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Why Does Hearing Loss Cause Dementia

Introduction: Scope And Nature Of The Problem

Hearing loss and dementia

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.

Identification Of Hearing Loss

It is important that older people with dementia have regular hearing checks, particularly because the symptoms of hearing loss for example, not following a line of conversation can be mistaken for dementia. In the first instance, the GP should be contacted as they will be able to refer the person for a hearing check, where appropriate.

It can be more challenging to diagnose hearing loss for people with dementia. A person has dementia may well find it hard to understand instructions given during the diagnostic process or they may be unable to report the history of their hearing loss because of their memory problems.

It is possible to adapt testing procedures so that they meet the needs of people with dementia. This makes it vital that care providers communicate effectively, where appropriate, with health professionals to ensure that they are aware of long-term conditions, such as dementia, that may have implications for testing procedures.

Some audiology departments have specialists who are qualified to assess people with dementia. They will often use specialist diagnostic tests, which are easy to understand and take account of the communication and memory difficulties that can go along with dementia.

Hearing Loss Causes Brain Changes And Dementia

The fourth mechanism that the researchers propose relates to changes in the brains medial temporal lobe .

People with Alzheimers disease have abnormal accumulations of a protein called tau that collects inside neurons. These accumulations are called neurofibrillary tangles. People with Alzheimers disease also have excess beta-amyloid 42, a protein that clumps together to form plaques between neurons. These neuron changes appear earliest in the MTL, which is involved in auditory processing.

People with hearing loss also display changes in MTL neurons, suggesting a relationship between the two conditions. The researchers suggest that in people with hearing loss, limited auditory input leads to overactivity in the MTL, which may cause or contribute to neurofibrillary tangles and beta-amyloid plaques.

They also suggest a two-way relationship, meaning that hearing loss may exacerbate changes that lead to Alzheimers disease, while the disease may cause changes that worsen hearing loss.

The researchers conclude that more research is necessary to clarify the processes that connect hearing loss and dementia.

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The Presentation Of Age

Age-related hearing loss , also known as presbycusis, accounts for the largest percentage of hearing loss cases around the world and presents as a gradual decrease in hearing ability. The outer hair cells and other sensory cells in the cochlea are progressively damaged and unable to regenerate . The result is the impaired encoding of sound, decreased precision, and a distorted auditory signal sent to the brain. This form of hearing loss commonly leads to decreased detection of the higher frequency sounds of speech before lower frequency sounds. The result is reduced ability to hear high-frequency consonants , the parts of speech that provide crispness and clarity. In turn, many with ARHL do not necessarily report difficulty with volume of speech but instead indicate speech sounds muddled or garbled, especially when in the presence of background noise. For everyday function, this may lead to difficulty communicating or interacting with others depending on the listening environment. Those with ARHL may have difficulty hearing or understanding what others are saying in a crowded or noisy setting, such as a restaurant. They may also have difficulty hearing and understanding the television, on the phone, when someone speaks from another room or with their back turned.

Evaluating Hearing Loss As A Risk Factor For Dementia

What are the most frequent causes of hearing loss?

All of the studies indicated that hearing loss is independently associated with higher incidence of dementia. The majority of the studies quantified the relationship using standard deviations, hazard ratio, relative risk, or odds ratio.4, 13, 14, 15, 16, 17, 18, 20, 21, 22, 24, 26, 27 Four studies found a doseresponse relationship between the severity of hearing loss and an increased risk of cognitive decline.13, 18, 19, 23 One study found that for every 10 dB HL at baseline, there was a 1.27 increased risk for allcause dementia and 1.20 increased risk for developing AD.23 Another study found the dose response curve to be a 1.5 point score decrease in the DSST cognitive test for every 10 dB HL.19 A third study found that for every 1 point increase in the hearing impairment scale, the likelihood of developing dementia five years later increased by 22%.18 Another study found the dose response to be an increased hazard ratio of 1.14 for every 10 dB HL.13 Two of the studies also employed other measurement systems for example, a 25 dB hearing loss is the equivalent cognitive performance of an individual 6.8 years older ,3 or moderate to severe hearing loss resulted in worse scores on the MMSE .25 One study quantifying the relationship with a hazard ratio also found a 0.26 points per year faster decline on 3MSR when HL was present .15

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Study Design And Population

A population-based retrospective matched cohort study was conducted. Disease diagnosis followed the regulations of the International Classification of Diseases, Ninth Revision, Clinical Modification . ICD-9-CM code 388.2 was used to define SSHL. Medical records that matched with these codes were obtained from the NHIRD between 2000 and 2009 for further analysis. Patients diagnosed with SSHL between January 1, 2000, and December 31, 2009, for > 1year who had attended 2 outpatient visits or received any inpatient diagnosis were included as the SSHL group. Patients diagnosed before 2000, aged < 20years, or diagnosed with dementia before SSHL were excluded. A total of 3731 newly diagnosed patients with SSHL were included, and through propensity score matching at a 1:3 ratio according to age, sex, index year, comorbidities, and medications , the comparison group was constructed. For patients without SSHL or dementia, the index date was designated as 365days after the diagnosis date. At last, 3725 patients with SSHL and 11,175 without SSHL were selected. The study was approved by the Institutional Review Board of Kaohsiung Medical University Hospital -20,160,028). All methods were carried out in accordance with relevant guidelines and regulations. Because the patient identifiers were scrambled to the public for research purposes to protect confidentiality, the requirement for written or verbal consent from patients for data linkage study was waived.

