What causes hearing loss and tinnitus?
Well, frankly, too many things to include in this post. For now let’s narrow things down to the most common types of hearing loss and tinnitus in adults and their causes. The most common types of hearing loss are “presbycusis,” otherwise known as age-related sensorineural hearing loss (affecting the inner ear and/or hearing nerve) and noise induced hearing loss (NIHL) which is also sensorineural in nature. The most common tinnitus (perception of a sound that is not coming from the outside world) is constant, high-pitched ringing or static-like sound. This type of tinnitus often occurs in conjunction with the aforementioned types of hearing loss and can be triggered or exacerbated by non-auditory issues like teeth grinding and trauma to the head, neck, or jaw. There is another post to be written about managing tinnitus and all of the mechanisms involved – there is no singular cure but there is a lot more that can be done for tinnitus than most healthcare providers understand. But in order to effectively manage tinnitus, they need to understand the mechanisms of it which a deep topic that I made an entire course on for healthcare providers. Today, I will simply try to address preventing it from getting worse.
We see decline in hearing with age in humans and other mammals. I’d like to note here though, there are no norms for hearing loss with age. In other words the phrase “Your hearing is normal for your age” is usually misleading – your hearing is in the normal range or it isn’t, that has nothing to do with your age if you are an adult.
What is particularly challenging when discussing age-related causes is that we are talking about a wide variety of factors, some of which are more preventable than we think. So, if aging is not preventable but some of the factors associated with age-related hearing loss are, then are we really talking about a wide group of causes that happen to be more common as most people age, instead of just pure aging? All I can say is that the hearing and auditory processing challenges we see with age are influenced by 3 main things; blood-flow, oxidative damage, and brain health. See this fantastic study by Frank Lin, PhD for more information.
The ear is extremely oxygen hungry and sensitive to disruptions in blood-flow.
Any condition that is associated with decreased vascular health (e.g. Diabetes), atherosclerosis, or stroke can thus cause restrictions in blood-flow to the ear and/or hearing nerve and result in hearing loss and/or tinnitus. I have not seen a study on the relationship of treating atherosclerosis and reducing risk of hearing loss, but it makes sense to me that having a healthier heart and blood vessels and reduced risk of blood clots would then reduce risk of this type of hearing loss.
What’s more, blood delivers antioxidants to and clears toxins from every nook and cranny of our bodies. Oxidative stress causes a cascade of degradation (particularly of mitochondria) and cell death in many areas of the auditory system including the tiny sensing hair cells, supporting cells, and blood supply of the inner ear as well as the hearing nerve. Just from the basics I understand from research, antioxidants can create an environment that counteracts this oxidative damage. Our genetics, diet, and lifestyle all have an impact on oxidative stress in our bodies. Furthermore, some research supports that even pre-diabetic blood sugar issues can have a significant impact on these metabolic processes. Here is the wikipedia article on oxidative damage.
Oxidative damage is part of what causes hearing loss from noise exposure. As we get older our cumulative exposure to noise over the years naturally increases – that’s right, the effects of noise are cumulative, you have the same ears that your were born with. Sound is a pressure wave and the sensing cells of the inner ear respond to these pressure waves traveling through the fluid of the inner ear. When there is enough repeated, high level pressure, it can damage these cells. An analogy I find it helpful is thinking about a pathway through a field that has been worn in by many people walking on the grass over and over again, until it wears away to the dirt. If dirt bikes created such a path it would happen much more quickly than just from foot traffic. Damage from noise exposure (foot or motorized traffic in the above example) results from the intensity of the noise and the length of time you are exposed.
Some populations are more likely to have more noise exposure; whether it is related to work in factories, large equipment on farms, use of explosives and guns, or exposure to loud music (to name a few sources) without hearing protection. Some birds and fish are able to regrow the tiny sensing cells in their inner ear after they are damaged; humans, as far as we can tell, do not do this (Dr. Rubel is working on this). Once you damage your hearing from noise, it does not improve. There is a small caveat to this – we can have a temporary (1-2 day) decline in hearing following an exposure to loud noise.
