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Hearing loss, part 2: Is hearing loss linked to dementia?

The Bottom Line

  • The science shows that there is a link between hearing loss and clinically significant cognitive (memory) decline, but scientists don’t yet know the reasons for the link.
  • If you have some hearing loss and go for a cognitive assessment, be sure to tell the tester about your hearing loss. The test will be more accurate if you hear as well as possible during the test.
  • Scientists don’t know yet if getting treatment for hearing problems could reduce the risk of dementia.
  • Instead of waiting years to seek help, you should consider doing something to solve your hearing problems so that you can stay active rather than avoiding situations where hearing is difficult.

In Part 1, we discussed how aging-related changes in auditory abilities and cognitive abilities (for example, memory) combine when older adults have conversations. The ear and the connections between the ear and the brain are especially important for understanding speech in noisy and busy everyday situations. When trying to follow conversation, the hearing problems of older adults can make it harder for their brains to process information. By drawing on the life-time of knowledge that is an asset for older listeners, the brain can also make it easier to follow a familiar topic. Taking advantage of knowledge to understand conversation happens even if the ears are not precisely hearing all of the sounds of a talker’s speech. Older adults activate their brains differently from younger adults when they are trying to follow conversations in daily life.

In the long term, older adults who develop clinically significant hearing loss may also develop changes in how they use their brain for listening in daily life. Such permanent changes in brain activation patterns could even be related to clinically significant cognitive declines (such as memory declines). Hearing loss may be a sign to older adults that there is more going on with their overall health. Recent epidemiological studies found an association between hearing loss and the onset of future dementia (1-7). Other recent epidemiological studies also suggest that there is an association between hearing loss and other serious health issues spanning mental health (8), physical health (9;10), falls (11), and even mortality (12-14). Although the reasons for these associations are not yet known and the results do not show that hearing loss causes dementia, it seems that people with hearing problems might need to be even more aware of what they can do to stay healthy.

In Part 2, we cover recent research suggesting that people with hearing loss may be at greater risk of developing dementia.

How common are clinically significant hearing and cognitive (memory) declines?

Clinically significant problems in hearing and cognition increase with age

In their 40s, people can start to experience more difficulty listening when it is noisy, even if listening in quiet situations is still easy. The most common way to define hearing loss is by measuring hearing thresholds (see Part 3). As we age, hearing loss increases gradually and it is one of the top three most common chronic disabilities in older adults (15). By the age of 65 years, about a 1/3 people have a clinically significant hearing loss, by the age of 75 years about half are affected, and by the age of 80 most people are affected (16).

As people get older, an increasing number will also develop clinically significant cognitive declines. These can include mild cognitive impairment or various types of dementia, of which Alzheimer’s disease is the most common. In dementia, changes in the brain are above and beyond the ‘normal’ changes in the brain that come with age. By the age of 70 years, about 1/5 of people will have a clinically significant cognitive decline (for example memory declines) due to abnormal changes in the brain (17).

Is hearing loss linked to dementia?

A growing body of epidemiological research suggests that hearing loss is more common in older people with dementia than in those with normal cognition. This research also shows that people with hearing loss are more likely to develop cognitive declines compared to people with good hearing (4;5;18-20). Indeed, some studies found that individuals with hearing loss had 2 to 5 times increased risk of developing dementia (21). In addition, for every 10 decibels (dB) increase in hearing loss individuals had a 20% increase in their risk of developing dementia (1).

In Part 1, we discussed how difficulty hearing could reduce performance on cognitive tests, such as tests of memory. Do people with hearing loss do worse on cognitive tests just because they don’t hear well during the test? Many of the tests used to diagnose dementia do involve listening to instructions. As well, some test items used to diagnose dementia involve remembering words and sentences after hearing them. It may be that the deficits on a cognitive test observed in people with hearing problems may be exaggerated. The health professional who is doing the cognitive test and the person who is being tested need to realize that part of the explanation for some of the test results could be difficulty hearing. If you think you might have some hearing loss, it would be a very good idea to have your hearing tested before going for cognitive testing. If you know that you have some hearing loss, then it is important to share this information with your doctor and other health professionals who are assessing your cognitive abilities. You should let them know if the test room is too noisy for you or if you need to use a hearing aid or other technology to ensure that you are hearing as well as possible during the test. Wearing your glasses will also help you to see better! Seeing better will help you to during tests using pictures or print materials and watching the face of the tester will make it easier for you to understand what the tester is saying.

But hearing problems are not the reason for all cognitive (memory) problems. The research discussed here in Part 2, indicates that hearing loss is associated with cognitive declines. This association occurs even for cognitive tests that do not require the person being tested to hear test items (for example, when memory for visual items is tested).

More research is needed to discover the reasons for the links between hearing loss and cognitive loss (22). Some preliminary research evidence suggests that hearing rehabilitation (such as wearing a hearing aid or having therapy) could contribute to good cognitive health (23). However, strong studies to test the link between improving one’s hearing and improving one’s cognition are just beginning. We do not yet know if there is something we can do about hearing loss that would prevent or minimize cognitive changes. In the meantime, having your hearing checked and seeking help for hearing problems as soon as possible seem to be good ideas.

Does hearing loss have other effects on my health?

Hearing loss can have wide-ranging effects on social, mental and physical health. As hearing loss progresses, eventually, people may avoid difficult listening situations by staying at home and going out less often. Importantly, promising results have been found in research investigating lifestyle factors that could increase cognitive resources (or ‘reserves’) (24). These benefits seem to result from increased social, mental and physical activities, such as being involved in social leisure activities (25), doing regular physical exercise and/or eating a healthy diet (26), or developing specialized cognitive skills or expertise such as speaking a second language (27) or playing a musical instrument (28). One of the possible explanations for the connection between hearing loss and earlier or faster cognitive decline is that people with hearing loss are less active. Thus, is will be important for researchers to learn more about how hearing rehabilitation might help older adults to remain active and healthy. People often wait ten or more years after they first notice hearing problems before they seek help from health care professionals. It may be advantageous to get help for hearing problems sooner rather than later. That is, you should seek help for your hearing loss before you stop being active and your quality of life is affected (29).

In this four-part blog post series we cover various aspects of hearing loss:

  • In part 1, we discuss how changes in hearing and cognition (for example, memory) affect communication and social interactions in healthy older adults;
  • in part 2, how hearing impairment may be related to cognitive impairment and dementia;
  • in part 3, what hearing tests can and cannot tell you about your hearing problems; and
  • and in part 4, when you should get your hearing assessed and what solutions might help you if you or your friends or family are having problems.

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Author Details

References

  1. Lin FR, Metter EJ, O'Brien RJ, Resnick SM, Zonderman AB, Ferrucci L. Hearing loss and incident dementia. Arch Neurol 2011 Feb;68(2):214-20.
  2. Lin FR, Thorpe R, Gordon-Salant S, Ferrucci L. Hearing loss prevalence and risk factors among older adults in the United States. J Gerontol A Biol Sci Med Sci 2011 May;66(5):582-90.
  3. Gates GA, Anderson ML, Feeney MP, McCurry SM, Larson EB. Central auditory dysfunction in older persons with memory impairment or Alzheimer dementia. Arch Otolaryngol Head Neck Surg 2008 Jul;134(7):771-7.
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DISCLAIMER: The blogs are provided for informational purposes only. They are not a substitute for advice from your own healthcare professionals.

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