About 466 million people in the world have hearing loss. How does this happen?
Hearing loss occurs when damage is done to the nerves coming from the ears. This can occur in one or more parts of the ear or the brain segment responsible for hearing.
Hearing loss affects people of all ages and can occur from birth or develop later in life.
What Is Hearing Loss?
Hearing loss, also known as hearing impairment or deafness, is the total or partial inability to listen to sounds. Hearing loss may be temporary or permanent, with mild, moderate, severe, or profound symptoms.
People with mild hearing loss often have difficulty understanding speech when there is a lot of noise, and those with moderate hearing loss need to use hearing aids to understand speech.
People with severe hearing loss may need to rely on lip-reading when communicating. In contrast, those with profound hearing loss can’t hear anything and heavily depend on sign language and lip-reading for communication.
Hearing loss can affect one or both ears. The effect of hearing loss isn't restricted to your ability to hear; instead, it can affect the ability to acquire spoken language in children and difficulties with communication and social interactions.
Types of Hearing Loss
As stated above, hearing loss can vary in intensity and be temporary or permanent depending on the cause.
Below are the types of hearing loss.
1. Sensorineural Hearing Loss
This hearing loss occurs due to damage to the sensory hair cells in the cochlea or inner ear. This damage affects the transmission of impulses along the hearing nerve.
People with sensorineural hearing loss have decreased sensitivity to sound. The sound’s clarity is also affected because of damage to the auditory nerve. Even when the sound getting to the inner ear is loud enough, the brain won't receive the signals.
Sensorineural hearing loss can be caused by exposure to noise, anatomical abnormalities of the cochlea, head injuries, measles, prolonged high fever, meningitis, mumps, or hereditary factors.
There is no known cure for sensorineural hearing loss.
2. Conductive Hearing Loss
Conductive hearing loss is caused by an abnormality in the outer and middle ear. The inner ear functions okay, but the sound is attenuated before it gets there.
Abnormal bones can cause conductive hearing loss in the middle ear, holes in the eardrum, rupture of the eardrum, extreme wax buildup and fluid accumulation in the middle ear, and small or absent pinnas.
Conductive hearing loss can be corrected with medication or surgery, depending on the cause.
3. Mixed Hearing Loss
Mixed hearing loss is a medical condition in which a person experiences sensorineural hearing loss and conductive hearing loss.
This means that damage has been done to the outer, middle, and inner ear.
As we’ve learned, you can treat conductive hearing loss with surgery or medication, but you can’t correct sensorineural hearing loss.
4. Unilateral Hearing Loss
Unilateral hearing loss is a condition in which a person has normal hearing in one ear and suffers hearing loss in the other.
Unilateral hearing loss can occur at birth. This is often hard to detect because a child can respond to environmental sounds and conversations and communicate like people without hearing disabilities.
This makes it hard to identify the hearing loss early enough to administer the appropriate treatment where necessary.
5. Auditory Neuropathy Spectrum Disorder (ANSD)
Auditory neuropathy spectrum disorder (ANSD) occurs when the ear’s hearing organ receives normally, but its signals are disorganized.
In some cases, the sound getting to the inner ear cannot be typically processed.
Although the causes of ANSD are not yet known, certain risk factors have been identified.
They include the following:
Jaundice at birth
Low birth weight
Family history of ANSD
There is no known cure for ANSD, but hearing aids can help patients properly process sound.
6. Central, Cortical or Auditory Processing Hearing Loss
This hearing loss occurs when the brain cannot interpret the sound information it receives despite the normal function of the peripheral hearing sensitivity.
Symptoms of Hearing Loss
Here are some symptoms of hearing loss:
Difficulty hearing consonants: This is especially true for people with mild and moderate hearing loss. Some people may be able to hear vowel sounds, but others cannot pick up vowel sounds.
Muffling of sound and speech: Sometimes, muffled speech doesn't just happen with low-level sounds; it also happens with normal or loud sounds.
Asking for repetition: Constantly asking for repetition during a conversation or asking the other person to speak loudly is a common hearing loss symptom.
Inability to understand speech: Difficulty understanding words or speech in a crowded place or background noise is another common symptom.
Volume increase: Turning up the radio or television volume to comprehend what is being said is a sign of hearing loss. This is often accompanied by difficulty hearing someone on the other end of a telephone call.
Conversation withdrawals: Withdrawal from conversations and avoidance of social settings is a sign of hearing loss.
Hearing Loss Causes
For the sake of this post, this section will be grouped into two; hearing loss causes in children and hearing loss causes in adults.
Hearing Loss Causes in Children
About 34 million children worldwide have disabling hearing loss. Hearing loss causes in children can be categorized under two major causes; Congenital causes and acquired causes.
Let's examine each cause.
1. Congenital Causes
Congenital hearing loss causes hearing loss from birth. 2 to 3 of every 1000 children born in the United States are born with hearing loss in one or both ears.
Congenital causes can either be hereditary or non-hereditary genetic factors.
