Hearing loss is one of the most common afflictions we face as we age. Age-related hearing loss, or “presbycusis,” affects about one-third of those aged 60–69 and two-thirds of those aged 70 and up. By age 100, nearly everyone has hearing loss, suggesting we’ll all experience it if we live long enough.
For most of history, hearing loss has been thought to be an annoying but relatively benign part of getting older. In recent decades, however, we’ve learned a lot about hearing loss specifically and the aging process more broadly. Hearing loss can be both an indicator of underlying problems—like hypertension or heart disease—as well as the catalyst for a host of issues. Hearing loss has been linked to memory issues, depression, loneliness, social isolation, increased risk of physical injury, decreased physical activity, and even earlier onset of cognitive decline and dementia.
Four Theories as to Why Hearing Loss Might Lead to Cognitive Decline
Atrophy of the Auditory Cortex
In the advanced stages of untreated hearing loss, the auditory cortex—the part of the brain that processes sound and interprets speech—will atrophy. It’s not that the brain cells “die” exactly, but the gray matter that supports them dissipates, and their structure collapses. This seems tied directly to underuse as a result of hearing loss. When our ears no longer send signals to our brain, the brain starts to allocate its resources elsewhere. This is a positive thing for those who are born without hearing ability, but it is also the most likely of four theories as to why hearing loss appears tied to cognitive decline when it occurs later in life.
The auditory cortex is not only responsible for interpreting sound and speech, but is closely linked to short-term memory. When we hear clearly, the auditory cortex shunts understood speech directly to short-term memory, but when we have to think more about what is being said, the path to remembering it is more circuitous. There are other ties between the auditory cortex, memory, learning, and thinking. The atrophy of the auditory cortex later in life may upset the pathways established in an adult brain to the extent that cognitive decline is the outcome.
Hearing Loss and Dementia Share a Common Cause
Another theory is that hearing loss and cognitive decline are both caused by some other process in the body. Diabetes, for example, puts people at a greater risk for both hearing loss and cognitive decline. Researchers say their studies account for these situations, and there still seems to be a more direct link suggesting that hearing loss, itself, may cause cognitive decline and dementia.
Cognitive Load
A third theory has to do with “cognitive load.” As our auditory cortex cannot get enough information to process incoming sound on its own, we engage our frontal cortex more in making sense of the heard environment. We still need to use our frontal cortex in the ways we always have, but now it is also burdened with much of the workload that the auditory cortex would have handled, as well. This extra work may overload the brain, leading to cognitive decline as a kind of exhaustion.
Social Isolation
Finally, it may be that social isolation plays a major role in the cognitive decline associated with hearing loss. People with age-related hearing loss are at significantly increased risk of social isolation. Social activity is among the most engaging things we can do with our brains. In the presence of another person, our brain lights up, firing on all cylinders and working harmoniously to communicate both visually and auditorily. In the absence of social interaction, cognitive decline seems much more likely.
Avoiding Cognitive Decline Due to Hearing Loss
The best way to help avoid cognitive decline, dementia, and other negative outcomes of untreated age-related hearing loss is to treat hearing loss! Hearing aids are the best treatment for most people. A good set of well-fitted hearing aids will not only help you better maintain your health, but will help you feel better and enjoy life more.
When asked after one year of wearing them, 95% of people say they’re glad they got hearing aids. Wearers tend to report feeling more optimistic, confident, and independent than those with untreated hearing loss. They’re not only more optimistic about their own lives but about the state of the world in general!
