Hearing loss is the gradual or sudden inability to fully perceive sound. About 28 million Americans have some level of hearing impairment, according to the National Institute on Deafness and Other Communication Disorders (NIDCD).

A person perceives sound when structures inside the ear convert sound wave vibrations into nerve signals, which are then perceived by the brain as individual sounds. Hearing loss can be temporary or permanent. Permanent hearing loss usually results from damage to the inner ear structure (called the cochlea) responsible for processing these nerve signals.

There are three major types of hearing loss:

• Conductive hearing loss. Occurs when the external or middle ear fails to work properly. This form of hearing loss generally can be reversed by treating the underlying condition that may be responsible.
  
  
• Sensorineural hearing loss. Usually occurs due to disorders of the cochlea in the inner ear. Aging is the most common cause of this type of hearing loss. This type of hearing loss generally is not reversible.
  
  
• Mixed hearing loss. Occurs as a result of both conductive and sensorineural factors

People who experience hearing loss may perceive a muffled quality to speech and other sounds. They often have difficulty in understanding other people's words. This problem tends to worsen in situations where there is a lot of background noise, such as in a room full of people. Various symptoms may be related to hearing loss. Ringing in the ears (tinnitus) is one of these symptoms.

Treatment options depend on the cause of a patient’s hearing loss. Patients whose hearing loss is related to earwax blockage usually can fully restore their hearing simply by having the earwax removed by a physician. Permanent hearing loss may be treated using artificial devices such as hearing aids, cochlear implants or personal listening devices.

Hearing loss is usually a natural and inevitable result of the aging process. Nonetheless, people can reduce the risk of hearing loss by using proper hearing protection in noisy environments and avoiding excessive noise whenever possible.

Hearing loss is the gradual or sudden inability to fully perceive sound. It is one of the most common health problems of older adults. One in three people over age 60 and half of people over age 85 have hearing loss, according to the National Institute on Deafness and Other Communication Disorders (NIDCD). Overall, approximately 28 million Americans have some level of hearing impairment.

A person perceives sound when sound waves reach structures inside the ear. The ear consists of the outer ear, middle ear and inner ear. Sound waves enter the outer ear and cause vibrations in a part of the middle ear known as the eardrum. Three small bones in the middle ear amplify the vibrations. These vibrations then pass through fluid in the snail-shaped structure of the inner ear (cochlea).

Along the cochlea, thousands of tiny hairs attached to nerve cells (neurons) translate sound vibrations into electrical signals. These signals are then transmitted up the eighth cranial nerve (known as the hearing nerve) to the brain. Each cochlear hair represents a sound frequency. Therefore, the way in which a sound stimulates the cochlear hairs determines the signals that are sent to the brain. This creates the perception of individual sounds.

Hearing loss usually results from damage to the cochlea that causes the tiny hairs to break or become bent. Another cause is the degeneration of the nerve cells used in hearing. In these cases, hearing loss is usually permanent. However, many other factors can contribute to both temporary and permanent hearing loss, such as blockage of the ear canal or damage to any of the structures in the ear.

People who experience hearing loss may perceive a muffled quality to speech and other sounds. They often have difficulty understanding others’ words. This problem tends to worsen in situations where there is a lot of background noise, such as in a crowded room. People with hearing loss may also find it especially difficult to hear higher tones.

Hearing loss can range from mild to severe and is measured using the pure-tone average (PTA). Generally speaking, the PTA measures the minimum strength of sound (decibels) that a person can easily hear. For example, someone with mild hearing loss may be diagnosed as having a PTA of 25 decibels, which means that the person has difficulty hearing sounds under 25 decibels (e.g., the purring of a cat). This degree of hearing loss may not be noticed by the patient and generally does not interfere with daily life. However, people with moderate to severe hearing loss may not be able to hear anything below 60 decibels, which is the level of sound commonly produced by a conversation. Someone with a PTA over 80 decibels is considered by most physicians to be deaf.

Loved ones may observe certain behaviors that indicate a person has hearing loss. People with hearing loss may ask others to speak more slowly, clearly and loudly. They may turn up the volume on the television or radio to excessive levels. In some cases, people with hearing loss may avoid conversations with others or become withdrawn in certain social settings.

Problems with hearing are among the most common major abnormalities in infants, according to the American Academy of Pediatrics (AAP). Hearing loss in both ears is present in one to three out of every 1,000 infants who are born healthy, and between two and four out of every 100 infants who need intensive care following birth. Hearing impairment is one of the most common forms of birth defects and can have profound consequences for the speech and language development of infants and children.

Some conditions may be confused with hearing loss. For example, asphasia – the inability to understand or use language as a result of damage to the brain – is sometimes mistaken for hearing loss. People with aphasia usually have no problems hearing language. However, they may appear confused when spoken to or claim that they do not understand what is being said. Additionally, some developmental disorders that affect verbal communication, such as autism, may be confused with hearing loss in their early stages. In most of these cases, hearing loss can be ruled out during diagnosis by conducting a simple hearing test.

