Middle-age hearing loss linked to dementia. Say again?

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The News:

Hearing loss in middle age is associated with higher odds of cognitive decline and dementia in later years, suggests a large study in Taiwan. Researchers tracked more than 16,000 men and women and found that a new diagnosis of hearing loss between ages 45 and 65 more than doubled the odds of a dementia diagnosis in the next dozen years. Even mild levels of hearing loss could be a risk factor, so hearing protection, screening and hearing aids may be important means of reducing cognitive risk as well, the study team writes in JAMA Network Open.

“Hearing loss is a potential reversible risk factor for dementia, including Alzheimer’s disease,” said senior study author Charles Tzu-Chi Lee of National Taiwan Normal University in Taipei.

Past research suggests that about two thirds of the risk for dementia is hereditary or genetic, which means about one third of the risk is from things that are modifiable, Lee noted. Among modifiable risk factors, hearing loss accounts for about 9% of dementia risk, a greater proportion than factors like hypertension, obesity, depression, diabetes and smoking.

“The early identification of hearing loss…and successful hearing rehabilitation can mitigate the negative effects of hearing loss,” Lee told Reuters. “However, the ideal time to perform hearing-loss screening to reduce the risk of dementia remains unclear.”

Lee and colleague Chin-Mei Liu of the Taiwan Centers for Disease Control analyzed data on people aged 45 and older from the National Health Insurance Research Database of Taiwan. They matched 8,135 patients newly diagnosed with hearing loss between 2000 and 2011 to 8,135 similar individuals without hearing loss and followed them all through 2013. All were free of dementia at the start, but over time, 1,868 people developed dementia–and 59% of them came from the hearing loss group.

Among people with hearing loss, new dementia cases were identified at a rate of 19 per 10,000 people, compared with 14 per 10,000 without hearing loss. Overall, hearing loss was associated with a 17% risk-increase for dementia, the researchers calculated. But when they looked at subsets of people, almost all the increased risk was concentrated in the youngest age group. Among those 45-65, dementia risk was 2.21-fold higher with hearing loss.

Steve’s Take:

Earlier in July, I met with my new primary care physician (PCP) as part of the retirement process brought about when my long-standing PCP retired. I was asked a number of questions including what I thought about my hearing. I did report increasing difficulty hearing my 20-something son in normal conversations. I also seemed to be the only one constantly needing the volume on the TV turned up while a group of us were, for example, watching a movie.

After sitting in the customary soundproof cubicle for maybe 45 minutes with the relevant set of headphones on and beeper device in my hand, the audiologist gave me an audiogram graph and said testing for my right ear indicated “normal/borderline normal hearing, sloping from mild to severe sensorineural hearing loss.” Testing for my left ear indicated “normal/borderline normal hearing, sloping from mild to [slightly more] severe hearing loss than the right.”

My audiologist’s evaluation was that I was “a borderline candidate for a hearing aid in the right ear and a [definite] candidate for hearing aid in the left year.” So I asked her, given my age, what did she think of my apparent hearing loss. Her answer was, “Perfectly normal.” She did, however, say an argument could be made that I now need a hearing aid for my left ear.

Ironically, several days later I read about a new study concluding that people who wear a hearing aid for age-related hearing problems maintain better brain function over time than those who do not. It builds on important research in recent years pulled together by the Lancet Commission on Dementia Prevention, Intervention and Care, through which hearing loss emerged as an important risk factor for dementia. This research suggests that wearing a hearing aid may mitigate that risk.

The research was conducted through the PROTECT online study of 25,000 people aged 50 or over by the University of Exeter and King’s College London, and was presented in late July at the Alzheimer’s Association International Conference in Los Angeles.

The findings provided early evidence that encouraging people to wear an effective hearing aid may help to protect their brains and reduce their risk of dementia says MedicalXpress.

Both groups undertook annual cognitive tests over two years. After that time, the group who wore hearing aids performed better in measures assessing working memory and aspects of attention than those who did not. On one attention measure, people who wore hearing aids showed faster reaction times–in everyday terms, this is a reflection of concentration; for example, “straining to hear a sound,” or “peering closely at an object of great interest,” and “listening intently to someone speaking.”

PROTECT lead researcher, Dr. Anne Corbett from the University of Exeter, said: “Previous research has shown that hearing loss is linked to a loss of brain function, memory and an increased risk of dementia. Our work is one of the largest studies to look at the impact of wearing a hearing aid and suggests that wearing a hearing aid could actually protect the brain. We now need more research and a clinical trial to test this and perhaps feed into policy to help keep people healthy in later life.”

“In an aging population, dementia will present one of the greatest challenges to society in this century,” said David Loughrey of the Trinity College Institute of Neuroscience in Dublin, who wasn’t involved in the Taiwanese study. “There are now more people over the age of 65 than under the age of 5 for the first time in human history,” he said, according to Reuters. “Pharmacological treatments for the most common cause of dementia, Alzheimer’s disease, only offer symptom-modifying effects. This has led to suggestions that a change in approach to prevention rather than treatment after diagnosis may be more beneficial.”

Future studies will investigate whether treating hearing loss can decrease the risk of dementia, the UK-based study team writes.

“Hearing health is critically important to the human experience,” said Dr. Richard Gurgel of the University of Utah in Salt Lake City, who wasn’t involved in the study. “There is more to hearing loss than just hearing. Hearing loss affects the way we fundamentally communicate and connect with one another,” he said. “Hearing loss impacts the overall health of older adults, including their emotional well-being and social isolation, as well as cognition.”

Bottom Line:

Commenting on the PROTECT study, Professor Clive Ballard of the University of Exeter Medical School said, “We know that we could reduce dementia risk by a third if we all took action from mid-life. This research is part of an essential body of work to find out what really works to keep our brains healthy. This is an early finding and needs more investigation, yet it has exciting potential. The message here is that if you’re advised you need a hearing aid, find one that works for you. At the very least it will improve your hearing and it could help keep your brain sharp, too.”

After encountering this most recent study from Taiwan researchers, essentially confirming the earlier one from the UK, my takeaway is if you are over 50, you can’t afford to run the risk of doing nothing–if you ARE experiencing hearing loss–due to the now proven correlation of it and the onset of dementia. Many of us have had experiences with dementia and AD among relatives and friends, and it is simply crushing to see people you care about literally disappear in front of your eyes.

Get your PCP to order an audiogram, and if you are experiencing hearing loss and the audiologist recommends a hearing aid, do yourself and your loved ones a big favor, and get one. I’ll be doing exactly that later this month.

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