Adults over 65 who experience vision loss have a nearly 50 percent increased risk of developing dementia. If these vision problems are corrected, that risk is dramatically reduced.
That’s according to a report released last week by an international commission focused on dementia prevention, which added visual impairment to its list of 14 modifiable risk factors for dementia. Other risk factors include smoking, diabetes, social isolation and high blood pressure.
Experts say the addition of vision loss is not a surprise, particularly considering that another sensory disability, hearing loss, has been linked to dementia and is also on the list.
Here’s what we know about how even mild to moderate vision and hearing impairment increases the risk of dementia and what to do about it.
How sensory loss can contribute to dementia
People with sensory loss receive less stimulation to the brain. Brain tissue is “use it or lose it,” so less stimulation could lead to more atrophy, said Gill Livingston, a professor of psychiatry at University College London who chaired the dementia prevention commission.
The area of the brain that processes auditory information is close to the region most affected by Alzheimer’s disease, suggesting there may be an anatomical connection. Visual information is transmitted to another part of the brain, but the way we use that information activates many different regions.
“By reducing activation in certain areas of the brain, you accelerate the rate of atrophy in those areas to some extent,” said Dr. Frank Lin, a professor of otolaryngology at the Johns Hopkins University School of Medicine. “Which, of course, has cascading effects on other areas of brain function and structure as well.”
In addition, people who experience sensory loss in later life tend to isolate themselves and not participate as much in social activities. There is evidence to suggest that loneliness can physically change a person’s brain and is a known risk factor for dementia.
“Vision loss stops you from going to the party,” said Natalie Phillips, a psychology professor at Concordia University in Montreal. “Hearing loss means you go to the party but you sit in the corner and you don’t talk to anyone.”
Hearing and vision loss may also speed up symptoms in people who are in the early stages of dementia. More brain power is needed to interpret blurred vision or confusing sounds, so fewer resources may be left for everyday memory and cognition. That can cause dementia symptoms to appear more quickly in people who were already developing the disorder, Dr. Livingston said.
Why is it so important to treat sensory loss?
Research over the past decade shows that addressing age-related vision and hearing loss has cognitive benefits.
Sight loss
Several studies have found that people with some of the most common causes of age-related vision loss, including cataracts, diabetic retinopathy and macular degeneration, are at higher risk for cognitive decline and dementia.
“We’re talking about uncorrected vision loss, meaning how much you can’t see,” Dr. Livingston explained. The magnitude of vision loss corresponds to the increased risk, she added.
While not all of these eye conditions can be reversed, when they are treated and vision is restored, the risk of developing dementia decreases. Similarly, Dr. Livingston said that people who suffer from untreated nearsightedness or farsightedness may also be at higher risk, but those who wear glasses or contact lenses to correct their vision may not be.
Supporting this, one of the studies mentioned in the commission’s report found that adults aged 65 or older who underwent cataract surgery to correct their vision had an approximately 30 percent lower risk of developing dementia compared to older adults with cataracts who did not receive the surgery.
Identifying a new risk factor for dementia is exciting, “but we’re even more excited if that risk is modifiable,” said Dr. Cecilia Lee, a professor of ophthalmology at Washington University School of Medicine who led the cataract study.
Hearing loss
Uncorrected hearing loss also carries a significant risk of dementia. The commission’s report, which compiles several studies, concluded that people with hearing loss have a 37 percent increased risk of developing dementia. The more severe the hearing loss, the greater the risk.
An estimated 63 percent of adults over the age of 70 have some degree of clinically significant hearing loss. “It’s not like we’re talking about a small portion of the population,” Dr. Lin said. “It’s almost the majority of older adults.”
Everyone’s hearing deteriorates naturally beginning in early adulthood, although in some people it deteriorates faster than in others because of genetics or exposure to loud noises, Dr. Lin said. With mild hearing loss, people have difficulty hearing sounds below 26 decibels — about the level of a whisper. Moderate hearing loss begins at 41 decibels and can make it difficult to hear normal conversations.
Hearing aids can help and appear to reduce the chance of developing dementia. People with corrected hearing loss have nearly a 20 percent lower risk of cognitive decline than people with uncorrected hearing loss. And a clinical trial published last year found that among people who were at the highest risk of cognitive decline due to age or other health conditions, those who used hearing aids for three years had significantly less cognitive decline compared with those who did not use them.
“You’re not seeing improvement per se, but you’re seeing a reduction in decline,” said James Russell Pike, a research scientist at NYU Langone Health who collaborated with Dr. Lin on the study.
What to do if you are worried
The first step is to get tested.
To assess the health of your eyes, schedule an appointment with an ophthalmologist and get a dilated eye exam once a year, Dr. Lee advised.
For a hearing test, you can go to an audiologist or ear, nose and throat specialist. Or if you want to do it at home, Dr. Lin said free hearing test apps, such as Mimi, tend to provide accurate results.
If you have hearing or vision loss, get it treated as soon as possible. Some eye conditions, such as cataracts, may require surgery, but the procedure is relatively quick and noninvasive. Correcting hearing loss is even easier since hearing aids are sold over the counter.
Addressing these issues will not only reduce the risk of dementia, but will also improve daily life, Dr. Phillips said. “The benefit of addressing them is that they improve quality of life and participation – there is nothing to lose.”
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