Fig. 1

Major Dementias Have Diverse Auditory Phenotypes

The neurodegenerative diseases that cause canonical dementia syndromes have specific profiles of large-scale, cortico-subcortical network involvement, determined by the patterns of spread of pathogenic proteins . These pathologies have correspondingly diverse clinical phenotypes including prominent auditory cognitive deficits .

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Ways Hearing Loss May Lead To Dementia

  • The constant effort to hear may stress the brain to the point that less energy is given to functions such as memory and understanding.
  • Certain parts of the brain that affect hearing can shrink when they dont get enough stimulation.
  • Being hard of hearing often leads to social isolation, which is a risk factor for cognitive decline and depression another common risk associated with hearing loss.
  • On-going research points to a possible common physiological pathway, such as high blood pressure, that contributes to both hearing loss and dementia.

Colonial Center for Hearing

Were dedicated to helping you hear better. How does that sound?At Colonial Center for Hearing Audiology, we guarantee youll get the professional, expert service you deserve. Our mission is to provide you with state-of-the-art hearing aid solutions and warm, caring customer service. Our exclusive Extended Warranty Plan, our Outreach and Referral Programs, and the fact that we have one of the best magazine selections in town, are just a few of the great reasons why our clients keep coming back.

At Colonial Center for Hearing Audiology, we take pride in providing an outcomes-based practice. This means well give you as many follow-up visits as takes to make sure youre fully comfortable and satisfied with your good hearing solutions.

Dementia And Hearing Loss

The Link Between Hearing Loss and Dementia

Hearing loss can be a sudden or gradual change in how well you hear. People with hearing loss may notice difficulties with everyday conversations, especially in noise. Dementia is a general term for a group of symptoms that impact abilities to think, remember, and reason through activities of daily living. Understanding the symptoms of hearing loss and dementia, and the connection between them can be helpful in ensuring proper prevention, diagnosis, and treatment.

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Do Hearing Aids Reverse Cognitive Decline

Dr. Curhans research didnt get a clear answer to this question. Among volunteers with severe hearing loss, those who wore hearing aids had a slightly lower risk of subsequent subjective cognitive decline than those who didnt. But the effect was too small to be statistically significant.

Because they keep you connected withothers, hearing aids can help preventsocial isolation.

She would like to see hearing aids and cognitive decline get a hard look. There isnt much evidence over long periods of time and what we have isnt conclusive, she notes. Several studies have found no relation between hearing aid use and cognitive function decline, while others have been suggestive of a possible association, she told Healthy Hearing. This relation merits further study.

One recent and very large observational study did shed more light on this issue, finding that hearing aids appeared to delay the onset of cognitive impairment and dementia, along with depression and falls that cause injuries. However, it was not a randomized controlled trial, so the results could have been for other reasons .

As well, one large 2018 study analyzed results from more than 2,000 Americans age 50 and up who took word recall tests every two years for up to 18 years. Among those who acquired hearing aids along the way, the evidence suggested that the aids slowed the rate they lost memory of words.

His answer, Do they do it from the drawer?

More: Health benefits of hearing aids

What Do We Mean By Hearing Loss Or Dementia

While the terms hearing loss and dementia are common conditions within health care and for older adults, what we mean by them is rather complex. When we say hearing loss, we are really referring to two processes that simultaneously are working together to allow an individual to hear in a given environment and for communication what you might call peripheral hearing ability and speech-in-noise performance . Similarly, dementia can be considered along a continuum and is diagnosed via clinical expertise, case history, neurocognitive assessments, and laboratory studies or medical imaging if available. A dementia diagnosis may stem from multiple potential etiologies. While it seems pedantic, these distinctions are essential when we consider both the possibility of hearing loss causing dementia and/or cognitive decline and subsequently advises the direction and potential fruitfulness of our intervention efforts. Interested readers are referred to the reference list for articles with more comprehensive discussion of the points presented here.

Peripheral hearing loss: the ability to detect a sound or speech

A patient listens for the softest sounds they can hear during a hearing test.

