Jane E Brody
CNA/THE NEW YORK TIMES – Every now and then I write a column as much to push myself to act as to inform and motivate my readers. What follows is a prime example.
Last year in a column entitled ‘Hearing loss threatens mind, life and limb’, I summarised the current state of knowledge about the myriad health-damaging effects linked to untreated hearing loss, a problem that afflicts nearly 38 million Americans and, according to two huge recent studies, increases the risk of dementia, depression, falls and even cardiovascular diseases.
Knowing that my own hearing leaves something to be desired, the research I did for that column motivated me to get a proper audiology exam.
The results indicated that a well-fitted hearing aid could help me hear significantly better in the movies, theatres, restaurants, social gatherings, lecture halls, even in the locker room where the noise of hair dryers, hand dryers and swimsuit wringers often challenges my ability to converse with my soft-spoken friends.
That was six months ago, and I’ve yet to go back to get that recommended hearing aid.
Now, though, I have a new source of motivation. A large study has documented that even among people with so-called normal hearing, those with only slightly poorer hearing than perfect can experience cognitive deficits.
That means a diminished ability to get top scores on standardised tests of brain function, like matching numbers with symbols within a specified time period.
But while you may never need or want to do that, you most likely do want to maximise and maintain cognitive function: Your ability to think clearly, plan rationally and remember accurately, especially as you get older.
While under normal circumstances, cognitive losses occur gradually as people age, the wisest course may well be to minimise and delay them as long as possible and in doing so, reduce the risk of dementia.
Hearing loss is now known to be the largest modifiable risk factor for developing dementia, exceeding that of smoking, high blood pressure, lack of exercise and social isolation, according to an international analysis published in The Lancet in 2017.
The analysis indicated that preventing or treating hearing loss in midlife has the potential to diminish the incidence of dementia by nine per cent.
Difficulty hearing can impair brain function by keeping people socially isolated and inadequately stimulated by aural input.
The harder it is for the brain to process sound, the more it has to work to understand what it hears, depleting its ability to perform other cognitive tasks.
Memory is adversely affected as well. Information that is not heard clearly impairs the brain’s ability to remember it. An inadequately stimulated brain tends to atrophy.
The National Institute on Aging is currently sponsoring a trial of 997 people aged 70 to 84 with mild to moderate hearing loss to determine how effective hearing aids can be in diminishing the risk of dementia.
Results of the trial, called Ageing and Cognitive Health Evaluation in Elders, are expected in 2022.
Meanwhile, the new findings on cognitive losses linked to subclinical hearing loss, gleaned from among 6,451 people age 50 or older, suggest that any degree of hearing loss can take a toll.
Currently, the sound level of 25 decibels – the ability to hear a whisper – is used to define the border between normal hearing and mild hearing loss in adults.
But this threshold is really arbitrary. The lead author of the study, Dr Justin S Golub, otolaryngologist and researcher at Columbia University Irving Medical Center, and his colleagues found that hearing loss is on a continuum that starts with “perfect” hearing at zero decibels (the sound level of a pin drop), with measurable cognitive deficits occurring with every additional loss above zero.
In fact, the researchers demonstrated that the biggest drop in cognitive ability occurs at the slightest level of hearing loss – a decline from zero to the “normal” level of 25 decibels, with smaller cognitive losses occurring when hearing deficits rise from 25 to 50 decibels.
“This doesn’t mean we should be fitting people with hearing aids when the softest sound they can hear is 25 decibels,” Golub said in an interview. After all, getting people with far more advanced hearing loss to use hearing aids is already an enormous challenge.
As Golub noted, “Currently only 25 per cent of people over 80 wear hearing aids, yet 80 per cent of them have significant hearing loss” that might be greatly improved with aids.
The new findings linking cognitive decline to even minimal hearing loss suggest that we could do a lot to protect our brains if we protect our hearing.
The fact that measurable cognitive losses occur at hearing levels below 25 decibels, and that cognition gradually worsens as hearing declines, suggests that protecting against hearing loss should start in childhood.
“In people with very good hearing, we need to be aware of how early changes in hearing affect the brain,” said Director Dr Frank Lin at the Cochlear Centre for Hearing and Public Health at the Johns Hopkins Bloomberg School of Public Health. “Without a doubt, the most important measure to preserve hearing is protection against noise.”
The two characteristics of noise associated with the greatest damage to hearing are intensity – that is, loudness – and duration, or how long unprotected ears are exposed to very loud sound, Lin explained in an interview.
“The damaging effect of noise exposure is cumulative,” he said. While he is less concerned about ear protection during the relatively brief time someone uses a hair dryer or stands on a New York City platform as a train screeches into the station, people who work all day in the subway or listen to loud music for hours need to protect their hearing.
“We can see a hearing deficit the next day after someone has attended a very loud concert,” Lin said.
He urges people who listen to music through headphones or earbuds to invest in ones with a noise-cancelling feature that blocks ambient sound.
This enables people to listen to their preferred music or programmes at a lower volume that is less damaging to hearing.
Apple, for example, now markets AirPods Pro earbuds that have a noise cancellation feature. At USD249 a pair, they are a lot cheaper than currently available hearing aids.
That said, by 2021, a selection of much less expensive over-the-counter hearing aids is expected to be on the market.