Hearing loss is simply what happens when sound from the world around us isn’t communicated to the brain properly, for whatever reason. It can affect you in many different ways, but it can also be a difficult condition to navigate for your friends and family.
Understanding the causes of hearing loss can help you and your loved ones understand the condition.
Types of hearing loss
To understand what might be causing your symptoms, it is important to first understand the different types of hearing loss.
There are two main types of hearing loss: sensorineural hearing loss and conductive hearing loss.
Sensorineural hearing loss occurs due to abnormalities in the neural pathway that carries sound information to the brain (including the inner ear and auditory nerve), while conductive hearing loss is caused by soundwaves being blocked from passing through to the inner ear. This is usually due to blockages in the ear canal.
It is possible to have both types of hearing loss at the same time. This is known as mixed hearing loss.
Each type of hearing loss can be brought on by different factors.
What is the biggest cause of hearing loss?
Becoming hard of hearing is commonly associated with age, and this type of hearing loss — known as presbycusis — is the most common cause of hearing impairment. Presbycusis is a sensorineural type of hearing loss and occurs due to gradual damage to our ‘hearing cells’ over time.
These cells are tiny hairs in our inner ear that detect vibrations in the air (i.e. sound) that simply become worn out as we age. Usually, this type of hearing loss is initially quite mild, but can progress to being moderate and severe as we get older.
Presbycusis typically affects both ears equally, and those who have it often report that they find it more difficult to follow conversations, as higher pitches and tones become harder to hear. Soft sounds, such as ‘s’, ‘th’ and ‘f’ can also get lost in background noise.
Hearing aids are usually recommended for age-associated hearing loss, and many who use them report improvements both to their hearing and quality of life.
Can COVID-19 cause hearing loss?
Current research shows that most people who contract COVID-19 do not experience hearing loss as a symptom. However, there is some evidence to suggest that COVID-19 can cause hearing loss in rare cases.5,7
Recent research looked into the link between COVID-19 and audio-vestibular symptoms across 24 studies.5 Scientists found that in people who were infected by COVID-19, 7.6% experienced hearing loss, 14.8% experienced tinnitus (ringing in the ears) and 7.2% experienced rotatory vertigo (feelings of spinning and dizziness).⁸
The WHO has now also linked ‘hearing issues’ to long Covid, identifying it as a symptom in their recent definition of the post-COVID-19 condition.6 In some rare cases then, coronavirus can be known to impact your hearing, as well as your balance.
Can high blood pressure affect your ears?
Hypertension can accelerate the ‘wear and tear’ of the auditory system in your ears. Research has shown that long-term hypertension is also linked with fatty plaque build-up in your blood vessels, depriving your ear and internal structures of much-needed blood and nutrients.
The end result is that high blood pressure over both the short and long term can have a noticeable effect on your hearing.
The current theory is that very high blood pressure can permanently damage the tiny blood vessels in your ears, reducing your ability to hear the full spectrum of sound.
Common causes of mixed hearing loss
A mixed hearing loss refers to the experience of having both sensorineural (affecting the inner ear) and conductive (affecting the middle and outer ear) hearing loss at the same time. This can lead to more severe hearing loss than if you were affected by one type alone.
Mixed hearing loss often has more than one cause but can also occur when one factor affects the ear in different ways. For example, if you had a long-standing infection, then you might experience conductive hearing loss due to physical blockage. You might experience this alongside eventual sensorineural deafness as the infection affects the hair and nerve cells of the inner ear.
To prevent mixed hearing loss, it’s important to address the root causes of both the sensorineural and conductive hearing loss you are experiencing.
Diabetes and hearing loss
The effect that diabetes can have on your blood vessels and nerves can cause issues with your ears, sometimes causing an ‘injury’ to the inner ear which can affect your hearing.⁹,¹⁰ Unstable blood glucose levels can also put you at greater risk of hearing loss.¹²
While it’s unclear exactly what happens, scientists have found that high blood sugar levels can damage the small blood vessels in the inner ear, affecting blood circulation in that part of your ear.¹¹ Your hearing can also be affected if you have low blood sugar.¹⁵
Research has found that this is because low blood sugar is one of the factors that can create a chemical imbalance in the fluid found in your ear.¹⁶,¹⁷ This fluid has a very specific make-up which allows the cochlea to function properly, so if this is altered it can change the way your ear processes sounds.
If you have diabetes you may start to notice subtle changes to your hearing, particularly with high-frequency sounds.¹³,¹4 For example, you may find vowel sounds easy to identify, but the letters f, s, t and z, may be more difficult for you to notice. Or sounds with higher octaves, like birdsong, may not be as clear.
People with diabetes have an increased risk of infection and related complications. One type of common ear infection is malignant otitis externa, which only affects diabetic people.
This is an infection of the external ear canal and skull base, which usually affects older people with diabetes.¹⁸ The infection is caused by bacteria and can spread to surrounding areas (like the jawbones or face) if it’s left untreated.¹⁹
Sudden hearing loss can be a symptom of this infection, so you should get your ears checked out quickly if you are diabetic and experience sudden hearing loss. Diabetic people can also be at a higher risk of developing inner ear infections due to excess insulin.²⁰ So controlling your insulin levels and having regular check-ups are important to avoid both of these types of infection.²¹,²²
If you have diabetes you may experience hearing loss to some extent, but maintaining stable blood sugar levels should help you reduce the impact of your diabetes on your hearing. It’s also important to seek early treatment for injury and infection, protect your ears from prolonged exposure to high noise levels and quit smoking as it can increase the risk of hearing loss.²¹
- HSE, ‘Noise induced hearing loss in Great Britain’, Health and Safety Executive, no date, [online], https://www.hse.gov.uk/statist... (accessed 16 July 2020)
- Bisht M, & Bist S.S., Ototoxicity: the hidden menace, Indian J Otolaryngol, Head Neck Surg. 2011;63(3):255-9
- Shearer A.E., Hildebrand M.S., Smith R.J.H., ‘Hereditary Hearing Loss and Deafness Overview’, in Adam M.P., Ardinger H.H., Pagon R.A., et al (ed), GeneReviews [internet], Seattle (WA): University of Washington, Seattle; 14 Feb 1999 [updated 27 July 2017], https://www.ncbi.nlm.nih.gov/b... (accessed 16 July 2020)
- Le saux N, Robinson J.L., Management of acute otitis media in children six months of age and older, Paediatr Child Health, 2016;21(1):39-50.