Have you ever felt like your brain was working just a bit too hard? You know, those days where you’re juggling dozens of things, yet somehow you manage to get them all done.
While it may be just a little overwhelming, it’s days like this that show you just how powerful your brain really is.
And with all that your brain is capable of, it does unfortunately have its limits. Which is why it should come as no surprise that several recent studies have shown a link between a reduction in sensory functions like vision and hearing to an overall decline in cognitive abilities.
And while researchers aren’t exactly sure why this connection exists, there is a growing body of evidence that suggests vision and hearing deficits that go uncorrected can speed up the rate of cognitive decline.
According to National statistics the number of Americans with poor vision, which is less likely to be detected in older adults, is expected to double by the year 2050. Hearing loss, another under diagnosed and under treated problem in the elderly currently affects approximately two-thirds of adults over 70. Combined, both hearing and visual impairments occur at a rate of one in nine for those over the age of 80. Add these statistics to the fact that the rate of dementia is now doubling every 20 years and there appears to be a connection.
In one recent study, published in JAMA Ophthalmology, researchers found a correlation between poor vision and cognitive decline.1
The study showed consistent findings across all measurements and researchers concluded that an association between vision impairment and compromised brain function is a very real finding.
The lead author, Dr. Suzann Pershing, ophthalmologist at Stanford University School of Medicine, said that “while this association doesn’t prove vision loss causes cognitive decline, intuitively it makes sense that the less engaged people are with the world, the less cognitive stimulation they receive, and the more likely their cognitive function will decline.”
In a previous study performed at the University of Michigan, the study’s authors Dr. Mary A.M. Rogers and Kenneth M. Langa found that test subjects with poor vision had a 63 percent greater risk of developing dementia over a period of eight and a half years.2
They also discovered that those suffering from poor vision, who did not visit an ophthalmologist were five times more likely to experience cognitive decline and nine and a half times more likely to develop Alzheimer’s disease.
“This is not necessarily a one-way relationship,” Dr. Pershing said. “If you improve the vision of people with cognitive impairment, they can function better.”
But it isn’t just vision, because researchers are also beginning to see a correlation between hearing loss and cognitive decline as well.
At this point, researchers are still uncertain that wearing properly adjusted hearing aids does anything to decrease the risk of dementia or slow its onset. However, one ongoing study sponsored by the National Institute on Aging should be able to answer that question in the next few years. They’re looking at whether using hearing aids can help preserve brain function in people with hearing loss as they age.3
According to Dr. Frank R. Lin an otolaryngologist at the Johns Hopkins Center on Aging and Health, “the potential impact is huge,” especially now.
While researchers wait for the results, there are some things they already know.
In a 2013 study published in JAMA Internal Medicine Dr. Lin led a team that looked at the relationship between hearing loss and cognitive decline in 1,984 adults.4
What they discovered is that those with hearing loss were 24 percent more likely than others their age with normal hearing to suffer from cognitive decline within six years.
Overall, their level of cognitive decline was 40 percent faster than those with normal hearing. They also had more problems with other higher-level brain functions, including thinking and memory, which occurred on average approximately three years prior to those who didn’t have hearing problems. In addition, the more severe their hearing loss at the beginning of the study the more severe their cognitive decline was overtime.
“Older adults with hearing loss face an increased risk of dementia even when you control for diseases like diabetes and high blood pressure,” Dr. Lin said in an interview. “So we think they’re causally related.”
Dr. Lin suggested three ways that may explain why poor hearing and dementia are connected.
The first is what is known as “cognitive load” — when you have difficulty hearing your brain receives messages that are hard to decipher, forcing it to work much harder.
Another possibility is the fact that those suffering from hearing loss may withdraw and stop interacting with other people. This reduced social interaction may result in less cognitive stimulation overall.
Finally, and possibly the most important potential explanation involves the structure of the brain itself. A loss of hearing results in a faster rate of overall brain atrophy in the areas involved in hearing, which also happen to be involved in functions like memory, learning and thinking.
In a previous study done at Washington University in St. Louis, Jonathan Peelle and colleagues were able to show through a series of functional M.R.I’s that even a mild loss of hearing can cause people to “recruit more of their frontal cortex,” which means that the part of the brain needed for thinking and decision-making is overworked when trying to understand speech.5
“Even in young adults with clinically normal hearing,” says Dr. Peelle, “just a small decline in how well they hear engages more of their frontal cortex.”
He went on to say, when hearing loss is advanced, studies have shown that the auditory cortex shrinks, which may diminish the brain’s ability to perform tasks other than hearing.
While it remains unclear how cost effective regular screenings actually are, there appears to be a strong consensus that periodic exams would in fact diminish the risk of dementia and potentially improve quality of life.
The American Academy of Ophthalmology recommends that people between the ages of 40 and 54 with no symptoms or risk factors for vision loss get a comprehensive eye exam every two to four years. And then every one to three years for people between the ages of 55 and 64, moving to every year or two past age 65.
These routine exams can help to preserve vision by detecting problems that are treatable like glaucoma, cataracts and age-related macular degeneration.
The American Speech-Language-Hearing Association recommends a hearing test “at least every decade through age 50 and every three years thereafter.” As Dr. Lin explained, hearing loss can occur so gradually that people don’t even realize there is a problem until its so severe, that it may be too late.