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Hearing Loss and Dementia

The Problem

An increasing number of independent scientific studies are showing strong evidence that hearing loss is more than just a nuisance of aging. The message is disturbing: people who experience hearing loss as they age may also have a significantly higher risk of developing cognitive disorders, including dementia. Cognitive function is an intellectual process that allows us to become aware of, perceive, or comprehend ideas. It involves all aspects of perception, thinking, reasoning, and memory.

The Evidence

A 2011 study (Hearing Loss and Incident dementia) was conducted by researchers at Johns Hopkins University School of Medicine in Baltimore in partnership with the National Institute on Aging. Dr. Frank Lin and others found that older adults with hearing loss were more likely to develop cognitive problems than others who retained normal hearing as they aged, and the risk of developing dementia increased with the degree of hearing loss. The study found that people with severe hearing loss were five times more likely to develop cognitive problems, and even mild hearing loss doubled the risk for serious cognitive impairment Las Vegas.

In a follow-up study (Hearing Loss and Cognitive Decline in Older Adults, 2013) Dr. Lin and colleagues substantiated that older adults with hearing loss were more likely to develop thinking and memory problems than older adults with normal hearing, and the degree of cognitive degeneration was directly related to the amount of hearing loss. The study found that cognitive capabilities for those with hearing loss declined 30 to 40 percent faster than they did for a group with normal hearing. According to Dr. Lin, The results of the study should prompt an effort to make age-related hearing loss a public health priority.

Other studies indicate that hearing loss accelerates atrophy in auditory areas of the brain, making it more difficult for older adults to comprehend speech. “Your hearing ability directly affects how the brain processes sounds, including speech,” says Dr. Jonathon Peelle, PhD, research associate in the Department of Neurology at the University of Pennsylvania. “Preserving your hearing doesn’t only protect your ears, but also helps your brain perform at its best.”

Pathways to Dementia

Although the studies could not determine a direct link from hearing loss to cognitive degeneration, researchers proposed several pathways that could lead from hearing loss to dementia, and these are summarized in the figure. The first pathway (gold arrows) is known as “cognitive load.” As hearing loss progresses, the brain must devote greater resources to auditory processing (speech and sound) at the detriment of thinking and memory. Another pathway (blue arrows) leads from hearing loss to social isolation, prompted by increasing communication difficulties. Social isolation has been well established in previous research as a risk factor for cognitive decline. A third pathway (green arrows) is known as auditory deprivation. When the hearing nerves and regions of the brain responsible for hearing are deprived of sound, they atrophy, a process that can accelerate the onset of dementia. An argument could be made that some other, yet-to-be-determined physiologic factor may serve as a common cause for both hearing loss and dementia, but many researchers agree that there is strong evidence to support a causative link from hearing loss to significant cognitive decline in older adults.

Epilogue

Although we don’t have clear evidence that hearing aids, cochlear implants and other rehabilitative measures will reduce or prevent cognitive degeneration, many clinical researchers are convinced that these interventions improve the lives of their patients. As Dr. Lin noted, “they are able to engage again: they
are no longer isolated.”  So…there are no downsides to treatment…but there may be serious downsides to letting hearing loss go full course!