Wearing a hearing aid may delay the onset of dementia by slowing brain ageing by eight years, scientists believe.
In recent years, several studies have shown a link between hearing loss and neurodegenerative diseases like Alzheimer’s, but it was unclear whether deafness was a symptom of the illness or one of the causes.
Now a study of thousands of over-50s has found that wearing a hearing aid appears to protect against the long term brain decline, suggesting that becoming deaf can actually bring on, or speed up dementia.
Scientists now think that hearing loss may trigger brain damage elsewhere, and also stop people from socially interacting, which is known to protect the brain from cognitive decline.
“The mechanism for a connection between hearing loss is still uncertain. It could be biological or more social,” said Professor Clive Ballard, of the University of Exeter Medical School, who carried out the research with researchers at King’s College London.
“One hypothesis is that when the sensory nerve cells involved in hearing become dysfunctional it leads to dysfunction in the other nerves they interact with in the brain and that this may then slowly spread in a cascade effect.
“Another suggestion is that hearing loss contributes to social isolation or depression, which we know are risk factors for dementia.”
In the 24 month study, people were asked to take cognitive tests to assess their working memory and concentration.
After two years, the 1,557 partially deaf people who used the devices were able to focus better than the 2,815 who reported hearing loss but did not use an aid. Those without an aid had the concentration ability of someone eight years older.
Dr Anne Corbett, from the University of Exeter, said: “Previous research has shown that hearing loss is linked to a loss of brain function, memory and an increased risk of dementia.
“Our work is one of the largest studies to look at the impact of wearing a hearing aid, and suggests that wearing a hearing aid could actually protect the brain.
“We now need more research and a clinical trial to test this and perhaps feed into policy to help keep people healthy in later life.”
Experts said the findings were ‘exciting’ and suggested that making sure people had hearing aids in later life could have a huge impact on delaying dementia for thousands of older people.
However others said the study may show that helping older people to become more socially active is the driving force behind the finding.
Dr Llwyd Orton, Lecturer in Neurophysiology, Manchester Metropolitan University, said: “A reason hearing aids may work in this patient group is that losing hearing function later in life is socially isolating, while younger people develop sign language and social groups where communication is not dependent on sound.
“Another consideration is that the majority of people who are fitted for hearing aids, do not wear them correctly.
“This may lead to selection biases in studies such as these, including socioeconomic factors, due to the high cost of hearing aids and personal issues, such as embarrassment, which are common.”
Dr Martin Coath, Associate Lecturer, Plymouth University, added: “Hearing loss is a type of social isolation as, for example, it can make following conversations in a noisy room a struggle.
“Those with hearing issues who choose to use high-quality hearing aids are likely to continue to enjoy social experiences and conversations whereas those who do not use a hearing aid may choose to experience fewer social and sensory interactions as they are more challenging.”
Commenting on the research, Dr Jana Voigt, Head of Research at Alzheimer’s Research UK, added : “This is an exciting result that will need to be further tested in clinical trials, and if shown to work, encouraging people to wear hearing aids could be a simple but effective way of reducing dementia risk.”
The new research was presented at the Alzheimer’s Association International Conference in Los Angeles.