How Hearing Loss May Affect Dementia

For another forum, I’ve written a number of articles lately about hearing loss, and thus have some idea how prevalent it is. Nearly one in five Americans has suffered some degree of hearing loss. And although this is a tragedy, a larger tragedy may be that this hearing loss is undiagnosed and untreated in an estimated 85% of those experiencing it. This makes it a kind of “hidden” disability, one with side effects that may potentially be more serious than losing one’s hearing.

Hearing loss can occur for many reasons – genetics, aging, exposure to loud noise or music, and as the result of some medications and diseases. Whatever its cause, however, in most cases the loss of hearing is gradual and “sneaks up” on people. Those with hearing loss can still in most cases hear most sounds. It’s just that certain sounds are becoming harder for them to hear, like the sounds of women’s and children’s voices, or the ability to understand conversations in noisy environments.

A very common reaction to this is that those experiencing these symptoms tend to hide their hearing loss, both from others and from themselves. People with hearing loss commonly feel that others around them are not speaking clearly, or are mumbling or speaking too softly. They may ask others to speak more loudly, but what happens more often is that they begin to “fake it,” pretending that they hear conversations that they really can’t. This can lead to a sense of frustration and isolation. People with untreated hearing loss often become less social, and stop going out to the theater or movies or to social gatherings with friends and family.

As if this social isolation weren’t bad enough in itself, new research indicates that untreated hearing loss may also cause an increased risk of dementia.

Hearing loss and dementia

Scientists at Johns Hopkins Medicine and the National Institute on Aging have recently completed a study which followed 639 subjects for nearly 12 years. They found a direct, one-to-one relationship between the subjects’ degree of hearing loss and their risk of developing dementia or Alzheimer’s disease.

Compared to subjects with normal hearing at the beginning of the study, those who had mild hearing loss were twice as likely to develop dementia, those who had moderate hearing loss were three times as likely to develop dementia, and those with severe hearing loss were five times as likely to develop dementia. For each 10-decibel decrease in their hearing ability, the risk of dementia rose by 20%. These relationships remained steady even when other conditions such as diabetes, hypertension, smoking, and other known risk factors for dementia were considered.

Dr. Frank R. Lin, lead author of the study, explains how loss of hearing could cause cognitive deficits and dementia: “People are most likely to notice communication problems when their hearing loss exceeds 25 decibels. It’s not that they can’t hear, but they can’t understand. Hearing loss at this level affects the clarity of words. The brain dedicates a lot of resources to hearing, so when the clarity of words is garbled, the brain gets a garbled message. It has to reallocate resources to hear at the expense of other brain functions.” He theorizes that the increased processing that the brain has to do to understand normal speech may deplete some of its “cognitive reserve,” the ability of healthy areas of the brain to take over when other areas lose their functionality. He points out that social isolation itself has been linked to an increased susceptibility to inflammation, which is a strongly suspected cause of dementia.

What can we do about this?

One thing we can do, if we are experiencing some symptoms of hearing loss ourselves, is seek treatment. Some forms of hearing loss (such as the buildup of cerumen or ear wax) can be easily treated, restoring our ability to hear without further treatment. Other conditions can be effectively treated with hearing aids, which can be programmed to amplify and clarify the particular sounds that an individual has trouble hearing, and to filter out background noise or the effects of tinnitus, or “ringing in the ears.”

Restoring one’s ability to hear normal conversations often has as radical effect on a person’s social life as it does on their hearing. Able to hear and participate in social gatherings again, they become more active, less depressed, and thus more likely to keep using their brains and keeping them healthy.

The link between losing one’s hearing and a greater risk of dementia has been strongly established. Whether restoring a person’s ability to hear clearly through the use of hearing aids will diminish or delay the development of dementia has not yet been proven, but it couldn’t hurt.

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Juliette Siegfried, MPH

Juliette Siegfried, MPH, has been involved in health communications since 1991. Shortly after obtaining her Master of Public Health degree, she began her career at the National Institutes of Health in Bethesda, Maryland. Juliette now lives in Europe, where she launched ServingMed(.)com, a small medical writing and editing business for health professionals all over the world.

Juliette's resume, facebook: juliette.siegfriedmph, linkedin: juliettes, (+31) 683 673 767

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