The World Health Organization predicts that by 2030 one in four people globally will have some degree of hearing loss. That’s 2.5 billion people worldwide. If we want to prevent hearing loss, we need to understand the causes.
This guide will explore the underlying causes of hearing loss and why cases are on the rise.
Causes of Hearing Loss
Hearing loss is most commonly caused by damage or degradation of the ear due to age or noise. Other causes include:
- Infections
- Genetic disorders
- Toxic reactions to medications and chemicals
- Chronic health problems like diabetes and cardiovascular disease
- Autoimmune conditions
Types of Hearing Loss
To better understand root causes, we should briefly go over the main types of hearing loss.
Hearing loss is classified broadly into two categories—sensorineural and conductive—defined by the area of the ear affected:
- Sensorineural hearing loss is caused by damage to the auditory nerve or inner ear structures like the cochlea. With a few exceptions, sensorineural hearing loss is generally permanent and irreversible.
- Conductive hearing loss occurs in the middle or outer ear. Sound is disrupted on its way to the inner ear by a defect or blockage. Many typical varieties of conductive hearing loss can be reversed through medical treatment or surgery.
When a person is experiencing both types simultaneously, that’s called mixed hearing loss.
Causes of Sensorineural Hearing Loss
While any trauma or medical condition that affects the nerves or structures of the inner ear can cause sensorineural hearing loss, the two primary culprits are age and loud noise.
Age-Related Hearing Loss
As a person gets older, the cochlea, semicircular canals and other components of the inner ear start to break down.
Degradation of the nerve pathways connecting the inner ear to the brain may also play a role. The medical term for age-related hearing loss is presbycusis.
Although it’s more common in adults over 60, some begin experiencing age-related hearing loss as early as their late 30s.
Half of people older than 80 have age-related hearing loss.
People with this form of hearing loss lose their ability to hear sounds at the higher end of the spectrum, making it difficult to understand conversations. Age-related hearing loss is progressive and irreversible, but it can be managed and treated with hearing aids.
Noise-Induced Hearing Loss
Noise exposure accounts for an alarmingly high number of sensorineural hearing loss cases. Loud noises in excess of 85 decibels damage the tiny hair cells inside the inner ear that capture sound waves, causing permanent hearing loss.
This form of hearing impairment is more common in occupations where people are regularly around loud noise, such as construction, manufacturing and the military. Unsafe listening practices are also increasingly to blame.
Health experts warn that one in five teenagers are now at risk of hearing loss because they listen to loud music on headphones for extended periods.
Noise-induced hearing loss is irreversible but generally treatable with hearing aids and preventable. Limit noise exposure using hearing protection and restricting the volume of personal devices.
Genetic Disorders
Though they are less common, genetic disorders can cause the malformation of hair cells in the inner ear or affect the auditory nerve, causing genetic hearing loss. Some genetic disorders cause hearing loss from birth, while the onset for others is delayed or progressive.
Some genetic disorders that can cause sensorineural hearing impairments:
- Waardenburg syndrome
- Usher syndrome
- Pendred syndrome
Cardiovascular Conditions
Sudden sensorineural hearing loss can occur when there is an interruption or reduction in the flow of blood to the arteries that supply the nerve cells responsible for hearing or the brain’s auditory cortex.
Examples include:
- Stroke
- High blood pressure
- Peripheral artery disease
These are potentially life-threatening conditions, so sudden hearing loss in both ears should be treated as a medical emergency. Seek immediate medical attention if you develop hearing loss suddenly.
Serious Infections
Viral infections can invade the inner ear and attack the cochlea, causing hearing loss. Viruses like rubella are the most common non-genetic cause of congenital hearing loss and deafness in newborns and small children.
Viruses can also cause impairment in adults with normal hearing, especially if they are immunocompromised.
Some viruses that may cause sensorineural hearing loss include:
- Mumps
- West Nile virus
- HIV
- CMV
- Rubeola
Trauma
Head trauma that impacts the auditory cortex can also affect how sound is processed, leading to hearing impairment. Pilots and divers can also suffer damage to the inner ear caused by sudden changes in pressure. This can lead to hearing loss, vertigo, tinnitus and partial facial paralysis.
Chronic Conditions
Some chronic conditions may cause hearing loss. For example, diabetic people experience hearing loss at a significantly higher rate than those without the condition.
Poorly regulated blood sugar affects the ability of nerve cells to transmit electrical signals from your inner ear to the brain.
Disorders like multiple sclerosis can degrade the auditory nerve connecting the inner ear to the brain, causing hearing loss in rare cases. Other conditions like depression and Alzheimer’s also have an association with hearing loss, but the causal relationship isn’t fully understood.
Substances That Harm the Ear
Some substances cause toxic reactions in the ear that can produce temporary hearing loss or contribute to permanent hearing damage when you’re exposed to them for prolonged periods.