Various symptoms may be related to hearing loss. Ringing in the ears (tinnitus) is one common symptom. Many people notice that their ears ring for a period of time after a loud concert. This form of tinnitus usually is temporary and disappears over time.

However, some cases of tinnitus are permanent. At least 12 million Americans have tinnitus, and at least 1 million of those people have tinnitus that is severe enough to interfere with daily activities, according to the National Institute on Deafness and Other Communication Disorders (NIDCD).

Other symptoms associated with hearing loss include:

• Vertigo (dizziness). Balance is controlled by a structure in the inner ear called the labyrinth. People who have hearing loss may also develop dizziness if the labyrinth is damaged or impaired.
  
  
• Drainage from the ear (otorrhea). Several factors can cause drainage of fluid from the ear. It is especially common in children, where it is usually the result of an ear infection.
  
  
• Earache (otalgia). Earache is a common symptom of infections of the ear, teeth or sinuses. People with severely impacted ear wax (a common cause of hearing loss) may also experience earache.

There are three major types of hearing loss:

• Conductive hearing loss. Occurs when the external or middle ear fails to work properly. In this type of hearing loss, sounds are blocked from entering the inner ear. Sources of this type of hearing loss include fluid buildup in the middle ear (often as a result of ear infections), buildup of wax in the ear canal or a perforated eardrum. This form of hearing loss generally can be reversed by treating the underlying condition responsible for the hearing loss.
  
  
• Sensorineural hearing loss. Occurs due to disorders of the cochlea in the inner ear. It may also be caused by damage to the hearing nerve or the parts of the brain that process speech (called retrocochlear hearing loss). Aging is the most common cause of sensorineural hearing loss. Gradual hearing loss as a result of aging is known as presbycusis, and it occurs in all people who live long enough to experience it. People who live or work in noisy environments may accelerate sensorineural hearing loss.
  
  Sensorineural hearing loss also may be present at birth (congenital) as a result of abnormal development of the cochlea, damage to the hearing nerve or inherited conditions. In other cases, hearing loss may result from conditions that occur after birth, such as meningitis. Conditions such as multiple sclerosis, stroke and tumors can also cause this type of hearing loss. Sensorineural hearing loss may range from mild to severe and generally is not reversible.
  
  
• Mixed hearing loss. When hearing loss is a result of both conductive and sensorineural factors, it is known as mixed hearing loss. It usually occurs in people whose permanent sensorineural hearing loss is compounded by a temporary conductive hearing loss, such as from a buildup of earwax.

In rare cases, a person may experience a complete loss of hearing, usually in one ear, that occurs suddenly or over a short period of time. This condition is known as sudden sensorineural hearing loss (SSHL) and affects up to 4,000 people in the United States each year, according to the National Institute on Deafness and Other Communication Disorders (NIDCD). It occurs most often between the ages of 30 and 60. Sometimes a loud pop is heard immediately before hearing is lost and many people with SSHL also experience dizziness and ringing in the ears (tinnitus). Although, in the vast majority of cases, the underlying cause of SSHL is unknown, the chances of patients recovering their hearing are usually good. However, because SSHL could indicate a more serious condition, anyone who experiences sudden deafness should consult a physician immediately.

Hearing loss can be caused by damage to any of the structures inside the ear. Sudden hearing loss is usually the result of disease or injury. Gradual hearing loss, on the other hand, is more often a result of years of wear and tear to part of the inner ear (cochlea). Over a person’s lifetime, daily exposure to noise causes the tiny hairs in the cochlea to bend or break. The nerve cells (neurons) of the cochlea may also degenerate. Once damage has occurred to the hairs or nerve cells, the electrical signals that transmit sound are not conducted as efficiently to the brain. This results in hearing loss.

This type of gradual hearing loss is more likely to occur in people over the age of 60. However, there are certain factors that can increase the rate and severity of hearing loss in people of all ages. For example, people who are regularly exposed to loud noises are at high risk for hearing loss at an early age. This may include exposure to occupational noise (e.g., construction or factory workers, musicians, airport workers), loud music, noisy engines (e.g., motorcycles, snowmobiles) or the sound of discharging firearms. In general, prolonged exposure to sounds louder than 90 decibels (roughly the level of sound that a subway train, motorcycle or lawnmower generates) can result in hearing loss. However, because wear and tear to the structures of the ear occurs gradually, the true extent of the damage might not be apparent until years later.

Hearing loss occurs more often in men than women, according to the National Institute on Deafness and Other Communication Disorders (NIDCD).

Certain diseases may cause hearing loss. Ménière disease causes an abnormality in the inner ear that results in a variety of symptoms including vertigo, tinnitus and fluctuating hearing loss. Paget’s disease causes an excessive amount of new bone growth, and in cases where it affects the skull, pressure on nerves may lead to hearing loss.

Other factors that can lead to hearing loss include:

• Ear infections and other illness. Ear infections create fluid that can interfere with the ability of the tiny bones in the middle ear to carry sound vibrations from the eardrum to the inner ear. In addition, certain illnesses may cause a high fever that can result in damage to the cochlea of the inner ear. Such illnesses include meningitis, mumps, measles, rubella and chickenpox.
  
