A number of different studies not only in the US but Europe as well, have found a significant correlation between hearing loss and dementia. It’s hard to say for sure what the cause of this correlation is. Some studies suggest that hearing loss reduces brain stimulation important to the health of the brain, other studies, particularly at John’s Hopkins suggests there may be a common cause, such as a lack of antioxidants or a magnesium deficiency such that, a lack of these in the brain not only impair the brain but hearing as well. And there is the more obvious possibilities that if the cognitive or memory test is oral, subjects may not hear the instructions or words they are asked to recall well, which of course could affect their scores.
The one thing we do know now, is that hearing aids appear to have a protective effect such that, wearing appropriate hearing aids, for those who need them, can improve memory and reduce the risks for dementia to a significant extent.
Using hearing aids can lower the risk of developing dementia for people with hearing loss. Several major studies have found that people with hearing loss who do not use hearing aids have a 1.7% risk of dementia, while using a hearing aid reduces the risk to 1.2%2. Another clinical trial showed a 48% reduction in risk among participants at higher risk of dementia.