The Link Between Hearing Loss And Alzheimers Disease
Adults with hearing loss have a higher risk for Alzheimers and other cognitive disorders
The risk of dementia increases for those with a hearing loss greater than 25 dB.
of the risk of dementia was associated with hearing loss for study participants over the age of
Individuals with moderate to severe hearing loss are up to 5 times as likely to develop dementia.
According to several major studies, older adults with hearing lossespecially men are more likely to develop Alzheimer’s disease and dementia, compared to those with normal hearing. Men with hearing loss were 69 percent more likely to develop dementia than those with no hearing impairment.
The risk escalates as a person’s hearing loss worsens. Those with mild hearing impairment are nearly twice as likely to develop dementia compared to those with normal hearing. The risk increases three-fold for those with moderate hearing loss, and five-fold for those with severe impairment.
Introduction: Scope And Nature Of The Problem
Hearing impairment in later life is a major clinical issue and a leading association of cognitive decline , presenting significant potential opportunities for dementia diagnosis, treatment and prevention . But how are hearing impairment and dementia related? Hearing loss of any cause tends to limit social engagement and quality of life , amplifies the effects of cognitive impairment and may confound or delay diagnosis of dementia . Conversely, diagnosis of hearing loss and compliance with hearing aids are hindered by cognitive impairment . There may, however, be a more fundamental pathophysiological basis for the association: hearing is a complex cognitive function that, alongside other cognitive functions, is directly vulnerable to the pathophysiological processes that cause dementia .
Evidence that neurodegenerative pathologies target the auditory brain and produce central hearing deficits disproportionate to any peripheral hearing loss was first produced some time ago . More recently, a diverse array of central auditory deficits has been described in these diseases , ranging widely beyond deafness to encompass altered auditory perception, understanding and behavioural responses, with far-reaching consequences for hearing function in daily life. To date, however, the role of the auditory brain in linking hearing impairment to cognitive decline has been largely overlooked.
Can Hearing Aids Help Prevent Dementia
Hearing loss is the third most common health condition affecting older adults, occurring in one-third of people over age 65 and in two-thirds of those over age 70 . It has been identified as one of the top potentially modifiable risk factors for dementia by the Lancet Commission on Dementia Prevention, Intervention, and Care . Although studies suggest that restoring auditory input may help protect cognitive function and improve quality of life , hearing aids are expensive. There are several factors to consider when determining how to cope with hearing loss.
WHAT THE EVIDENCE SAYS
Mild hearing loss is associated with two-fold greater risk for dementia, while severe hearing loss is associated with 5 times greater risk over 10 years . Several longitudinal studies have found that the rate of cognitive decline is accelerated in dementia patients with hearing loss . Participants with hearing loss experienced rates of cognitive decline that were 30-50% faster than those with normal hearing .
A recent study following over 1,000 participants in the Rancho Bernardo Study of Healthy Aging for up to 24 years found that hearing impairment was associated with faster age-related declines in global and executive cognitive function . The cognitive decline associated with mild hearing loss was reduced in individuals who attained higher education, but education could not protect against declines associated with moderate to severe hearing loss.
Hearing Impairment: Cause Canary Or Corollary Of Dementia
The complex pathophysiological relations between hearing impairment and dementia remain to be fully defined. Impoverished sensory fidelity due to peripheral hearing loss or disturbed subcortical auditory trafficking will potentially have effects both on auditory cognition and more general cognitive functions such as attention, executive processing and perceptual learning , leading to vicious cycling. Hearing loss might therefore produce both syndromic and generic cognitive signatures. The balance of these is likely to depend on stimulus and task demands as well as the particular neurodegenerative process. Emerging epidemiological evidence suggests that hearing impairment may potentiate neurodegeneration, perhaps via an interaction of aberrant auditory activity with culprit proteinopathies in vulnerable neural circuits . Indeed, hearing impairment might constitute a facilitating cause of neurodegenerative disease evolution, an early warning canary for impending cognitive disaster or an accompaniment of established dementia: these non-exclusive mechanisms would have mutually reinforcing consequences for auditory brain function.
When To Get Your Hearing Checked
Some people ignore signs of hearing loss, or chalk them up to aging and just live with it. But hearing loss can affect your life in many ways, so if you suspect youre at risk, talk to your doctor.
Ask for an audiology evaluation to determine how severe the hearing loss is, Dr. Factora says. If you do have hearing loss and your physician offers a solution like hearing aids, try them out, he says.
If you wait too long and develop memory problems, it will be more difficult for you to learn how to use these devices. Its best to get used to them while the mind is still sharp so you can improve your quality of life.
While you cant prevent cognitive issues from developing as you age, you can slow the onset of dementia through lifestyle interventions, Dr. Factora says.
