Longevity Briefs: Understanding The Link Between Dementia And Hearing Loss

Longevity briefs provides a short summary of novel research in biology, medicine, or biotechnology that caught the attention of our researchers in Oxford, due to its potential to improve our health, wellbeing, and longevity.

Why is this research important: There is a well established link between hearing loss and dementia. Recent evidence suggests that those with mid-life hearing loss are up to five times more likely to develop dementia later on compared to those with normal hearing. While the ears transform sound waves into electrical signals, it is the brain that processes these signals and allows us to perceive and understand sounds. Brain regions involved in this processing may be affected in the early stages of dementia, leading to hearing problems that could serve as an early warning for disease.

One characteristic hearing problem associated with dementia is the ‘cocktail party effect’, in which a person struggles to extract specific information from a noisy environment. For example, they may struggle to understand what their friend is saying at a cocktail party while ignoring the other conversations happening in the background.

What did the researchers do: In this study, researchers tested the ability of Alzheimer’s patients to extract and locate the source of sounds within noisy environments when compared to healthy older individuals. They used MRI (magnetic resonance imaging) to study brain structure and function in these individuals. They also studied whether donepezil, a medication for memory loss in Alzheimer’s disease, could help improve Alzheimer’s patients’ understanding of speech that was ‘degraded’ by mixing it with noise.

Key takeaway(s) from this research: People with Alzheimer’s disease found it harder to make sense of noisy environments. However, individuals who received a single dose of donepezil showed improved understanding of degraded speech.

These findings further support the importance of the link between hearing and dementia. That a drug aimed at improving memory can treat associated hearing problems suggests that there are common pathways in the brain which can be targeted to treat both processes. Further research into these pathways might lead to better treatments. This research also highlights the potential for using complex hearing tests to detect early signs of dementia.

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