Recently I was invited to write an editorial referencing two studies on the effect of hearing on healthy aging. The article has just been published, in the Journals of Gerontology. Most readers won’t be able to access it, so I’m reprinting the text here. The title is “The Importance of Hearing in Maintaining Overall Functioning as We Age.” It’s a bit more formal than my posts are, and it’s edited a bit here for clarity.
As my hearing deteriorated in the decades following my initial loss at age 30, I worried that I would go deaf. Now, I worry that I will lose my cognitive faculties. The specter of dementia looms large for people with severe hearing loss. The statistical association between hearing loss, depression, and cognitive decline is well documented. What is not known is whether the association is causal, or shares a common pathogen, or is related in some other way. To explore this, a major study, the Achieve Study, is underway to see if hearing aids help reduce the risk.
The threat of cognitive decline is often cited as a reason to correct your hearing loss—to get hearing aids or cochlear implants or other hearing devices. But as people with severe hearing loss know, these do not fully correct hearing. I have worn hearing aids for more than 30 years. Twelve years ago, I replaced one aid with a cochlear implant, when the aid stopped being helpful. Certainly, I hear better with hearing aids than without. But I can hear adequately only under the best circumstances: in a quiet environment or with 1 or 2 other speakers who speak slowly and clearly. Adding even a fourth speaker to that conversation increases the likelihood of 2 people talking at once. When that happens, I cannot follow anything.
I have long worried that my corrected but far from normal hearing puts me in the same category as someone with untreated loss. One of the articles the journal asked me to comment on confirmed my suspicion. A study by Katharine K. Brewster and others from the Departments of Psychiatry and Otolaryngology at Columbia, Age-Related Hearing Loss, Late-Life Depression, and Risk of Dementia in Older Adults, studied 8529 participants. Of those 6478 were classified as having no hearing loss, 1102 as having treated hearing loss, and 949 as having untreated hearing loss. The last category included people who had hearing aids but had “hearing impairment despite hearing aid use.” All 8529 participants were free of cognitive decline at the start of the study.
Depressing but not surprising: Individuals with treated hearing loss were at higher risk for depression as well as dementia than those with no hearing loss. But, confounding expectation, they were also at higher risk than those with untreated hearing loss. As the authors wrote, “We expected treatment of hearing loss would be protective against adverse neuropsychiatric consequences.”
What could explain this? The first possibility is an error, meaning the results need to be replicated by future studies. There is also the possibility that hearing aid treatment itself has harmful effects on mood, which the authors thought unlikely. Their preferred explanation was that people who get hearing aids have hearing loss that is both more severe and of longer duration. This more severe loss increases the risk of depression and dementia. Because the efficacy of treatment was self-reported to clinicians—rather than tested audiometrically—it is also possible that some of those with treated loss were not receiving adequate hearing treatment.
The third explanation—that people with treated hearing loss usually have longer-occurring and more severe hearing loss—makes sense. Statistics show that it takes 7 years from the time of diagnosis to purchase of hearing aids, and often even once they own hearing aids many people rarely or never wear them.
But I would not discount the explanation that treatment has a harmful effect on mood.
People who pay $6 000 for hearing aids expect that they will work. They are often dismayed to find that even with their expensive new devices they still cannot hear in restaurants or places where there is background noise. They still need captions to hear TV. They still cannot hear at meetings or lectures. They are told they must buy more devices—assistive listening devices and remote mics. In addition, hearing aids can be troublesome—the batteries run out at inconvenient times or the vents get clogged with ear wax or the charger is not working properly. They are easy to lose. During the pandemic, many found that wearing a mask dislodged hearing aids, and sometimes they fell down sink drains or were lost on the street. Hearing aids by their very presence are a reminder of disability. All this can be very depressing!
It is thought that hearing loss may initiate a deleterious cascade of events including social isolation. Difficulty hearing may affect executive function and result in decreased cognitive reserve. Studies have shown atrophy of brain regions connected to auditory circuits. These “may explain the mechanistic links between hearing loss, depression, and cognitive decline,” they wrote. But the study found that depression was responsible for only 6% of the hearing–dementia relationship. “Hearing loss and depression are independent risk factors” for dementia, but how each affects the other to exacerbate cognitive decline or dementia is not clear.
Even if the mechanisms haven’t been explained, however, the authors advise that because hearing loss and memory problems and depression are so often found together, evaluation of an older patient with symptoms of cognitive decline or depression should include evaluation for hearing loss. This is a much-needed piece of advice. Currently, only 17 to 30 percent of physicians, including gerontologists, screen for hearing loss.
The second study presented here is more heartening or at least part of it is. The Association of Hearing Impairment with Higher Level Physical Functioning and Walking Endurance, an epidemiological study done by researchers at Johns Hopkins, using the long-term Baltimore Longitudinal Study of Aging. It found that hearing loss is linked to poorer physical function, including slower walking. The more severe the loss, as measured audiometrically, the greater the physical decline. The 831 participants with hearing loss, treated or not, overall scored worse in a test of physical performance and walking endurance than people with normal hearing. Over the 6 years of the study, they showed faster rates of decline than participants with normal hearing or mild hearing loss. Vestibular dysfunction was factored in. But, and here is the encouraging news, hearing aid users—regardless of the severity of their loss—walked significantly faster than nonusers.
The authors acknowledged that their study population was more likely to be white and have higher socioeconomic status, both associated with better physical function, than the general population. In addition, hearing aid use was self-reported with answers limited to Yes or No on whether they used hearing aids. But it is still a tantalizing finding. The authors suggest that social isolation, cognitive impairment, and reduced physical activity may play a greater role among the non-hearing aid users. Auditory clues can contribute to balance, and uncorrected hearing loss might affect vestibular function. There is also the possibility that hearing loss and poor physical performance have a common cause.
Another possible explanation occurred to me as I was reading this study. Treating hearing loss takes initiative. People who get hearing aids often must overcome hurdles like lack of access to good hearing health care as well as significant expense, because hearing aids are not covered by most health insurance, including Medicare. Maybe this same initiative contributes to better physical self-care. Just as they have taken the initiative to buy and wear hearing aids, the better performers may have tried to stay healthy in other ways, including diet and exercise.
One takeaway from both these studies is that exercise is good for you. Exercise can ease symptoms of depression (an established risk factor for cognitive decline). The finding that hearing aid users walked longer and faster than nonusers, regardless of the severity of their loss, suggests that “screening for and treatment of hearing loss may delay or slow progression of hearing-related physical decline.” In other words, get your hearing tested and treated, and your overall physical health may benefit.