Some of the factors responsible for congenital hearing loss are complications during pregnancy such as syphilis and maternal rubella, birth asphyxia, low birth weight, severe jaundice, or inappropriate use of drugs like diuretics during pregnancy.
2. Acquired Causes
Research has shown that over 90 percent of children born deaf have hearing parents.
Acquired hearing loss causes are factors that lead to hearing loss at any stage of the child's life; these causes are not genetic and have nothing to do with the child’s state at birth.
Preventable factors cause about 60 percent of childhood hearing loss.
Acquired hearing loss causes are often due to exposure to certain harmful things to the child’s hearing health.
Here are some acquired causes that can lead to hearing loss:
Otitis Media: 5 out of 6 children experience otitis media by the time they are three years old. This is the collection of fluid in the ear after a viral infection such as a cold.
Infectious Diseases: Infectious diseases like mumps, meningitis, and measles can degenerate to hearing loss if not properly handled.
Certain Medications: The use of certain medicines for malaria, tuberculosis, cancers, and neonatal infections can adversely affect a child’s hearing.
Exposure to Excessive Noise: There is a limit to how much noise the ear can handle; if a child is continuously exposed to loud noise, it can damage their hearing. Avoid prolonged exposure to loud recreational noise, machines, explosions, bars, nightclubs, and loud noises from audio devices.
Injury to the Head or Ear: Head injuries from falling or a massive impact from an object can tamper with a child’s hearing. Damage to the ear from sharp objects can also affect a child's hearing.
Hearing Loss Causes in Adults
Just like in children, hearing loss can be inherited or acquired as the person gets older. In this section, we will be examining the major causes of hearing loss in adults.
Let's get started.
1. Sudden Exposure to Loud Noise
When your ears are exposed to loud noise, the hair cells in the inner ear, which are responsible for hearing, can be flattened or damaged.
If the hair cells are flattened, the hearing loss will be temporary. If this damaged the hair cells, the hearing loss is permanent because damaged hair cells cannot be repaired or replaced.
According to the Environmental Protection Agency, 70 decibels is a safe noise level. The louder the noise beyond that safe level, the less time it takes to cause permanent hearing damage.
The sound level of a normal conversation is 60 decibels, while that of a dishwasher is 75 decibels. 75 decibels is considered within a safe range. Sound levels from 85 and above are risky. Noise from heavy traffic (85 dB), sandblasting (115 dB), snowmobiles (100 dB), and firearms (140-165 dB) can do serious damage to your ear.
2. Occupational Noise
Due to the danger of extended exposure to loud noise, you should not exceed maximum sound exposure durations. While we advise you to stay away from loud noise, certain occupations like the military and jobs involving heavy equipment constantly expose you to loud noise.
This is why these maximum sound exposure durations exist. It is also why hearing protection is so important.
The higher the sound level, the lesser the daily duration of exposure should be.
For instance, exposure to 90 decibels should not exceed 8 hours, 95 decibels is restricted to 4 hours, 100 decibels should not exceed 2 hours, 110 decibels should be restricted to 30 minutes daily, and exposure to 115 decibels should be restricted to fifteen minutes or less daily.
Asides from occupational noises, constant exposure to recreational activities with extremely high noise levels can also cause hearing loss. Activities such as snowmobiling and motorcycling can cause hearing loss.
Noise from clubs, concerts, and listening to loud music with headphones or earpieces can also cause hearing loss.
Presbycusis refers to hearing loss caused by aging. Presbycusis is often sensorineural, and it happens when the structures of the inner ear begin to degenerate.
This degeneration is the cumulative effect of age and exposure to loud sounds over time.
Age-related hearing loss is often characterized by difficulty in understanding speech, known as speech discrimination. Speech begins to sound unclear or muffled, and there is difficulty understanding high-pitched sounds.
What is particularly frustrating is that although the person may hear the sound of a voice, they cannot make out the meaning. It is like seeing someone's face but not being able to recognize the person.
Hearing loss caused by aging is gradual and may not be evident at the onset. Because it is progressive, you may not realize it until you begin to experience obvious symptoms like asking for repetition or increasing television volume beyond normal levels.
Age-related hearing loss often affects both ears and is usually permanent. This is because hearing loss is caused by the degeneration of hair cells in the inner ear. These hair cells cannot be regenerated or repaired once they are damaged. With the use of hearing aids, you may still be able to hear.
4. Tympanic Membrane Perforation
This is commonly known as a ruptured eardrum. The eardrum is a thin cone-shaped membrane that separates the middle ear from the external ear. It is responsible for transmitting sound from the air to the ossicles in the middle ear and the oval window in the cochlea.
The eardrum’s sole responsibility is to convert and amplify air vibrations to vibration in the cochlear fluid. It is not surprising that damage to the eardrum can cause hearing loss. The good news is that many eardrums perforated from trauma heal on their own within about six weeks.
Sudden changes in pressure can cause eardrum damage, as can sudden exposure to loud noise, poking the ear with an object, or an ear infection.
