Hearing aids could mitigate cognitive decline in older adults, but only in those who are particularly at risk of developing dementia.
Researchers have long speculated that hearing loss may raise the risk of dementia among older people, possibly by making them more socially isolated or by directly affecting regions of the brain that are involved in memory.
However, this was largely based on observational research that suggested a correlation between hearing loss and dementia, rather than work showing that the former causes the latter. It could be that people with dementia are less able to arrange hearing check-ups or remember to wear hearing aids.
Now, Frank Lin at Johns Hopkins University in Maryland and his colleagues have conducted a randomised control trial that directly compared the effects of wearing and not wearing a hearing aid on cognitive decline.
Out of 977 US adults aged between 70 and 84 with similar levels of hearing loss, around half were given hearing aids to wear daily, while the rest just received general health advice. None of the participants showed signs of significant cognitive impairment at the start of the study.
Three years later, there were no differences between the two groups when tested on their logic skills, word fluency, memory and decision making.
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The lack of a difference may be because 739 of the participants were volunteers who were already in generally good health and signed up to the trial after seeing it advertised. “If you use adverts to find people, it tends to be the people with more initiative and resources who take part, and they’re the ones who are already less vulnerable to cognitive decline,” says Gill Livingston at University College London.
The remaining 238 people were asked to take part after already being enrolled in a trial investigating the causes of atherosclerosis, thickening or hardening of the arteries due to plaque build-up. All of these participants had various heart-related risk factors, putting them in worse health than the other 739 volunteers.
These participants also tended to be older women who lived alone, had a lower income and had a less educated background, and they also had higher rates of diabetes and blood pressure – all of which have been linked to dementia.
Within this group, 120 of the participants wore hearing aids and 118 only received the health advice. When the researchers focused on these individuals, they found that those who wore a hearing aid experienced 48 per cent less cognitive decline over the three years, when assessed via the same tests.
“This is interesting because it gives us a clearer idea of the population who we should intervene in,” says Livingston. “You don’t intervene in everyone, you intervene in the people where you might make a difference, at least in the short term.”
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If the results are confirmed with further research, hearing aids may be a relatively simple, inexpensive way of tackling rising dementia rates. “Having a hearing aid is not like an intravenous injection,” says Livingston. “It doesn’t have either the cost or the likely side effects.”
Julia Sarant at the University of Melbourne, Australia, says that seeing a result like this in a randomised controlled trial could raise awareness of the importance of addressing hearing impairments.
“That evidence will hopefully spur people to use hearing aids,” she says. “It’s well known that, on average, most people wait seven to 10 years to seek help with their hearing and around 80 per cent of people who could benefit don’t use them.”
Journal reference:
The Lancet DOI: doi.org/10.1016/S0140-6736(23)01406-X