Hearing loss related to the ageing process (presbycusis) affects 1 in 3 over 65's and has certain common characteristics. It tends to be very gradual, and the higher frequencies suffer earliest and worst.
While you may start to lose the upper frequencies (pitches) after 55, it is usually much later that the person notices they're not hearing well. Since not hearing 100% of words is pretty normal, it takes a while to catch on that what you're experiencing is not normal. You may be struggling more than your friends, say, when in a cafe or restaurant. You may have a spouse who is getting frustrated that the TV is on a few notches higher than they like it. At this point you probably have a moderate, high frequency hearing loss that's been developing for years.
Hearing loss is auditory deprivation. The ears channel sound to each cochlea (the organ of the inner ear), via the eardrum and middle ear bones. The cochleae transform those movements caused by sound into electrical signals that your brain can interpret.
We have an auditory cortex on each side of our brain, which processes these sound signals, discriminates between frequencies, compares the time differences between the two ears. Our brains take the masses of overlapping sounds from two ears, then combine this data use our working memory, language processing, our short and long term memory to make sense of what we are hearing. It's one of those everyday miracles that you don't think about! You hear a mass of sound in the café, and you process it in fractions of seconds, separating out the coffee machine and clattering of cups and spoons. Your friend is saying "Bob's daughter is home from uni so he can't make it to bowling, can you make it on Thursday instead? Lovely girl, what was her name again?" You're processing those sound vibrations, picking out the language elements, holding it in your working memory (so you don't lose track of the beginning of the sentence while the rest of the words arrive). You're taking in visual information too - the shape of the lips and the changes in facial expressions are important factors in speech processing. You're hearing a name, which is attached to your memory of Bob so you know who's being discussed. You're remembering that you have bowling in your diary and realising you're being asked to change you're schedule. You're (almost) immediately thinking about what plans you have on Thursday. You're also about to dip into your long term memory to find the name of Bob's daughter.
An absolute miracle, and we do it all day every day.
So, although the auditory cortexes are responsible for processing sound, we are using other higher functions whenever we hear speech. Mapping the "shape" of the sound and comparing it to our memory bank of words. Using our ability to reason and plan, coming up with a response even while the other person is still talking, filtering out unwanted noise while still being aware of it. Working memory, which degrades as we age, is crucial to language, so the auditory cortex is definitely not the only star of the show when we have a conversation. Working memory has to work a lot harder when you have hearing loss, because it's trying to fill in the gaps and compare the options. Was it "two" or "three"? "fee" or "see" (or "sea" even)? Multiply this work by hundreds of occurrences in even a short conversation, and you will see why hard of hearing people are shattered after a conversation!
Our ears are crucial parts, but we hear in our brain, and the higher functions of the brain are reliant on being fed with sound to strengthen connections and retain their skill sharpness. When we have hearing loss we deprive our brains of sound, and much research (e.g. Davidson et al, 2019) has shown that this deprivation affects the efficiency of our verbal working memory and reasoning ability.
The stage at which you decide to take up wearing hearing aids has an impact on how you will fare in later life. Audiologists have known for many years that it's not always possible to get a deprived ear (auditory cortex) working again with a hearing aid. This often presents itself as a problem when a patient has one ear worse than the other. So far, they've got by relying on their better ear, but when they get to 65 they then get presbycusis. Now their good ear is getting bad, the bad ear is getting even worse and they need hearing aids! But it's not as simple as finally getting the aids, because that bad ear's auditory cortex has been deprived of sound for a long time, and the new sound coming into it is not processed effectively. This results in "blurry" hearing on that side, and when you combine the two sets of data the overall effect is poor hearing. After trying to rehabilitate the poorer ear, the patient, audiologist or both may conclude it's better to stick with just one aid. An ageing brain is harder to rehabilitate than a younger one, so your chances of hearing well again with a 10-year unaided loss will be lower if you're 75 than if you're 45. Your audiologist might not attempt it, knowing the outcomes are shaky (although I will always attempt it, unless the patient doesn't want to, because two ears are helpful for so many reasons).
The majority of hard of hearing people in later life have presbycusis - they have two ears declining at the same rate. We already knew that the longer you leave it to get hearing aids, the worse the outcome is likely to be. You'll still struggle to pick out speech in background noise, even with the best pair of aids you can buy. But now we have extensive research that shows what is happening when you ignore presbycusis and delay wearing aids, which millions of people are currently doing.
