Hearing impairment in older adults was strongly and independently associated with the likelihood of having dementia (memory loss), according to a case-control study published in the Journal of the American Medical Association nearly 22 years ago.
But due to various reasons, this study received little attention until recently, and today scientists have confirmed the association between untreated hearing loss and dementia and Alzheimer’s disease.
What is the evidence for Hearing loss and Dementia / Alzheimer’s disease
Growing evidence has suggested that hearing impairment is independently associated with a 30–40% rate of accelerated cognitive decline and with a substantially increased risk of incident all-cause dementia.
Compared to individuals with normal hearing, people with a mild, moderate, and severe hearing impairment, respectively, had a 2-, 3-, and 5-fold increased risk of incident all-cause dementia over >10 years of follow-up.
Neuroimaging studies have also shown independent associations between hearing impairment and reduced cortical volumes in the auditory cortex and accelerated rates of lateral temporal lobe and whole brain atrophy.
How hearing loss causes dementia / Alzheimer’s disease?
Age-related hearing loss is a condition that will affect nearly every person in society.
The prevalence of hearing impairment doubles with each age decade, such that nearly two-thirds of adults 70 years of age and older have a meaningful hearing loss that affects daily communication.
Studies have shown that greater cognitive resources are required for processing the weak auditory signals generated, leading to the detriment of other cognitive processes such as working memory.
Reduced stimulation from the impaired cochlea (organ of hearing) may precipitate changes in cortical reorganization and brain morphometry, which may act as a “secondary insult” to the brain in patients with other underlying clinical conditions.
In a recent study published in the journal Neuron, a team of researchers from New Castle University proposed a new theory regarding the relationship between hearing loss and dementia or Alzheimer’s disease. They postulated that memory centres deep in the temporal lobe of the brain, associated with long-term memory for places and events, are also involved in the short-term storage and manipulation of auditory information. Researchers propose that altered activity in the memory system caused by hearing loss and the Alzheimer’s disease process trigger each other.
Will a hearing aid help in prevention of Dementia / Alzheimer’s disease?
Some experts believe that interventions, like professionally fitted hearing aids, could potentially delay or prevent dementia.
There is some emerging evidence in a recent meta-analysis and systematic review (Yeo et al, 2022); researchers found that hearing aid users had lower hazards of cognitive decline relative to non-users as well as a three percent improvement in cognitive test scores after the use of hearing aids.
While it is possible that hearing rehabilitative therapies and devices could plausibly lessen cognitive load, provide increased auditory stimulation, and promote social engagement, there has been no research that has investigated whether such therapies could actually reduce the risk of cognitive decline and dementia.
Results from observational epidemiologic studies have demonstrated trends for a protective effect of hearing aid use, but such results remain difficult to interpret.
Research in these areas is ongoing. Though the early studies are still inconclusive, it is proven that people with hearing difficulty who use hearing aids are more likely to have a strong support network of family and friends, feel engaged in life, and meet up with friends to socialize. Maintaining strong social connections and keeping mentally active as we age might lower the risk of cognitive decline and Alzheimer’s disease.
Any senior experiencing hearing loss should make a point to seek out treatments for it.
References
- Lin FR, Albert M. Hearing loss and dementia–who is listening?.
- Hung SC, Liao KF, Muo CH, Lai SW, Chang CW, Hung HC. Hearing loss is associated with risk of Alzheimer’s disease: a case-control study in older people. Journal of epidemiology. 2015 Aug 5;25(8):517-21.
- Uhlmann RF, Larson EB, Rees TS, Koepsell TD, Duckert LG. Relationship of hearing impairment to dementia and cognitive dysfunction in older adults. JAMA. 1989;261(13):1916–1919.
- Timothy D. Griffiths, Meher Lad, Sukhbinder Kumar, Emma Holmes, Bob McMurray, Eleanor A. Maguire, Alexander J. Billig, William Sedley. How Can Hearing Loss Cause Dementia? Neuron, 2020
- Yeo BSY, Song HJJM, Toh EMS, et al. (2022) Association of hearing aids and cochlear implants with cognitive decline and dementia: a systematic review and meta-analysis. JAMA Neurol. In press.