Hearing loss is very common in older adults. You probably know someone who suffers.

On average, based on studies in Australia, Europe and the US, it affects around 32 per cent of people aged 55 years old, and more than 70 per cent of people aged over 70 years.

But you may not know that hearing loss is independently associated with the rate of cognitive decline in older adults.

Research shows us that the rate of cognitive decline increases with the severity of hearing loss

Even for people with mild hearing loss, the rate of cognitive decline can be 30 to 40 per cent faster than for a person with normal hearing.

In fact, the reported risk of developing dementia for people with mild hearing loss is almost double that of a person with normal hearing, while the risk for people with a severe hearing loss is almost five times higher.

But it's not just older people who are affected.

Some recent studies have found that this increased risk of cognitive decline can also affect people who develop hearing loss in mid-life, before the age of 50.

So, given this link between hearing loss and cognition, it's important to investigate whether treatment of hearing loss with hearing aids could delay the onset of cognitive decline.

Our new research, published in the Journal of Clinical Medicine, has found that after 18 months of hearing aid use, 97.3 per cent of people in our study showed either a clinically significant improvement or stability in executive function.

Women, in particular, showed significant improvements in working memory as well as most other cognitive functions we assessed.

THE WIDER IMPACT OF HEARING LOSS

The World Health Organisation estimates that by 2030, some 82 million people worldwide will be living with dementia, increasing to 152 million by 2050, tripling the current number.

After 65 years of age, the risk of developing dementia doubles every five years, and 25 to 35 per cent of people aged over 85 years are affected.

Sadly, with an aging global population, the number of people affected by dementia is growing rapidly.

The mechanisms underlying the link between hearing loss and cognitive decline are still unknown and are likely to be multiple.

These may include neurodegeneration as part of the aging process, increased listening demands as a result of hearing loss that affect cognition, sensory deprivation, social isolation, loneliness and a lack of stimulation, associated depression which is a known risk factor for dementia, and a decrease in brain volume found in people with hearing loss.

Although hearing aids and cochlear implants are successful treatments for hearing loss, there is currently no successful treatment for cognitive decline.

But we do know hearing aid use can significantly reduce communication difficulties, loneliness, depression, and improve quality of life.

However, the research to date on the effects of hearing aids on cognition in older adults has significant limitations that make the findings difficult to interpret and leaves us with many unanswered questions.

THE CASE FOR HEARING AIDS

Our study into the effect of hearing aid use is a collaboration between the Department of Audiology and Speech Pathology, hearing care company Sonova AG, the Department of Economics and neuroscience technology company, Cogstate Ltd.

We work with people aged 60 and over with hearing loss who want to try wearing hearing aids for the first time – something they flagged at a visit to the University of Melbourne Audiology Clinic.

Before a hearing aid is fitted, their cognition is assessed. At 18-month intervals, it's tested again using card games played on a computer.

Other factors likely to influence cognition are also looked at including; social participation, genetic risk, loneliness, quality of life, mood, diet and physical activity.

Our initial results suggest that instead of declining, cognitive function in older adults with hearing loss who use hearing aids can not only remain stable, but can even improve significantly over time.

More frequent use of hearing aids is associated with greater improvements in cognitive function.

It seems possible, based on these results, that the treatment of hearing loss with hearing aids may delay cognitive decline.

In fact, hearing aid use could be a very safe and economical way to preserve cognitive function and improve quality of life for longer for older adults.

But despite the effectiveness of hearing aids as a treatment of hearing loss, it's estimated that up to 76 per cent of people who need hearing aids do not have them.

Of the very small number of people who do own hearing aids, a recent report showed that 24 per cent do not use them. The results of this study may encourage a greater number of people to use hearing aids in the future.

So, if you or someone you know struggles with hearing, go and have a hearing test. Getting a hearing aid could help keep your brain sharper for longer.

This study is continuing to recruit participants and will follow cognition over a longer period of time with larger numbers. If you're interested in taking part, please get in touch with the University of Melbourne Audiology Clinic – contact details are on their website.

This research was funded by Swiss company, Sonova AG. Sonova specialises in hearing care solutions and is one of the leading providers worldwide. Two of the paper authors, Ulrike Lemke and Stefan Launer, are affiliated with Sonova AG as employees. Participants were people who had been assessed as needing hearing aids and had decided to trial using them for the first time. Participants were fitted with the hearing aid of their choosing; they didn't have to be Sonova branded (though some did choose their products).