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General Comments On Mechanisms
None of the four mechanisms above can be ruled out. In our view, common pathology is a weak candidate, especially in the majority of incident dementia cases that are due to AD. The idea of a predisposition to dementia due to impoverished environment is supported by animal data that suggest precise neuronal and anatomical bases and human data that demonstrate structural changes due to hearing loss in cortex that is vulnerable to early AD. Mechanisms 3 and 4 can both be based on the increased use of general cognitive resources, with a substrate including the MTL, under difficult listening conditions. Mechanism 3 is based on increased activity alone, and is also a weak candidate basis for long-term dementia pathology. We favor mechanism 4, in which increased activity interacts with pathology in the MTL. The argument for this is based on auditory cognitive mechanisms that are relevant to difficult listening in the MTL and studies of the distribution of AD pathology. However, there is no direct evidence for the specific interaction between the two in the MTL that we propose. Finally, we should point out that the possible mechanisms are not exclusive. For example, impoverished auditory experience could cause structural changes in the MTL and a decreased cognitive reserve to protect against dementia , after which there is a specific interaction between activity changes in the MTL and AD pathology .
Need A Refresher On The Difference Between Correlation And Causation
Correlation means two things are merely associated with each other or have some relationship to each other. Causation means that one thing causes another. Here is an example to help clarify the difference:
On days where there are is a spike in the sale of sunscreen, there is also a spike in incidents of drowning. Does this mean buying sunscreen causes people to drown?? Probably not. Most likely, the common denominator is hot summer days. On hot summer days, more people go out to buy sunscreen and more people decide to go swimming. And the more people who swim, the higher the probability that someone will drown. Just because more people buy sunscreen on the same days that more people drown doesnt mean buying sunscreen causes drowning!
Okay so now that weve clarified the difference between correlation and causation, we can get back to talking about what you really came here to read: the relationship between hearing loss and dementia.
Basically, scientists have been able to prove that there is a correlative relationship between hearing loss and cognitive impairment. But they havent been able to prove that hearing loss causes cognitive impairment.
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Mechanism : Increased Cognitive Resources Needed For Listening
A third mechanism is based on the idea that people with hearing impairment use greater cognitive resources for listening, making these resources unavailable for other aspects of higher cognition when they are âoccupiedâ during listening. âResourcesâ refers here to the means for cognitive tasks such as attention , working memory , or language processing . There is debate about how cognitive resources are allocated, and the corresponding neural bases. With respect to working memory, for example, there is a question about the extent to which resources may be specifically allocated to objects or represent a distributed resource . Further debate concerns the extent to which working memory resources reflect neuronal or synaptic mechanisms, or both . What is important here, however, is that there is a fixed capacity for many general cognitive operations. These resources may be absorbed when listening becomes challenging, reducing their availability for other aspects of cognition.
Mechanisms 2 and 3 may at first appear at odds: in mechanism 2, the problem is the decreased stimulation of auditory cognitive networks, while in mechanism 3, there is increased stimulation. The critical difference is that mechanism 2 leads to changes in neuronal mechanisms and brain structure before the onset of dementia, causing an increased risk of subsequent dementia, while mechanism 3 is based on changes in brain activity during dementia that may explain the cognitive deficits.
Coping With Dementia And Hearing Loss
Living with both conditions is more difficult than living with either on its own. Both dementia and hearing loss can have an impact on how someone copes day to day for example, making it harder to communicate. They can also both lead to increased social isolation, loss of independence, and problems with everyday activities, and as a result make the persons dementia seem worse.
However, there are things that can help.
- Having regular hearing checks and making the most of the hearing the person does have for example, by using hearing aids.
- Improving the environment, for example by reducing background noise and distractions and making sure the area is well lit.
- Finding out the persons preferred way of communicating for example, lip reading.
- Using gestures and expressions, and letting people see your face when communicating.
- Using visual clues and prompts.
If the person needs hearing aids, these are available free on the NHS, or you can buy one privately. Many older people struggle to use a hearing aid correctly all the time. It can take time for a person to get used to a hearing aid, and it will take a person with dementia longer. It is also important to consider whether a hearing aid is the best option an audiologist should be able to advise.
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New Dementia Theory Grapples With Hearing Loss
A new theory suggests a possible link between Alzheimers disease, an important memory centre in the brain, and hearing loss.
Reasearchers with Newcastle University in the U.K. in Neuron, a neuroscience journal, in early September, looking at existing research into hearing and Alzheimers. One study suggested an estimated nine per cent of cases of dementia can be attributed to hearing loss.
Studying findings from a variety of studies of dementia in humans and animals, the researchers focused on the temporal lobe , the part of the brain crucial to memory and also plays a role in processing sound.