5. Ototoxic Medications
Ototoxic medications are medicines that can cause hearing loss as a side effect. Many prescription and non-prescription drugs are ototoxic; this is why you should talk with your doctor before taking any medication.
Most ototoxic drugs cause tinnitus before they degenerate to hearing loss. In most cases, if the drug is discontinued, the hearing loss will disappear, especially if it didn’t do serious damage to the ear.
Some drugs that can cause hearing loss include the following:
High doses of aspirin
Aminoglycoside antibiotics such as kanamycin, streptomycin, or neomycin
Certain anticancer chemotherapy drugs
Pop diuretics such as ethacrynic acid
6. Certain Ear Diseases
Several ear diseases can cause hearing loss. Let's examine the three most common ear diseases responsible for hearing loss.
Otosclerosis: This is a disease that affects the middle ear. Otosclerosis makes it difficult for the tiny bones (ossicles) in the middle ear to move. This prevents the transmission of sound from the middle ear to the inner ear. Otosclerosis causes conductive hearing loss, and surgery can correct it.
Autoimmune inner ear disease: Autoimmune inner ear disease is a medical condition that causes the body to attack the ears. The attack is similar to how the body will react to disease. The victim of this attack is the hair cells in the inner ear.
Autoimmune inner ear disease happens fast, so the hearing loss can be profound if immediate medical care is not given. However, immediate medical treatment may spare some hair cells, and the hearing loss will be minimal.
Ménière's disease: This is an inner ear disease with an unknown cause. Meniere's disease often results in sensorineural hearing loss, which will come and go at the initial stage and become permanent over time.
Rare Causes of Hearing Loss
Asides from the common causes of hearing loss we saw above, there are also rare causes of hearing loss.
Some of these health conditions are so rare that only a tiny percent of the world's population is affected by them.
Below are some of these rare conditions.
This rare condition affects one in every ten thousand people, and it is caused by a non-malignant cyst-like growth in the inner ear.
There are two types of cholesteatoma:
Congenital cholesteatoma is present at birth and happens when skin cells grow in the wrong place, which leads to growth behind the eardrum.
Acquired cholesteatoma happens in adults, and chronic or recurring ear infections can cause it.
Some symptoms of cholesteatoma are dizziness, smelly discharge from the ear, and hearing loss. If the cholesteatoma is left untreated, the growth’s toxicity can spread to other parts of the body and cause meningitis and brain abscesses. When left to grow, it can damage the inner ear structures, causing balance problems and dizziness.
This growth can also interfere with facial muscles and nerves and lead to facial paralysis. That said, surgeons can remove the cholesteatoma.
This condition causes the brain and ears to produce sound in disjointed ways. Some people refer to diplacusis as double hearing because loudness and pitch vary from ear to ear.
In some cases, patients hear an echo because one ear hears the sound faster than the other.
Diplacusis often causes the wearing out of inner ear hair cells.
If the diplacusis is caused by an infection or obstruction in the ear, the diplacusis disappears once the block is removed or the infection is cured. Still, if the disease-causing damage to the inner ear’s hair cells, that damage may be permanent.
3. Superior Semicircular Canal Dehiscence Syndrome (SCDS)
This disorder affects less than one percent of the world's population. It is caused by the presence of a tiny hole in a bone in the inner ear.
This hole causes balance disorders, vertigo, nausea, and extreme sensitivity to noise.
People with SCDS often complain that their voice, the sound of their pulse, and even the movement of their eyeball are too loud and unbearable.
This condition can be detected with a CT scan and corrected with surgery, but surgical complications like nerve damage and hearing loss may occur.
4. Cogan’s Syndrome
Cogan’s syndrome is a rare autoimmune inflammatory disease that causes the ears and eyes to swell.
Although the actual cause of Cogan’s syndrome is unknown, it is believed to be caused by an autoimmune response that makes the body's immune system attack the tissues of the ear and eye, resulting in swelling.
While some people with Cogan’s syndrome can manage their symptoms, others may suffer permanent visual and hearing damage.
5. Usher Syndrome
Usher syndrome is a disorder that affects a person’s hearing and vision. It is caused by the abnormal development of hair cells in the inner ear.
People with Usher syndrome can suffer profound hearing loss and severe balance problems. Usher syndrome is often inherited and can be present at birth.
There is no cure for Usher syndrome, but the hearing and vision problem can be managed using cochlear implants, hearing aids, and auditory training.
You can mostly avoid noise-induced hearing loss. Ensure you protect your ears from loud noises as much as possible. Limit the intensity and duration of exposure to loud noise in the workplace and at home.
Wearing earplugs and earmuffs will help protect your ear from destructive noise. Cut down on recreational activities that expose your ears to change in pressure or loud noise.
If you notice any problems with your ear, don't try to self-medicate or try DIY tricks for relief; head straight to the doctor's office and get examined.
“There are a variety of causes of hearing loss. Having a full medical evaluation by your healthcare provider and a good hearing test are the first steps to success.” - Drew Sutton, MD, Board-Certified Otolaryngologist.