Hearing loss has long been considered a normal, and thus acceptable, part of aging. It is common: Estimates suggest that it affects two out of three adults age 70 and older. It is also rarely treated. In the U.S., only about 14 percent of adults who have hearing loss wear hearing aids. An emerging body of research, however, suggests that diminished hearing may be a significant risk factor for Alzheimer’s disease and other forms of dementia — and that the association between hearing loss and cognitive decline potentially begins at very low levels of impairment.
In November, a study published in the journal JAMA Otolaryngology — Head and Neck Surgery examined data on hearing and cognitive performance from more than 6,400 people 50 and older. Traditionally, doctors diagnose impairment when someone experiences a loss in hearing of at least 25 decibels, a somewhat arbitrary threshold. But for the JAMA study, researchers included hearing loss down to around zero decibels in their analysis and found that they still predicted correspondingly lower scores on cognitive tests. “It seemed like the relationship starts the moment you have imperfect hearing,” says Justin Golub, the study’s lead author and an ear, nose and throat doctor at the Columbia University Medical Center and NewYork-Presbyterian. Now, he says, the question is: Does hearing loss actually cause the cognitive problems it has been associated with and if so, how?
Preliminary evidence linking dementia and hearing loss was published in 1989 by doctors at the University of Washington, Seattle, who compared 100 patients with Alzheimer’s-like dementia with 100 demographically similar people without it and found that those who had dementia were more likely to have hearing loss, and that the extent of that loss seemed to correspond with the degree of cognitive impairment…
…Hearing loss has also been associated with an atrophy of brain tissue in auditory regions, potentially from lack of use. People who can’t hear well tend to be less likely to go out and engage with others socially too, which is another known risk factor for dementia. It’s possible to imagine any of these processes leading to cognitive decline. “The brain is made up of all these interconnected networks, and if you throw off the balance a little bit over years and years, that may have these widespread effects that are hard to measure clearly,” says Jonathan Peelle, an associate professor of otolaryngology at Washington University, in St. Louis.
…But the JAMA study and others suggest that perhaps we should be working harder to respond to hearing loss earlier. In 2018, Peelle and colleagues published a small study of university students who reported no hearing difficulties. They nonetheless found that those whose hearing was poorer — even within normal levels — had more atypical activity in their frontal cortex when listening to spoken sentences. “Most of the discussion has been around, If you have an older adult with hearing loss and you give them a hearing aid, does that help them?” Peelle says. “What we don’t know is if the whole problem is living for 20 years with a little bit of hearing loss. Maybe we need to be intervening earlier.”