Hearing Loss And Dementia: A Meta
- 1Jiangsu Provincial Key Medical Discipline , Department of Otolaryngology Head and Neck Surgery, Affiliated Drum Tower Hospital of Nanjing University Medical School, Nanjing, China
- 2Department of Neurology, The Fourth Affiliated Hospital of Nanjing Medical University, Nanjing, China
Background: Consensus is lacking with regard to whether hearing loss is an independent risk factor for dementia. We therefore conducted a meta-analysis to clarify the relationship of hearing loss and dementia.
Methods: Prospective cohort studies investigating the association between hearing loss and the incidence of dementia in a community-derived population were included by searching electronic databases that included PubMed, Embase, and Cochrane’s Library. A random-effects model was adopted to combine the results.
Results: Fourteen cohorts including 726,900 participants were analyzed. It was shown that hearing loss was independently associated with dementia . Sensitivity analysis sequentially excluding any of the individual studies included showed similar results. Subgroup analysis according to the diagnostic methods for hearing loss, validation strategy for dementia, follow-up duration, and adjustment of apolipoprotein E genotype also showed consistent results . Meta-analysis with five studies showed that hearing loss was also connected to higher risk of Alzheimer’s disease .
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Can Hearing Loss Cause Dementia And Cognitive Decline
The older we get, the more our bodies begin to fail after all, the human body was never meant to last forever. When one system begins to decline, however, it can affect the functioning of another, and the result is not always positive. This is especially true when it comes to our hearing.
Hearing Loss and Cognitive Decline
Hearing loss is often associated with old age, but research in recent years has also begun to connect it with other conditions, such as dementia and cognitive decline. In fact, studies cited by the National Center for Biotechnology Information have shown that individuals with hearing impairment have a higher risk of developing dementia than those who have no impairment. Other studies results have indicated that hearing loss may accelerate the onset and progression of cognitive decline that often comes simply as a result of aging.
How are hearing loss and dementia connected?
Researchers continue to try to find answers to this question, but here are four prominent theories that may explain the connection, at least in part:
Hearing loss treatment
Association Between Hearing Loss And Incident Dementia
Twelve prospective cohort studies were analyzed in the meta-analysis of hearing loss and risk of all-cause dementia. Since one study provided separate data according to the number of ears affected , two studies according to the severity of hearing loss , and the others according to the age of the participants , these datasets were independently examined. As a result, 17 datasets were available for the outcome of all-cause dementia . Pooled results showed that hearing loss elevated the risk of subsequent dementia . Sensitivity analysis also showed consistent results . Subgroup analysis by the diagnostic methods for hearing loss, validation strategy for dementia, follow-up duration, and adjustment of APOE genotype also showed consistent results . Pooled analyses with five studies showed that loss was independently associated with a higher incidence of AD .
Forest plots for the meta-analysis concerning the association between hearing loss and the subsequent incidence of Alzheimer’s disease .
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Telling The Difference Between Sight Loss Symptoms And Dementia
It is often hard to separate the signs of sight loss from those of dementia, and often one condition may mask the other.
Having difficulty with any of the following may suggest a person is having problems with their sight.
- coping with low light, bright light or both
- finding things
- locating food on their plate
- seeing well even with glasses on.
Some of these issues may be caused by the persons dementia. However, it is important to have the person’s sight tested as difficulties with their sight could be making their confusion worse.
Despite what many people think, it is possible for a person with dementia to have a sight test. The test can be adapted for people with dementia, if it is needed.
My Hearings Not That Bad
Hearing aid users wait, on average, 10 years before getting help for hearing loss. But during that time, communication with loved ones becomes more difficult, and isolation and health risks increase. Our findings emphasized just how important it is to be proactive in addressing any hearing declines over time,says Lin.
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Opportunities For Further Research
Because the onset of dementia remains so unpredictable, many patients and family members are unable to recognize the development of the condition until it has become more severe. Because hearing loss is now considered to be a potential early sign of dementia, it may help loved ones and medical professionals identify symptoms more quickly. Researchers are also considering the efficacy of utilizing hearing aids and other forms of hearing recovery as a preventative treatment for early stages of dementia.
Further research is needed to verify the exact relationship between hearing loss and dementia, but the recently uncovered correlation has already led to new insights surrounding the condition. If uncovered, hearing loss could become both a widely acknowledged risk factor for dementia, and a means of initiating early forms of preventative treatment.
Dementia And Hearing Loss
Many people with dementia will also be living with hearing loss. It is common for people to develop gradual hearing loss as they age. People with hearing loss are also more likely to develop dementia, although at present we dont know why this is. Living with both conditions can present challenges, but there are many things which can help people to live well with both hearing loss and dementia.
Someone may have acquired hearing loss which has developed during the persons lifetime . Other people may have been born deaf or became deaf at a young age and are considered to have profound deafness. They may consider themselves as Deaf , use British Sign Language as their first language and identify with the Deaf community.
In this section we look at acquired hearing loss the problems with telling the difference between signs of dementia and acquired hearing loss, and how to help someone who has both.