Adults suffering hearing loss could cut their risk of developing dementia by wearing a hearing aid, a new decade-long study suggests.
An international team of scientists compared outcomes by tracking 437,704 people with varying degrees of hearing impairment, whose data is stored in the UK biobank, a large-scale biomedical database and research resource containing in-depth genetic and health information from 500,000 British contributors.
The average age of participants when the study began was 56, with a mean follow-up time of 12 years.
The analysis published in The Lancet Public Health journal reveals those who did not use a hearing aid had a 42% higher risk of developing all-cause dementia within 12 years compared to those who chose to use a hearing device.
The research carried out by scientists from the UK, Japan, the US, China, Pakistan and Australia, indicates that tackling hearing loss at an early stage could be one of the easiest and most cost-effective ways of reducing the risk of dementia, currently amongst the biggest global health threats facing older adults. An estimated 153 million people are expected to be living with it by 2050.
Corresponding study author, Professor Dongshan Zhu of Shandong University in Jinan in Eastern China, said: “The evidence is building that hearing loss may be the most impactful modifiable risk factor for dementia in mid-life, but the effectiveness of hearing aid use on reducing the risk of dementia in the real world has remained unclear.
“Our study provides the best evidence to date to suggest that hearing aids could be a minimally invasive, cost-effective treatment to mitigate the potential impact of hearing loss on dementia.”
The latest findings come after the Lancet Commission on dementia prevention, intervention, and care, published in 2020, suggested that hearing loss may be linked to around 8% of worldwide dementia cases.
Around three-quarters of the participants in this latest study (325,882) had no hearing loss, and the remaining one-quarter (111,822) had some level of hearing impairment. Among those with hearing loss, 11.7% (13,092) used hearing aids.
Participants – none of whom had dementia at the start of the study – had self-reported if they suffered with hearing loss and used a hearing aid. Dementia diagnosis were gathered using National Health Service hospital records and death registrations.
After controlling for other factors, the study found a 1.7% risk of dementia in people with hearing loss who weren’t using any hearing devices. This compared to 1.2% among those with normal hearing or who were experiencing hearing loss but using an aid.
Professor Dongshan Zhu said: “Close to four-fifths of people experiencing hearing loss do not use hearing aids in the UK. Hearing loss may begin early in one’s 40s, and there is evidence that gradual cognitive decline before a dementia diagnosis can last 20 to 25 years.
“Our findings highlight the urgent need for the early introduction of hearing aids when someone starts to experience hearing impairment.
“A group effort from across society is necessary, including raising awareness of hearing loss and the potential links with dementia, increasing accessibility to hearing aids by reducing cost, and more support for primary care workers to screen for hearing impairment, raise awareness, and deliver treatment such as fitting hearing aids.”
The researchers also analysed how other factors, including loneliness, social isolation, and depressive symptoms, might impact the association between hearing loss and dementia.
The study suggests that less than 8% of the association between hearing aid use and decreased dementia risk could be removed by improving psychosocial problems.
The authors acknowledge that further research is needed to understand if there is a causal relationship between hearing loss and dementia. But they said their work suggests that hearing aids appear to have a direct protective role as opposed to simply lessening problems.
Other academics have urged caution following the publication of the research, however. Tim Griffiths, professor of Cognitive Neurology at Newcastle University, said: “The numbers are impressive and have allowed authors to assess multiple factors that might affect dementia risk apart from hearing loss.
“But this observational study needs to be interpreted with caution. The best quality data on the relationship between hearing loss and dementia were the studies included in a model developed by the Lancet Commission based on hearing tests (audiograms) and follow up of the patients to see if they developed dementia.
“The UK Biobank data does not include hearing tests: the hearing data is based on self-report which is not reliable.”
He added that hearing aid results were difficult to interpret for two reasons, the first being people with such devices often tend not to use them, which would work against the effect of their use shown in the study. Secondly, he said it is difficult to be certain if the association of not using hearing apparatus reflects dementia causing lower hearing aid use as opposed to the reverse.
He concluded: “So, the suggested effect is interesting but what we really need are prospective studies of hearing aid use that measure deafness, like the Lancet Commission studies, and carefully evaluate device use and incident dementia.”
Professor Griffiths said a large multisite US study funded by NIH, is currently doing that.
Robert Howard, professor of Old Age Psychiatry at University College London, said: “This is a large and well-conducted study, but we should always remember that association is not the same as causation.
“As the authors acknowledge, dementia may have a prodrome of more than 20 years, during which subtle neuropsychological changes affect motivation and behaviour.
“Anyone who has observed an older relative without dementia, as they use, or fail to use, their hearing aid, will understand just how important any subtle cognitive or motivational impairment would be in this.
“ I’m sceptical that use of hearing aids can be considered to prevent dementia. It seems more plausible to me that the association reflects that individuals on their way to developing dementia struggle to take up or use hearing aids.
“But hearing aids are important in reducing isolation and increasing quality of life, so we should encourage their use anyway.”
