A recent study by Chinese scientists has provided the best evidence yet to suggest hearing aids could mitigate the potential impact of hearing loss on dementia, the decades-long research indicating that tackling hearing loss early could help reduce the global burden of the disease.
Dementia is one of the world’s biggest health threats. The number of people living with the condition worldwide is forecast to nearly triple to 153m by 2050, and experts have said it presents a major and rapidly growing threat to future health and social care systems in every community, country and continent.
People with hearing loss who don’t wear a hearing aid may have a higher risk of dementia than people without hearing loss, research suggests. But this latest study found that using a hearing aid could reduce this risk to the same level as people without hearing loss.
The findings were published in The Lancet, following The Lancet Commission on dementia prevention, intervention and care published in 2020, which suggested hearing loss could be linked to about 8% of worldwide dementia cases.
“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, until now” said Professor Dongshan Zhu of Shandong University, China.
The researchers looked at data from 437 704 people taking part in the UK Biobank study. The average age was 56, and the average follow-up time was 12 years.
They found that compared with people with normal hearing, those with hearing loss who were not using hearing aids had a 42% higher risk of all-cause dementia. There was no increased risk in people who used hearing aids.
This is approximately equivalent to a 1.7% risk of dementia in people with hearing loss who are not using hearing aids, compared with 1.2% among those without hearing loss or who are experiencing hearing loss but using the devices, the researchers said.
“Close to four-fifths of people experiencing hearing loss do not use hearing aids in the UK,” said Zhu. “Hearing loss may begin early in the 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.”
Robert Howard, professor of old age psychiatry at University College London, who was not involved in the study, said: “This is a well-conducted study, but we should always remember that association is not the same as causation.”
“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.”
Study details
Association between hearing aid use and all-cause and cause-specific dementia: an analysis of the UK Biobank cohort
Fan Jiang, Shiva Raj Mishra, Nipun Shrestha, Akihiko Ozaki, Salim Virani, Tess Bright, et al.
Published in The Lancet on 13 April 2023
Summary
Background
Dementia and hearing loss are both highly prevalent conditions among older adults. We aimed to examine the association between hearing aid use and risk of all-cause and cause-specific dementia among middle-aged and older-aged adults, and to explore the roles of mediators and moderators in their association.
Methods
We used data from the UK Biobank, a population-based cohort study, which recruited adults aged 40–69 years between 2006 and 2010 across 22 centres in England, Scotland, and Wales. We used Cox proportional hazards models to estimate hazard ratios (HRs) and 95% CIs between self-reported hearing aid use status (hearing loss with or without hearing aids) at baseline and risk of dementia (all-cause dementia, Alzheimer's disease, vascular dementia, and non-Alzheimer's disease non-vascular dementia). Dementia diagnoses were ascertained using hospital records and death-register data. We also analysed the roles of mediators (self-reported social isolation, loneliness, and mood) and moderators (self-reported education and income, smoking, morbidity, and measured APOE allele status).
Findings
After the exclusion of people who did not answer the question on hearing difficulties (n=25 081 [5·0%]) and those with dementia at baseline visit (n=283 [0·1%]), we included 437 704 people in the analyses. Compared with participants without hearing loss, people with hearing loss without hearing aids had an increased risk of all-cause dementia (HR 1·42 [95% CI 1·29–1·56]); we found no increased risk in people with hearing loss with hearing aids (1·04 [0·98–1·10]). The positive association of hearing aid use was observed in all-cause dementia and cause-specific dementia subtypes (Alzheimer's disease, vascular dementia, and non-Alzheimer's disease non-vascular dementia). The attributable risk proportion of dementia for hearing loss was estimated to be 29·6%. Of the total association between hearing aid use and all-cause dementia, 1·5% was mediated by reducing social isolation, 2·3% by reducing loneliness, and 7·1% by reducing depressed mood.
Interpretation
In people with hearing loss, hearing aid use is associated with a risk of dementia of a similar level to that of people without hearing loss. With the postulation that up to 8% of dementia cases could be prevented with proper hearing loss management, our findings highlight the urgent need to take measures to address hearing loss to improve cognitive decline.
The Guardian article – Hearing aids could help cut the risk of dementia, study finds (Open access)
See more from MedicalBrief archives:
Four in 10 dementia cases could be prevented or delayed — Lancet Commission
Hearing aids improve cognitive function — Australian study
Hearing aids linked to reduced risk of mental decline and falls but few get them
Losing hearing in middle age may increase dementia risk