hearing loss

Hearing aid use linked to better cognition in hearing-impaired elderly

  • A study of older adults with impaired hearing supports the use of hearing aids to help fight the development of cognitive decline and dementia.

A study involving 100 older adults (aged 80-99) with hearing loss has found that those who used a hearing aid performed significantly better on a cognitive test (MMSE) than those who didn't use a hearing aid, despite having poorer hearing. Among non-users, participants with more hearing loss had lower MMSE scores than those with better hearing.

In the MMSE, participants give vocal responses to verbal commands. Executive function was also assessed with the Trail Making Test, Part B, which doesn't have a verbal or auditory component. On this test, although hearing aid users performed better than non-users, the difference was not statistically significant. Nor were scores correlated with hearing level.

The finding suggests that hearing loss is associated with sensory-specific cognitive decline rather than global cognitive impairment.

Of the 100 participants, 34 regularly used a hearing aid.

Previous studies have found hearing loss is associated with greater cognitive decline in older adults. A physician recently told the annual meeting of the American Association for the Advancement of Science (AAAS) that as much as 36% of dementia risk might be attributable to hearing impairment, and urged that doctors treat age-related hearing impairment more seriously.

The finding supports the view that use of hearing aids for the hearing impaired may help keep them more socially engaged, thus preventing or slowing the progression of cognitive decline and the development of dementia.

More than half of adults over age 75 have hearing loss, yet less than 15% of the hearing impaired use a hearing aid.

http://www.eurekalert.org/pub_releases/2016-04/cumc-hau042216.php

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It’s not the noise in the brain; it’s the noise in the input

A new study has found that errors in perceptual decisions occurred only when there was confused sensory input, not because of any ‘noise’ or randomness in the cognitive processing. The finding, if replicated across broader contexts, will change some of our fundamental assumptions about how the brain works.

05/2013

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Hearing loss accelerates cognitive decline in older adults

February, 2013

A large study finds that hearing loss significantly increases the rate of cognitive decline in old age.

I’ve written before about the gathering evidence that sensory impairment, visual impairment and hearing loss in particular, is a risk factor for age-related cognitive decline and dementia. Now a large long-running study provides more support for the association between hearing loss and age-related cognitive decline.

The study involved 1,984 older adults (aged 75-84) whose hearing and cognition was tested at the start of the study, with cognitive performance again assessed three, five, and six years later.

Those with hearing loss showed significantly faster cognitive decline than those with normal hearing — some 30-40% faster (41% on the MMSE; 32% on the Digit Symbol Substitution Test), with rate directly related to the amount of hearing loss.

On average, older adults with hearing loss developed significant cognitive impairment 3.2 years sooner than those with normal hearing — a very significant difference indeed.

It has been suggested that increasing social isolation and loneliness may underlie some, if not all, of this association. It may also be that difficulties in hearing force the brain to devote too much of its resources to processing sound, leaving less for cognition. A third possibility is that some common factor underlies both hearing loss and cognitive decline — however, the obvious risk factors, such as high blood pressure, diabetes and stroke, were taken account of in the analysis.

The findings emphasize the importance of getting help for hearing difficulties, rather than regarding them as ‘natural’ in old age.

Reference: 

[3293] Lin FR, Yaffe K, Xia J, et al. Hearing loss and cognitive decline in older adults. JAMA Internal Medicine [Internet]. 2013 :1 - 7. Available from: http://dx.doi.org/10.1001/jamainternmed.2013.1868

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Childhood music training has enduring benefits for hearing

September, 2012

More evidence that learning a musical instrument in childhood, even for a few years, has long-lasting benefits for auditory processing.

Adding to the growing evidence for the long-term cognitive benefits of childhood music training, a new study has found that even a few years of music training in childhood has long-lasting benefits for auditory discrimination.

The study involved 45 adults (aged 18-31), of whom 15 had no music training, 15 had one to five years of training, and 15 had six to eleven years. Participants were presented with different complex sounds ranging in pitch while brainstem activity was monitored.

Brainstem response to the sounds was significantly stronger in those with any sort of music training, compared to those who had never had any music training. This was a categorical difference — years of training didn’t make a difference (although some minimal length may be required — only one person had only one year of training). However, recency of training did make a difference to brainstem response, and it does seem that some fading might occur over long periods of time.

This difference in brainstem response means that those with music training are better at recognizing the fundamental frequency (lowest frequency sound). This explains why music training may help protect older adults from hearing difficulties — the ability to discriminate fundamental frequencies is crucial for understanding speech, and for processing sound in noisy environments.

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[3074] Skoe E, Kraus N. A Little Goes a Long Way: How the Adult Brain Is Shaped by Musical Training in Childhood. The Journal of Neuroscience [Internet]. 2012 ;32(34):11507 - 11510. Available from: http://www.jneurosci.org/content/32/34/11507

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Music training protects against aging-related hearing loss

February, 2012

More evidence that music training protects older adults from age-related impairment in understanding speech, adding to the potential benefits of music training in preventing dementia.