Speech-in-noise performance: the ability to hear and understand in the presence of background noise

Self-Reported Hearing Loss: a persons perception of how they hear

Distinguishing between Dementia or Cognitive Decline

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Hearing Loss And Dementia: Nancys Story

It is essential to recognise and respond sensitively to hearing loss in people with dementia. If a person with dementia is unable to communicate problems they are having with their hearing, this is likely to cause distress. They may well be frustrated or aggressive, but unable to say why and these reactions then may be interpreted as being a result of the dementia.

Both identification and management of hearing loss are particularly important where a person has dementia. Without this, the dementia may appear worse or get worse. For example, if a person with dementia is having difficulty using their hearing aid say they dont remember to use it or dont recognise it as their hearing aid this is likely to make it harder for them to follow communication and may make them seem more confused and withdrawn.

Both hearing loss and dementia can cause social isolation. Where someone is experiencing both of these, this can be compounded. For example, the person may be unwilling to attend social functions or participate in activities because their problems with hearing and memory make social situations so much more uncomfortable.

Research Shows Many Causes Early Symptoms

Studies link hearing loss and dementia

Everything from genes and noise exposure to medications, head injuries and infections can play a role in hearing loss. Trouble detecting soft or high-pitched sounds is often the first sign that stereocilia the delicate hair cells that convert sound waves into electrical signals within the earhave been damaged. Soft sounds include phone conversations or background noise in settings such as restaurants. High-pitched sounds may include childrens voices. Ringing in the ears, called tinnitus, is another early signal of possible hearing loss.

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The Relationship Between Hearing Loss And Dementia

11/01/2018 | Patient Resources |

Alzheimers disease is something we should all be clued up on. As many as 1 in 10 Americans get it. Despite it being so common, Alzheimers is often spotted long after it emerges and is sometimes under-treated. Early symptoms can get dismissed as part of growing old. The good news is that when it is diagnosed early, treatment can slow the progression of the disease and prolong quality of life. However, thats only possible when you know what the early symptoms are, right? It also helps to know about the risk factors, which include hearing loss.

Hearing Loss And Dementia: Advice For Care Staff

On average, people who develop hearing loss wait ten years after they first notice symptoms before they seek help . This means that a person may have developed other long-term conditions such as dementia alongside their hearing loss. Their circumstances may have changed and may well lose the opportunity to get hearing aids.

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The Cocktail Party Effect

Most previous studies have focused on our ability to detect sounds, but a new area of research focuses on the cocktail party effect. This is the challenge people have focussing on a single speaker or conversation in a noisy environment. Alzheimers Research UK is working with the RNID and Prof Jason Warrens team at University College London to investigate whether this could be an early warning sign for dementia.

Impaired Social Interaction May Affect Brain Function

Hearing Loss Causes – 23 Different Reasons Why Hearing Loss Occurs!

People with hearing loss receive degraded auditory input from their environment. When socializing, they may miss out on verbal and emotional information, which is crucial in social interaction. The loss of this vital information may directly impair brain structure and function.

According to the authors, reduced social interactions are as much of a risk factor for dementia as smoking and inactivity.

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Why Hearing Loss Is Associated With Dementia

Damage to your ears and damage to your brain doesnt always start off related. But over time, something as simple as hearing loss can become a significant risk factor for cognitive decline, up to and including dementia. Which is not a super fun thought, right?

Because of the way it affects your brain, untreated hearing loss can often cascade into a series of other cognition or health-related issues. Preventing these related issues is just one of the reasons why seeking out treatment for your hearing loss is so important. And, in this case, knowing why hearing loss can cause dementia can help you diminish and control your overall risk.

What Can You Do

If you want try to lower your chances of hearing loss as you age, try to keep your heart healthy, protect your hearing from loud noises, and donât smoke.

âSmoking is a big risk factor for sensory loss — vision and hearing,â says Heather Whitson, MD, at Duke Health.

Even when they take precautions, some people are simply more likely to get hearing loss in older age. In those cases, can using hearing aids protect you from dementia?

âThatâs the billion-dollar question,â Lin says.

Lin is leading a 5-year clinical trial studying 850 people to see if hearing aids can cut dementia.

Even without the proof, Lin says thereâs no downside to using hearing aids. In fact, thereâs often a big upside to getting help for your hearing loss.

âWith a very simple intervention, we could make a big difference improving quality of life,â Lin said.

In a pilot study, people with dementia started wearing inexpensive, over-the-counter devices to boost their hearing. A month later, their caregivers reported improved communication, more laughter, and more storytelling.

âIf youâre an older adult with hearing loss, it would make sense to treat that hearing loss,â says Richard Gurgel, MD, of the University of Utah.

If you think your hearing has gotten worse with age, Gurgel recommends a hearing screening. The relatively quick, painless test can help you notice how your hearing changes as you get older and if a hearing aid would help you.

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