By Dana G. SmithThe New York Times
Adults over the age of 65 who have vision loss have an almost 50% higher risk of developing dementia. If these vision problems are corrected, this risk decreases significantly.
That’s according to a report released this month by an international commission 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 comes as no surprise, especially since another sensory impairment – 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 loss increases the risk of dementia and what to do about it.
How Sensory Loss Can Contribute to Dementia
People with sensory impairment receive fewer signals in their brains. Brain tissue is “use it or lose it,” so less stimulation could lead to more atrophy, said Gill Livingston, professor of psychiatry at University College London, who led 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 link. Visual information is transmitted to another part of the brain, but the way we use that information activates many different regions.
“As activation in certain areas of the brain decreases, you see those areas atrophy more rapidly, to some extent,” says Frank Lin, MD, professor of otolaryngology at the Johns Hopkins University School of Medicine. “You can imagine that this has cascading effects on other areas of brain function and structure as well.”
Additionally, people who experience sensory loss as adults tend to become withdrawn and less socially engaged. Studies suggest that loneliness can physically change a person’s brain and is a known risk factor for dementia.
“Vision loss prevents you from going to the party,” says 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 don’t talk to anyone.”
Hearing and vision loss may also accelerate symptoms in people in the early stages of dementia. It takes more brain power to interpret blurry vision or garbled sounds, reducing the resources available for everyday memory and cognition. This can lead to a faster onset of dementia symptoms in people who already had the disease, Livingston said.
Why treating sensory loss is so crucial
Research over the past decade shows that addressing age-related vision and hearing loss has cognitive benefits.
Vision 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 increased risk of cognitive decline and dementia.
“We’re talking about uncorrected vision loss, which is the amount of vision you don’t see,” Livingston explained. The amount of vision loss corresponds to the increased risk, she added.
While not all of these eye diseases are reversible, when they are treated and vision is restored, the risk of dementia decreases. Similarly, Livingston said that people with untreated farsightedness or nearsightedness may also be at increased risk, but not those who wear glasses or contact lenses to correct their vision.
To support this, one of the studies cited in the commission’s report found that adults aged 65 and older who had cataract surgery to correct their vision had about a 30% lower risk of developing dementia than older adults with cataracts who had not had 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, professor of ophthalmology at the University of Washington 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 combined several studies, found that people with hearing loss have a 37% increased risk of developing dementia. The more severe the hearing loss, the higher the risk.
An estimated 63% of adults over the age of 70 have clinically significant hearing loss. “It’s not like we’re talking about a tiny portion of the population,” Lin said. “This is almost the majority of older adults.”
Everyone’s hearing naturally deteriorates starting in early adulthood, although some people decline more quickly than others due to genetic factors or exposure to loud noises, Lin said. With mild hearing loss, people have trouble hearing sounds below 26 decibels, about the level of a whisper. Moderate hearing loss starts at 41 decibels and can make it difficult to listen to normal conversations.
Hearing aids can help and appear to reduce the risk of developing dementia. People with corrected hearing loss have a nearly 20% lower risk of cognitive decline than people with uncorrected hearing loss. A clinical trial published last year found that among people at highest risk of cognitive decline due to age or other health problems, those who wore hearing aids for three years had significantly less cognitive decline than those who did not.
“You don’t see improvement per se, but you see a reduction in decline,” said James Russell Pike, a research scientist at NYU Langone Health who collaborated with 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, make an appointment with an eye doctor and have a dilated eye exam once a year, Lee advises.
For a hearing test, you can visit an audiologist or ENT specialist. Or if you want to do it at home, free hearing test apps, such as Mimi, tend to provide accurate results.
If you have hearing or vision loss, seek treatment 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 available over the counter.
By addressing these issues, you’ll not only reduce your risk of dementia, but you’ll also improve your daily life, Phillips said. “You know, there’s nothing to lose by addressing this issue in terms of quality of life and engagement.”
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