I’ve spoken before about the association between hearing loss in old age and dementia risk. Although we don’t currently understand that association, it may be that preventing hearing loss also helps prevent cognitive decline and dementia. I have previously reported on how music training in childhood can help older adults’ ability to hear speech in a noisy environment. A new study adds to this evidence.

The study looked at a specific aspect of understanding speech: auditory brainstem timing. Aging disrupts this timing, degrading the ability to precisely encode sound.

In this study, automatic brain responses to speech sounds were measured in 87 younger and older normal-hearing adults as they watched a captioned video. It was found that older adults who had begun musical training before age 9 and engaged consistently in musical activities through their lives (“musicians”) not only significantly outperformed older adults who had no more than three years of musical training (“non-musicians”), but encoded the sounds as quickly and accurately as the younger non-musicians.

The researchers qualify this finding by saying that it shows only that musical experience selectively affects the timing of sound elements that are important in distinguishing one consonant from another, not necessarily all sound elements. However, it seems probable that it extends more widely, and in any case the ability to understand speech is crucial to social interaction, which may well underlie at least part of the association between hearing loss and dementia.

The burning question for many will be whether the benefits of music training can be accrued later in life. We will have to wait for more research to answer that, but, as music training and enjoyment fit the definition of ‘mentally stimulating activities’, this certainly adds another reason to pursue such a course.

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Common health complaints increase Alzheimer's risk

October, 2011

Two large studies respectively find that common health complaints and irregular heartbeat are associated with an increased risk of developing Alzheimer’s, while a rat study adds to evidence that stress is also a risk factor.

A ten-year study involving 7,239 older adults (65+) has found that each common health complaint increased dementia risk by an average of about 3%, and that these individual risks compounded. Thus, while a healthy older adult had about an 18% chance of developing dementia after 10 years, those with a dozen of these health complaints had, on average, closer to a 40% chance.

It’s important to note that these complaints were not for serious disorders that have been implicated in Alzheimer’s. The researchers constructed a ‘frailty’ index, involving 19 different health and wellbeing factors: overall health, eyesight, hearing, denture fit, arthritis/rheumatism, eye trouble, ear trouble, stomach trouble, kidney trouble, bladder control, bowel control, feet/ankle trouble, stuffy nose/sneezing, bone fractures, chest problems, cough, skin problems, dental problems, other problems.

Not all complaints are created equal. The most common complaint — arthritis/rheumatism —was only slightly higher among those with dementia. Two of the largest differences were poor eyesight (3% of the non-demented group vs 9% of those with dementia) and poor hearing (3% and 6%).

At the end of the study, 4,324 (60%) were still alive, and of these, 416 (9.6%) had Alzheimer's disease, 191 (4.4%) had another sort of dementia and 677 (15.7%) had other cognitive problems (but note that 1,023 were of uncertain cognitive ability).

While these results need to be confirmed in other research — the study used data from broader health surveys that weren’t specifically designed for this purpose, and many of those who died during the study will have probably had dementia — they do suggest the importance of maintaining good general health.

Common irregular heartbeat raises risk of dementia

In another study, which ran from 1994 to 2008 and followed 3,045 older adults (mean age 74 at study start), those with atrial fibrillation were found to have a significantly greater risk of developing Alzheimer’s.

At the beginning of the study, 4.3% of the participants had atrial fibrillation (the most common kind of chronically irregular heartbeat); a further 12.2% developed it during the study. Participants were followed for an average of seven years. Over this time, those with atrial fibrillation had a 40-50% higher risk of developing dementia of any type, including probable Alzheimer's disease. Overall, 18.8% of the participants developed some type of dementia during the course of the study.

While atrial fibrillation is associated with other cardiovascular risk factors and disease, this study shows that atrial fibrillation increases dementia risk more than just through this association. Possible mechanisms for this increased risk include:

  • weakening the heart's pumping ability, leading to less oxygen going to the brain;
  • increasing the chance of tiny blood clots going to the brain, causing small, clinically undetected strokes;
  • a combination of these plus other factors that contribute to dementia such as inflammation.

The next step is to see whether any treatments for atrial fibrillation reduce the risk of developing dementia.

Stress may increase risk for Alzheimer's disease

And a rat study has shown that increased release of stress hormones leads to cognitive impairment and that characteristic of Alzheimer’s disease, tau tangles. The rats were subjected to stress for an hour every day for a month, by such means as overcrowding or being placed on a vibrating platform. These rats developed increased hyperphosphorylation of tau protein in the hippocampus and prefrontal cortex, and these changes were associated with memory deficits and impaired behavioral flexibility.

Previous research has shown that stress leads to that other characteristic of Alzheimer’s disease: the formation of beta-amyloid.

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Childhood musical training helps auditory processing in old age

June, 2011

Another study confirms the cognitive benefits of extensive musical training that begins in childhood, at least for hearing.