Working memory speed and ability declines as we get older. Understanding speech requires working memory among other things. Having hearing loss impairs your working memory, and untreated hearing loss can permanently damage it, making it decline faster. The flip side of this is the positive news that mild cognitive impairment (MCI) caused by hearing loss can be eliminated by wearing hearing aids. A 2022 study found there was no significant difference in risk of MCI between normal hearing people and people who wore hearing aids to compensate for their hearing loss.
Untreated hearing loss damages your ability to distinguish between different frequencies, which is important for understanding speech, particularly in noise. It has also been linked to a decrease in brain volume (atrophy). There are proven, strong links with dementia and cognitive impairment, such that if hearing loss vanished from the world, approximately 9% fewer people would get dementia in later life.
These midlife hearing changes affect not only hearing but your wider brain function in later life, and we are just starting to realise the vast implications for people. With eyesight, you buy a pair of glasses and they can pretty much put you right. You can see clearly again. With hearing loss, you get the hearing aids but they don't restore hearing ability completely. Not only that, but if you waited and waited before aiding the loss, you're not doing the Times cryptic crossword anymore because it's become frustrating. You're not reading novels anymore, only non-fiction. You're not enjoying the cinema anymore because it's difficult for you to follow which character is which and why they're important. When we say "cognitive impairment", it can be difficult to work out what that looks like in real life, but if you've suffered from ' baby brain' or the brain fog that comes with COVID 19 (or even a hangover) you can perhaps imagine it.
I see some scenarios relatively often, with my middle aged patients. They have a first hearing test because their spouse insisted they get one. The graph shows a moderate, high-frequency hearing loss but they tell me they can "still hear", which of course they can. People expect hearing loss to sound different, but what a high-frequency loss sounds like is 'dull'. Things aren't as sharp or clear, and it's been happening so gradually they've got used to it. They're not aware of people around them in supermarkets, they're in a kind of dull bubble. They struggle to hear friends in a restaurant, but because they only do that once every couple of months it's not much of an issue for them, so wearing hearing aids every day seems like overkill. They'll put off tackling it for another five or seven years even though the spouse is driven crazy by them not responding when they're spoken to from behind, or the spouse notices that they're not responding in a group conversation.
At the other end of the timescale, I will fit a 75 year old patient with their first pair of aids - a fabulous and rather expensive pair of hearing aids. We'll fine tune them, we'll do our follow ups and they'll tell me "I don't understand. My friend has hearing aids and when we meet up for lunch she can hear much better than I can. She's on her second pair and I'm sure she's no better than I am on her hearing test ." They will ask if I'm sure I've chosen the right pair, they might be dubious why I was recommended to them by the friend who's hearing so well, when I clearly can't get their aids working right!
"Your mileage may vary" is a phrase that's so relevant with hearing aids, and delaying the inevitable is the main reason why two people with very similar audiograms (hearing test results) can find the experience of hearing in background noise so different. Technology is amazing now, truly amazing, but we are only scratching the surface of how important hearing and hearing loss is to people. Who among us knew, 30 years ago, the long-term implications of hearing loss on your cognitive ability or the other things that seem so unrelated?
I am clear that I don't try to push people into getting hearing aids before they are ready to wear them. I don't want to risk people having a negative experience with me that turns them off revisiting a hearing test in the future. I do ask them if they want to know what the benefits are, beyond not missing the phone ringing and hearing the birdsong again. But it is complex, and people are often unsure of the connection between being able to hear well and the far reaching, long term effects on their brain health. Because it increases their risk factor for dementia/cognitive decline/working memory/speech discrimination/frequency discrimination, but it is not guaranteed that it will happen to them, they can easily put it out of their minds.
It occurs to me that I do exactly the same thing when the doctor or nurse gently prods me about my BMI, alcohol units or smoking (I quit six months ago!). I find it difficult to equate today's burger with tomorrow's stroke or the restrictions of diabetes. Hearing aids are easier to promote, because there are immediate pleasures such as rich music, easy conversation and fewer aggravations from the spouse. However, it's the 10% of people who are resistant to even free NHS aids that are the ones I need to communicate with. Advise without scaring them off, help remove barriers to using aids by making them comfortable and easy to use. Beyond the percentage of people in my clinic who are resistant to wearing aids are the ones who won't set foot in the clinic in the first place, and they need to be communicated with too, somehow.
So, if you're wearing hearing aids every day, do be pleased that you're protecting your brain in so many different ways. But also, be an ambassador for hearing aids. Try not to grumble about them, be positive in the company of friends who are putting off getting them. Tell them it's great not to struggle in conversations, tell them how you never realised until you got the hearing aids how much you'd been missing out. Tell them it's not as bad having to wear them as you first thought! Audiologists can't work their magic until the person takes the first step, but you can be a positive influence to those reluctant loved ones.