According to the Lancet Commission on Dementia Prevention and Care report, age-related hearing loss is the most significant modifiable risk factor for dementia. It has also been suggested that hearing loss in midlife accounts for approximately 8.2% of all dementia cases. Research has shown that by age 72, one in three US adults has lost some of their hearing. However, more than 80% failed to seek treatment.
Unfortunately, experts say it remains unclear as to why hearing loss affects the risk of dementia. There are many causes for dementia, but many potential mechanisms link hearing loss to a decline in brain health. More than one factor may be causing dementia as people age.
Some experts believe that the same disease process causing hearing to deteriorate is also harming cognition. For example, small strokes that cause vascular dementia may be affecting the inner ear. Hearing loss decreases activity in key regions of the brain responsible for thinking which could also lead to an increase in neurodegeneration.
“It could be there’s a boosting effect on the brain from being able to hear, which allows you to better process auditory signals and experience speech and communication and emotional communication,” said Timothy Griffiths, a professor of cognitive neurology at Newcastle University in Newcastle Upon Tyne, England.
“Impoverished input leads to impoverished brain reserve, so that leads to a higher risk for dementia.”
A large number of studies have also suggested that listening under challenging conditions can make it harder to carry out other tasks that require more attention. The brain needs to use more effort to listen to things, and that brain effort is taking away from the resources that may be needed for other activities.
With so many studies suggesting that hearing loss is linked to dementia, researchers are still unclear whether treating the hearing loss would slow or stop the progression of dementia. There is evidence that hearing aids may protect people with hearing loss and mild cognitive impairment from further decline, but this data has been mixed and needs more clinical research.
However, researchers stress that using a hearing aid should be encouraged as it can only help, not harm, those with hearing loss. The Lancet Commission report also promotes the use of hearing aids to help lower the risk of dementia.
Hearing loss has also been shown to make it harder for people to socialize. Yet, social isolation has been shown to raise the risk of dementia by roughly 50%. So, using a hearing aid can help to reduce social isolation and therefore cut the risk of dementia.