A number of studies have demonstrated the cognitive benefits of music training for children. Now research is beginning to explore just how long those benefits last. This is the second study I’ve reported on this month, that points to childhood music training protecting older adults from aspects of cognitive decline. In this study, 37 adults aged 45 to 65, of whom 18 were classified as musicians, were tested on their auditory and visual working memory, and their ability to hear speech in noise.

The musicians performed significantly better than the non-musicians at distinguishing speech in noise, and on the auditory temporal acuity and working memory tasks. There was no difference between the groups on the visual working memory task.

Difficulty hearing speech in noise is among the most common complaints of older adults, but age-related hearing loss only partially accounts for the problem.

The musicians had all begun playing an instrument by age 8 and had consistently played an instrument throughout their lives. Those classified as non-musicians had no musical experience (12 of the 19) or less than three years at any point in their lives. The seven with some musical experience rated their proficiency on an instrument at less than 1.5 on a 10-point scale, compared to at least 8 for the musicians.

Physical activity levels were also assessed. There was no significant difference between the groups.

The finding that visual working memory was not affected supports the idea that musical training helps domain-specific skills (such as auditory and language processing) rather than general ones.

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Hearing loss and dementia linked

March, 2011

Another study builds on earlier indications that hearing loss is a risk factor for dementia, and emphasizes the need for early intervention.

Data from the Baltimore Longitudinal Study on Aging, begun in 1958, has revealed that seniors with hearing loss are significantly more likely to develop dementia than those who retain their hearing. The study involved 639 people whose hearing and cognitive abilities were tested between 1990 and 1994, then re-tested every one to two years. By 2008, 58 (9%) of them had developed dementia (37 of which were Alzheimer’s).

Those with hearing loss at the beginning of the study were significantly more likely to have developed dementia. The degree of hearing loss also correlated with greater risk: those with mild, moderate, and severe hearing loss had twofold, threefold, and fivefold, respectively, the risk of developing dementia over time. The association was maintained after other risk factors, (high blood pressure, smoking, education, age, sex, race) were taken into account.

The reason for the association is not yet known. It’s possible that a common pathology may underlie both, or that the strain of decoding sounds over the years may make the brain more vulnerable to dementia, or that hearing loss makes people more socially isolated (a known risk factor for dementia).

The findings do suggest that hearing loss should be regarded more seriously, and not simply accepted as a natural part of growing old.

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How the deaf have better vision; the blind better hearing

November, 2010

Two recent studies point to how those lacking one sense might acquire enhanced other senses, and what limits this ability.

An experiment with congenitally deaf cats has revealed how deaf or blind people might acquire other enhanced senses. The deaf cats showed only two specific enhanced visual abilities: visual localization in the peripheral field and visual motion detection. This was associated with the parts of the auditory cortex that would normally be used to pick up peripheral and moving sound (posterior auditory cortex for localization; dorsal auditory cortex for motion detection) being switched to processing this information for vision.

This suggests that only those abilities that have a counterpart in the unused part of the brain (auditory cortex for the deaf; visual cortex for the blind) can be enhanced. The findings also point to the plasticity of the brain. (As a side-note, did you know that apparently cats are the only animal besides humans that can be born deaf?)

The findings (and their broader implications) receive support from an imaging study involving 12 blind and 12 sighted people, who carried out an auditory localization task and a tactile localization task (reporting which finger was being gently stimulated). While the visual cortex was mostly inactive when the sighted people performed these tasks, parts of the visual cortex were strongly activated in the blind. Moreover, the accuracy of the blind participants directly correlated to the strength of the activation in the spatial-processing region of the visual cortex (right middle occipital gyrus). This region was also activated in the sighted for spatial visual tasks.

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Benefits of music training on the brain

August, 2010

A comprehensive review of the recent research into the benefits of music training on learning and the brain concludes music training in schools should be strongly supported.

A review of the many recent studies into the effects of music training on the nervous system strongly suggests that the neural connections made during musical training also prime the brain for other aspects of human communication, including learning. It’s suggested that actively engaging with musical sounds not only helps the plasticity of the brain, but also helps provide a stable scaffolding of meaningful patterns. Playing an instrument primes the brain to choose what is relevant in a complex situation. Moreover, it trains the brain to make associations between complex sounds and their meaning — something that is also important in language. Music training can provide skills that enable speech to be better heard against background noise — useful not only for those with some hearing impairment (it’s a common difficulty as we get older), but also for children with learning disorders. The review concludes that music training tones the brain for auditory fitness, analogous to the way physical exercise tones the body, and that the evidence justifies serious investment in music training in schools.

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[1678] Kraus N, Chandrasekaran B. Music training for the development of auditory skills. Nat Rev Neurosci [Internet]. 2010 ;11(8):599 - 605. Available from: http://dx.doi.org/10.1038/nrn2882

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