Brain Health and Sensory Health: A Two-Way Street

Recent research offers new insights into the complicated connections between our five senses and the risk of dementia.

Symbolic drawing of brain and four senses

A senior experiences hearing loss, or visual impairment, or a lessened sense of smell ā€¦ and, at the same time, memory loss and thinking problems. Coincidence? If not, what's the connection? Does sensory loss raise the risk of dementia? Do the brain changes of dementia weaken the senses? Might sensory loss and dementia sometimes have a common biological cause? Could sensory changes even provide an early clue that a person has Alzheimer's disease?

Ongoing research is tackling these questions. In a June 2018 study, David Lee, Ph.D., of the University of Miami Miller School of Medicine released new evidence confirming that vision loss is bad for brain health. "We found that the rate of worsening vision was associated with the rate of declining cognitive function, and that vision has a stronger influence on cognition than the other way around," Lee said. "The takeaway is that we need to pay more attention to preventing and treating vision loss to possibly reduce the rate of cognitive decline."

"As we live longer, sensory and cognitive impairments will become more prevalent," said Dr. Heather Whitson, Associate Professor of Ophthalmology at Duke University Medical Center. "While we know a great deal about these impairments individually, we know less about how they are related ā€” which is surprising, since impaired hearing and vision often go hand in hand and are associated with an increased risk for cognitive trouble."

Dr. Whitson took part in a major medical conference on this topic hosted in September 2018 by the American Geriatrics Society. Participants noted that science has only scratched the surface of the "two-way street" connecting sensory and cognitive health. They explored ways to prevent sensory loss, and discussed adaptive strategies to keep people with sensory loss active and healthy.

Why can sensory loss lead to cognitive impairment?

For one thing, loss of hearing and vision make it harder to get enough of the mental stimulation that supports brain function. Sensory loss also creates barriers to managing health conditions that are bad for the brain, such as diabetes and heart disease. And there's another major reason, explained Dr. Asri Maharani of the University of Manchester in the U.K. "It's not really certain why hearing and visual problems have an impact on cognitive decline, but I'd guess that isolation, stigma and the resultant lack of physical activity that are linked to hearing and vision problems might have something to do with it."

But Dr. Maharani's team had good news to offer. In October 2018, they released the results of two studies, each on more than 2,000 people, showing that treating sensory loss can dramatically slow the rate of age-related cognitive decline. Cataract surgery slowed the progression of memory loss in study subjects by 50 percent, and equipping seniors with hearing aids cut the decline by 75 percent!

How can we protect our vision and hearing?

Many eye diseases are common as we age. These include glaucoma, cataracts, age-related macular degeneration, diabetic eye disease and retinal problems. Even in the absence of these conditions, normal age-related changes in vision make it harder to see clearly. Regular eye checkups can catch a problem early, often before symptoms are obvious. Today many eye conditions can be treated. And even if some or all vision is lost, vision rehabilitation and adaptive devices can keep people with vision loss active and engaged.

Senior woman having her hearing tested

Our hearing, too, declines with age, and for many of us, a lifetime of exposure to loud noises has made things worse. Have your hearing checked regularly, and if your doctor recommends hearing aids, get them and stick with it through the adjustment process. The University of Manchester researchers reported that some seniors feel there's a stigma attached to wearing hearing aids, but the team hopes that baby boomers will be more motivated by today's more contemporary, high-tech models.

What about the other senses?

While vision and hearing get most of the attention, all five of our senses contribute to brain health. Smell is particularly interesting. Studies show that loss of smell can be an early sign of Alzheimer's disease. Smell and taste work together to provide information about things we eat and substances around us. While taste and smell diminish naturally with age, we can avoid certain things that hasten the loss, such as poor diet, infections, pollution and other toxic substances in the air, and sleep disorders such as sleep apnea.

Our sense of touch also provides information that helps our brains interact with our surroundings. As we grow older, decreased blood flow to the nerve endings, spinal cord and brain may result in decreased sensations of pain, temperature, pressure and texture. Diabetes, vitamin deficiencies, skin diseases and other health problems also can affect the sense of touch. Changes should be reported to the doctor.

One thing all the researchers agree about: Treating sensory loss could slow the rate of dementia in the U.S. ā€” and the accompanying multibillion-dollar price tag for dementia care, which is far higher than treating vision loss and paying for hearing aids.


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