The Links Between Hearing Loss and Dementia

Currently, there is no known reason as to exactly why hearing loss seems to increase your chances of getting dementia so greatly, but there are many different theories being bounced around.
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Do you find that, lately, your ability to hear has been deteriorating somewhat? When you're with your friends at the pub or sitting with your partner in front of the television, are you finding it more difficult to catch what's just been said?

If so, then I'm afraid we have some potentially disturbing news for you: A 2011 study found that hearing loss may increase your chances of developing dementia.

Researchers from the John Hopkins School of Medicine in Baltimore partnered up with a handful of other research institutions from across the United States to conduct their experiment, which looked at 639 different adults aged between 36 and 90 years old.

Between the years of 1990 and 1994, these adults underwent a series of tests to determine their cognitive and aural health and were monitored until the end of May of 2008. During these years, the researchers followed any potential development of Alzheimer's and dementia.

Of these 639, none had dementia at the start of the study, 125 had a "mild" hearing loss (between 25 and 40 decibels lost), 53 had a hearing loss described as "moderate" (from 41 to 70) and a final 6 suffered from a "severe" hearing loss. These latter six lost more than 70 decibels' worth of hearing. The remaining 455 participants could hear perfectly.

A mid-progress report was followed up after roughly 12 years -- after that period, it was found that 58 of the initial 639 (or just more than 9 percent) had been diagnosed as suffering from dementia, and 37 of these were Alzheimer's.

It was found that those who suffered from hearing loss at the beginning of the study were more likely to develop dementia -- the greater the hearing loss, the more chance there was. There was a noticeable trend for the Alzheimer's, too: Baltimore's Dr. Frank Lin reported that for every 10 decibels of hearing lost, the extra likelihood of development jumped up by 20 percent.

The risk was worst for those participants who were aged 60 or older -- 36 percent of the dementia risk was recorded as being associated with the hearing loss.

Sadly, this research has recently been backed up by another, completely independent study. In January of this year, a study of 1984 adults was completed, after having run since 1997. It came out with similar results, but came with a few additional snippets of information.

Firstly, it provided the rate of decay -- it was discovered that people who suffer from hearing loss would typically experience a loss of memory and thinking capabilities an estimated 40 percent faster than those who have no hearing problems.

Another rather depressing finding was that no significant decrease of the dementia risk is brought about by the use of hearing aids, so that potential solution is a lost cause.

Currently, there is no known reason as to exactly why hearing loss seems to increase your chances of getting dementia so greatly, but there are many different theories being bounced around. These theories are wide in range, stretching from the fairly banal but believable ("cognitive overload," i.e., the brain tires itself out because it has to overcompensate to hear things) to the possibility that hearing loss is actually an indicator rather than a contributing factor -- the loss of the lower frequency sounds could act as a "warning sign" for vascular problems, which would cause both hearing loss and dementia.

Other potential reasons include that hearing loss would lead to a certain amount of social isolation in life, which could potentially contribute to the decline of mental faculties that is dementia. The final theory is that they are simply linked, as in they are caused by similar things or involve similar processes.

This last theory in particular could actually, if it turned out to be true, bring with it some good news: If the two symptoms share similar causes or processes, this could lead to early interventional methods against dementia being discovered.

For now, the results are unknown, but these studies will prove to be invaluable in the coming years. If they help to further research into a potential Alzheimer's cure (or even vaccine, so to speak), then the agony of this debilitating condition could be something of the past.

Tom Rokins writes on behalf of Boots Hearingcare, one of the UK's largest suppliers of digital hearing aids.

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