Hearing Loss and Declining Brain Function

Hearing Loss and Declining Brain Function

Amazingly, the first report on the relationship between hearing loss and decline in brain function appeared about 30 years ago (thank you Richard Uhlmann, Eric B Larson et al. - link at the end). Today we know a great deal more about the link between sensory stimulation of the brain and keeping cognitively sharp but, while a full understanding may still be decades away there are things we can do today in order to live healthier for longer.

The first issue to address is that what we already DO know about the link between hearing and cognition simply doesn't filter through to those people who could already benefit from this knowledge today. From my perspective there are two key groups here, those who are losing their hearing through the process of ageing and those who are losing their hearing through exposure to loud sounds. The evidence appears simple and obvious: for the first group there is typically a 10 year gap between when a person would benefit from a hearing aid and when they eventually get one. This means 10 extra and unnecessary years of reduced brain stimulation. For the second group, there is a systemic lack of care when it comes to protecting hearing from loud sounds as evidenced by the sheer volume of clinical cases presenting for Noise Induced Hearing Loss and Tinnitus in Audiology clinics across the country.

The Baltimore Longitudinal Study of Ageing was started in 1958 by the National Institute on Ageing to track various health factors in thousands of men and women. One of the most compelling findings from this study is that those with hearing loss lose more than an additional cubic centimetre of brain tissue each year compared with those with normal hearing. It goes without saying that losing brain tissue at accelerated rates will lead to a deterioration in a person’s cognitive ability and cognitive decline is bad for everyone. If we then consider the size of our ageing population, we’ve got a serious problem on our hands. (Thank you Frank Lin et al. for your amazing work - link at the end.)

This means the silent epidemic of hearing loss should be a matter of public health urgency.

Imagine if there was a way to prevent hearing loss in the first place.

Slowing or even reversing the ageing process is a lofty goal but that hasn’t stopped Nikolay Kandul repairing ageing cells, Geraldine Gontier switching old blood for new and David Sinclair enhancing cellular ageing regulation, amongst countless others, from trying. Not to forget (could I?) Calico, Human longevity and Elysium who may well between them be trying out every possible method of controlling ageing.

There are plenty of risks to think about when considering the science of controlling ageing and its link to the rest of the world. A great example is the ‘brain-training’ company Lumosity (Lumos Labs). Based in San Francisco, Lumosity has had 70 million people over the past decade play games that the company claimed could “ward off cognitive decline.” These claims resulted in The Federal Trade Commission handing Lumosity a $2 million fine based on their adverts being unsubstantiated.

From my experience, I bet it will be the business and commercial world working hand-in-hand with academic institutions adopting an evidence-based approach, governed by market forces, that will bring innovation to those who will benefit most. Of the two groups most in need that I referenced above, I’m focused on the second group: those who are losing their hearing due to noise exposure and within that group, those losing their hearing due to occupational noise exposure. I’ve spoken with thousands of people in the UK and Europe who work in noisy industries like construction, manufacturing and engineering. Almost all of them will talk about having a ringing in their ears or hearing loss. What’s most distressing is that most of them describe it as if it’s a normal state.

Noise induced hearing loss claims are in the order of £400m per year in the UK alone. A volume like that suggests thousands of people are suffering from hearing damage, most of which could be avoided by changing the way risk is managed, mitigated, educated and by design and distribution of proper noise control measures and protection.

The main reason I’m spending my time on Occupational Noise Induced Hearing Loss is that I believe in the powers of root cause analysis, prevention and taking the shortest road.

Thinking back to Frank Lin's study, those with hearing loss had accelerated rates of brain atrophy compared to those with normal hearing and significantly more brain shrinkage in particular regions responsible for processing sound and speech (probably due to lack of stimulation). The issue with this is that each region of the brain does not work in isolation. The connections in the brain are like an unimaginably complex three-dimensional spider web. The brain contains around 100 trillion neural connections between the various regions and are by their very nature not working in isolation, including those responsible for processing sound and language. It’s this interconnectivity that can give rise to fascinating human conditions like Synesthesia and that allows us, through neural plasticity, to develop our expertise both physically (motor skills) and intellectually (learning and experience.) Unfortunately, we also know that this interconnectivity and the decline in areas processing memory and sensory integration are involved in the early stages of mild cognitive impairment and Alzheimer’s disease.

So what to do? Thankfully, knowing a problem means you are well on your way to solving it. This concluding section could well be multiple articles in itself so if there is interest, I'm willing. Until then and first of all, take care of your own hearing - don’t over-expose yourself to noise and if you or those around you think you might have a hearing loss, get it checked out and addressed as soon as possible. Second, think of Future-You and live healthily today - exercise, socialise, sleep, be present, eat well and smile often. Third, if you are responsible for other people’s hearing, perhaps as a health and safety specialist, occupational hygienist or responsible manager in an industry that produces workplace noise over 80dB it, directly address your risks immediately. It is your legal and dare I say moral obligation. The risk-debt that is building up by ignoring or not understanding today’s occupational noise problem will be something we will all pay for later. For all of these, but especially the third, get in contact with me and the team at EAVE to see if we can help.

N.B. I’ve left out a number of references from this article to keep it brief so feel free to contact me if you would like links. Sorry and thank you to everyone working in the space for not covering this as extensively as it deserves. I wish I could include it all as there is plenty more to say. Please reach out if there’s anything further you’d like to discuss.

References:

Richard Uhlmann, Eric B Larson et al. 1989

https://jamanetwork.com/journals/jama/article-abstract/376858

Frank Lin et al. 2014

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3951583/

London Underground Noise Levels Revealed

London Underground Noise Levels Revealed