hearing aid is therefore not a proven means of preventing dementia, although there are indications that it may help people at higher risk.

Apart from dementia, there are other reasons to address hearing loss. It is associated with social isolation, late-life depression, falls and a generally reduced resilience. If you are experiencing hearing loss, it is certainly worth having it assessed, even if the dementia benefit of a hearing aid has not yet been established.