More than 700 medications are potentially harmful to the ear, including many over-the-counter pain relievers and anti-inflammatories, as well as some drugs in the following categories:
- Antimalarials
- Diuretics
- Anti-cancer
Chemicals commonly used in construction, home improvement and various occupations can hurt the ear, such as:
- Printing inks
- Polishes
- Paints
- Cleaning solvents
Autoimmune Conditions
A highly rare condition can cause the body’s immune response to attack the ear by mistake. It’s called autoimmune ear disorder, and it affects about 15 out of 100,000 people. It impacts both ears and progressively worsens over a period of weeks to a few months.
Autoimmune ear disorder is primarily caused by systemic inflammatory disorders, such as:
- Scleroderma
- Wegener’s
- SLE
Autoimmune conditions can be treated with steroids.
Causes of Conductive Hearing Loss
Sensorineural and conductive hearing loss involve different parts of the ear, so the causes vary. Anything that interferes as sound waves pass from the outer ear to the middle ear can cause conductive hearing loss.
This includes blockages due to fluid or a foreign object as well as defects or damage to outer or middle ear structures, such as:
- External ear
- Ear canal
- Eardrum
- Middle-ear bones
Middle Ear Infections
Fluid can accumulate throughout the middle ear when you have an ear infection. Your body’s immune system responds by producing large amounts of fluids, potentially clogging the eustachian tube connecting your middle ear to the back of your throat. The eustachian tube can no longer do its job, i.e., draining fluid from the middle ear.
This fluid buildup can block or inhibit sound waves passing through the middle ear, causing temporary conductive hearing loss. While excess fluid can be drained, recurring ear infections might do severe damage to the eardrum that can only be repaired via surgery.
Middle ear infections must be treated promptly, so if you’re showing symptoms of an ear infection, call your doctor immediately.
Blockages
One of the most common types of conductive hearing loss is a blockage caused by excess earwax in the ear canal. Most people have experienced this at least once in their lives. It usually occurs in only one ear, and it’s seldom serious.
The body has a natural mechanism for getting rid of the wax, but some people are prone to earwax buildup to genetics, environment or lifestyle factors like the frequent use of hearing aids or earbuds.
Some folks may also inadvertently cause an impaction by using cotton swabs to clean their ears, further pushing the wax down the ear canal.
An impaction can usually be treated at home by using medicated drops and rinsing the ear canal with warm water. In stubborn cases, you may need a doctor to extract the impaction using suction.
Another type of hearing loss occurs when a foreign object gets lodged in the ear canal. This is most common in small children, but adults sometimes get bugs or bits of cotton stuck in their ears, too. Though it’s somewhat rare, benign growths can also cause blockages.
Middle Ear Bone Pathologies
The middle ear contains three tiny bones called the auditory ossicles that work with your eardrum to transfer sound vibrations to the fluid of the inner ear, where they can be detected by the tiny hairs inside.
These tiny bones are delicate and susceptible to various conditions that can cause conductive hearing loss. One example is otosclerosis, where the bones of the middle ear harden and don’t vibrate like they should.
Defects and Damage
The parts of the middle and outer ear can become damaged or warped by genetic and degenerative conditions.
An eardrum can easily be ruptured by changes in pressure or getting poked by a cotton swab jammed too deep in the ear canal. The blast from an explosion might cause permanent hearing loss by directly damaging the eardrum and the external ear.
While congenital disabilities are seldom the cause of conductive hearing impairment, some people are born with middle or outer ear deformities that affect hearing.
Conclusion
Now that you know the most common causes of hearing loss, you should have some ideas about the best ways to prevent it. While some forms of hearing loss are sadly unavoidable, you can significantly reduce your risk by limiting loud noise exposure. If you work in a job where you’re around lots of loud sounds, invest in hearing protection.
The best defense against hearing loss is early detection. Get regular hearing tests every three to five years, even if you’re young and have normal hearing. Take an annual hearing test if you’re over 50 or work around loud noises. Seek hearing loss treatment as soon as you notice hearing problems. If you have mild or moderate hearing loss, you might invest in a hearing aid.
Citations
2. Lin J, Huang H, Lv G, et al. Chronic prenatal hypoxia impairs cochlear development, a mechanism involving connexin26 expression and promoter methylation. Int J Mol Med. 2018;41(2):852-858. doi:10.3892/ijmm.2017.3303
3. Richardson MP, Reid A, Tarlow MJ, et alHearing loss during bacterial meningitisArchives of Disease in Childhood 1997;76:134-138.
4. Cohen BE, Durstenfeld A, Roehm PC. Viral causes of hearing loss: a review for hearing health professionals. Trends Hear. 2014;18:2331216514541361. Published 2014 Jul 29. doi:10.1177/2331216514541361