The three main ways to prevent NIHL are to:
1) Turn the volume down.
2) Walk away from loud noise.
3) Wear adequate hearing protection and wear it properly.
How do you know it’s too loud/you should be wearing hearing protection? It’s too loud if: your headphones are in your ears and someone in the room with you can hear your music, you have to shout to someone an arms length away from you in order for them to understand you, or you left an event with your ears ringing.
It should be noted that being exposed to noise while being exposed to other sources of oxidative damage can magnify the effect of both. An example of this is inhalation of organic solvents while being exposed to loud noise. In this situation, part of your hearing protection could be an air filtration system. Here is a Korean study from 2014 about this.
Another cause of damage to the inner ear is ototoxic chemicals.
Ototoxic literally mean toxic to the ear (‘oto’). Make sure to read the list of side effects before taking medications and talk with your doctor about risks like hearing loss and tinnitus before you start taking it and/or immediately after you start to notice a change in your hearing or ringing. Some examples of these ototoxic medications include aminoglycoside antibiotics, platinum based chemotherapeutic agents, and loop diuretics. Individuals who undergo chemotherapy often have regular high-frequency hearing tests (more sensitive to early toxicity to the ear than a regular hearing test) to monitor the effects on their ears.
As I said, this is by no means an exhaustive list of causes of hearing loss and tinnitus. Head injuries, autoimmune conditions, and viral infections are a few more sources of damage to the inner ear and nerve and there are many causes of damage to the outer and middle ear that cause another type of hearing loss. Tinnitus alone can be directly caused or exacerbated by things like jaw position, teeth grinding, and stress. There are still hearing losses in which researchers do not know the cause. Even if you already have sensorineural hearing loss, it is important to prevent further decline. *Wondering what “conductive” and “sensorineural” hearing loss means? Learn more here.
Statistically speaking, it is highly likely we will acquire some kind of hearing loss in our lives. As we age, it is more likely to be a permanent hearing loss. So, do what you can to prevent it, but it is wise to address communication issues and prepare for hearing aids sooner rather than later.
Like I mentioned earlier, we usually isolate discussion to the ear alone when we talk about hearing, but the reality is that we hear the signals from our ears with our brains. Imagine if you had to fly a plane and all of your sensors and equipment worked perfectly (e.g. your ears and eyes), but you couldn’t figure out what most of the dials or controls meant (i.e. processing auditory and visual information). In other words, one could have normal hearing but have auditory processing problems, or for that matter hearing loss and auditory processing problems.
I see how my patients’ processing abilities decline with age, health, and increased stress, effecting their ability to benefit from hearing aids. Interestingly, unaided hearing loss (aka hearing loss one has been putting off getting hearing aids for) has a strong correlation with decreased brain volume, increased risk of fall, and depression – even when researchers corrected the results for age! There will have to be an entire post on the effect of brain health on hearing and the effect of hearing loss on the brain!
1) Protect your hearing from loud noise. Here is an option that is great for concerts and noisy bars – Westone TRU. I recommend disposable foam plugs, over the ear muff style protection, or custom made earplugs for occupational noise. Just make sure you are wearing them properly, for example plugs in deep enough and avoid wearing glasses that pop muffs out and break acoustic seal.
2) Maintain good cardiovascular and digestive health (for absorption of essential nutrients, gut health, and optimal blood sugar health). *My recommendations in this area are based on my personal review of nutrition literature and not from studies that show direct correlation to ear health. Additionally, my views often do not agree with the traditional approach to health and wellness.
3) Be aware of the side effects of your medications and chemicals in your environment.
4) Any sudden change in hearing or ringing in your ear(s) warrants immediate medical attention. I recommend seeing an Ear, Nose and Throat physician. Any progressive decline in hearing or increase in tinnitus warrants evaluation of the ears and a hearing test.
5) Hearing tests don’t hurt. Even if you don’t have current hearing concerns, a baseline hearing test can be extremely valuable. Most insurance will cover at least one hearing test a year – make sure it is administered by an audiologist. A hearing test every decade until age 50 and then every 3 years is recommended unless a doctor recommends more often for you.