This is a plain English summary of an original research article. The views expressed are those of the author(s) and reviewer(s) at the time of publication.
A comprehensive review of research explored the link between adult-onset hearing loss, dementia, and problems with thinking and memory (cognitive impairment). Researchers found that:
- hearing loss was linked to an increased risk of mild to severe cognitive problems, including mild cognitive impairment and Alzheimer’s disease
- hearing loss was not linked to an increased risk of vascular dementia
- the greater the hearing loss, the higher the risk of dementia.
The findings support suggestions that addressing hearing loss might reduce the risk of some types of dementia.
More information about hearing loss can be found on the NHS website.
The issue: how harmful is hearing loss?
The Royal National Institute for Deaf People estimates that 18 million people in the UK have hearing loss in one or both ears. Some experts describe hearing loss as a modifiable risk factor for dementia, but previous findings are mixed. A 2022 systematic review found that people with hearing loss who use hearing aids or cochlear implants have a reduced risk of developing dementia. Similarly, a large randomised controlled trial found that hearing aids reduced the risk of cognitive decline by 48% in 70 – 84 year olds with untreated hearing loss (including people with low cognitive scores). However, hearing aids did not reduce dementia risk in those at low risk.
The current review pulled together previous research on hearing loss and dementia. Researchers assessed the link between hearing loss on dementia subtypes.
What’s new?
Researchers analysed 50 studies from the US, East Asia, Europe and Australia in a total of 1.5 million people. All studies explored the link between adult-onset hearing loss and cognitive outcomes, but outcomes were described in different ways (dementia for example, rather than Alzheimer’s disease).
The review considered the severity and type of cognitive impairment along with the degree of hearing loss; and looked at the impact of age and length of follow-up (at least 2 years for all participants). In half the studies, participants either self-reported hearing loss or had a history of hearing loss; in the remainder, they were assessed at the start of the study.
Those with hearing loss at the beginning of each study were compared to those with no hearing loss. Over the course of a study, people with hearing loss had:
- an increased risk of dementia (35% increase in 30 studies) and Alzheimer’s disease (56% increase in 4 studies)
- an increased risk of mild cognitive impairment (29% in 3 studies)
- an increased risk of unspecified cognitive decline (also 29% increase in 9 studies)
- no link between vascular dementia and hearing loss (in 3 studies).
The research suggested that:
- both mild and moderate to severe hearing loss were associated with increased dementia risk (7 studies for each finding)
- the greater the hearing loss, the greater the risk of cognitive decline (every 10 decibel decrease in hearing was associated with 16% increase in dementia risk; 2 studies)
- the link between hearing loss and dementia did not vary according to age at the start of the study (35 studies), or length of follow-up (37 studies).
Why is this important?
The findings support the suggestion that adult-onset hearing loss might be a cause of dementia. Results were consistent across studies, despite differences in the people included, and the type of cognitive impairment they looked at.
Adult-onset hearing loss can be treated, most often with hearing aids. Following on from this study, the researchers went on to explore the impact of wearing hearing aids on mild cognitive impairment.
What’s next?
The team has since included hearing loss as a risk factor for dementia in another NIHR-funded programme. The researchers developed an app (ENHANCE) which, with coaching support, aims to encourage people to adopt healthier lifestyles and reduce their risk of dementia. It targets hearing loss along with other risk factors such as high blood pressure, diabetes, physical inactivity and low mood. The app includes cognitive games to keep the mind active, educational health-related videos to encourage healthy behaviour, and tools for tracking health behaviours.
You may be interested to read
This is a summary of: Yu R-C, and others. Adult-onset hearing loss and incident cognitive impairment and dementia - A systematic review and meta-analysis of cohort studies. Ageing Research Reviews 2024; 98: 102346.
Evidence about dementia prevention and care: Dementia prevention, intervention, and care: 2024 report of the Lancet standing Commission. The Lancet Commissions 2024; 404: 572 – 628.
The experiences of people with cognitive impairment using hearing aids. Gregory, Sarah, and others. Experiences of hearing aid use among patients with mild cognitive impairment and Alzheimer’s disease dementia: a qualitative study. SAGE Open Medicine 2020; 8: 205031212090457.
An NIHR Evidence summary: How to identify dementia in people with hearing loss.
An article about hearing loss and dementia. Munro K J, Dawes P. Commentary: dementia, hearing loss, and the danger of professional rabbit holes. ENT & Audiology News September 2024.
Funding: This study was supported by the NIHR Programme Grants for Applied Research, the University College London Hospitals Biomedical Research Centre and Alzheimer's Research UK.
Conflicts of Interest: No relevant conflicts were declared. Full disclosures are available on the original paper.
Disclaimer: Summaries on NIHR Evidence are not a substitute for professional medical advice. They provide information about research which is funded or supported by the NIHR. Please note that the views expressed are those of the author(s) and reviewer(s) at the time of publication. They do not necessarily reflect the views of the NHS, the NIHR or the Department of Health and Social Care.
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