  
• Auditory neuropathy. A type of focal neuropathy that affects the auditory nerve and interrupts the signals from the nerve to the brain. People with auditory neuropathy also tend to have profound speaking difficulties.
  
  
• Head injuries. A blow to the head or injury such as a skull fracture can impair hearing. For example, such injuries can change the position of the three bones of the middle ear, or cause an infection that creates fluid that interferes with the hearing process.
  
  
• Congenital factors. Some children are born with hearing loss that is present at birth and may be due to either hereditary factors or other factors that occur prenatally or during the birthing process.
  
  
• Ruptured eardrum. A tear or hole in the eardrum can interfere with the process of converting sound waves into nerve impulses that travel to the brain. Causes of eardrum ruptures include exposure to sudden loud noises, injury to the ear, foreign objects in the ear, ear infections or sudden pressure on the eardrum (such as during airplane takeoffs and landings).
  
  
• Certain medications. Medications such as antibiotics, diuretics and antimalaria drugs can cause toxic reactions in structures of the inner ear, which causes hearing loss or aggravates existing hearing problems.
  
  
• Tumors of the outer or middle ear. These can damage the structure of the inner ear.

Treatment options depend on the cause of a patient’s hearing loss. Hearing loss caused by disease can sometimes be resolved by treating the underlying cause. Additionally, patients whose hearing loss is related to earwax blockage usually can restore their hearing by having the earwax removed by a physician. A few drops of baby oil, mineral oil or glycerin may be inserted into the ear to loosen the wax. Warm water is then squirted into the ear, and the head is tilted until the wax drains out. In some cases, the physician may need to scoop out excess wax with a small instrument (curette) or suction device.

In some cases, hearing loss may be permanent. Treatment for patients with permanent hearing loss may be aimed at improving overall hearing ability using artificial devices, including:

• Hearing aids. Tiny battery-powered devices that fit into or behind a patient’s ear. These devices can make sounds louder and easier for a person to hear. Hearing aids contain a microphone that gathers sounds, an amplifier that makes sounds louder and an earpiece that transmits the sounds into the person’s ear. The louder sounds generated by hearing aids help stimulate the nerve cells (neurons) of the cochlea.
  
  
• Cochlear implants. An electronic device used to treat severe hearing loss by directly stimulating the hearing nerve. The device consists of a microphone placed behind the ear and a receiver and processor that are surgically implanted under the skin. Sounds picked up by the microphone are converted into electrical signals by the processor and transmitted to the brain through the hearing nerve. Cochlear implants are different from hearing aids. While hearing aids merely amplify sound, cochlear implants actually bypass the parts of the ear that are damaged. In the past, these devices have been used most often in children with congenital hearing loss. However, they are now being used more often in adults with severe hearing loss.
  
  
• Personal listening systems. Devices that amplify and isolate sounds to help people hear more clearly. They are sometimes called assisted listening devices. Personal listening systems generally consist of a microphone, a transmitter (usually FM or infrared) and an earpiece. These devices help people listen to the sounds they want to hear while reducing or eliminating other sounds in the environment. There are also devices available to amplify the sound of specific equipment, including televisions and telephones.   

Surgery often helps enhance hearing in patients with hearing loss. In some cases, surgery can be used to treat the underlying cause of hearing loss, such as removing a tumor. Although surgical procedures cannot cure sensorineural hearing loss, they can slow the progress of some types of hearing loss.

Children who have hearing loss as a result of recurrent ear infections may be fitted with ear tubes (myringotomy). In this surgical procedure, small tubes are inserted into the eardrum to allow fluid to flow out. In roughly 14 months, the incision in the eardrum heals and the tubes fall out of the ear.

Patients whose hearing loss is profound and untreatable may benefit from learning to lip read.

Hearing loss is often a natural and inevitable result of the aging process. Nonetheless, people can take various steps to slow the progression of hearing loss by avoiding excessive noise. People who work in noisy workplaces are encouraged to ask their employer for proper hearing protection, such as specially designed earphones that block out excessive noise.

Over-the-counter earplugs made of plastic or rubber also are available to protect the ears from noise. People are urged to wear these earplugs when engaging in activities that include exposure to loud sounds, such as riding snowmobiles, discharging firearms or attending loud concerts.

Whenever possible, people are urged to avoid exposure to loud sounds. This includes avoiding listening to music at loud volumes. Loud music is particularly damaging for those who wear earphones. People are encouraged to make sure to keep the volume of personal music players (e.g., mp3 players, CD personal stereos) at a level that allows them to carry out a conversation with other people. Generally, this means that the volume level of a personal music player should be set no higher than 60 percent of its maximum.

Finally, people who are regularly exposed to loud sounds should consider having their hearing tested on a periodic basis. This can help reveal early hearing loss and encourage the individual to take steps to avoid additional hearing damage.

Preparing questions in advance can help patients to have more meaningful discussions with healthcare professionals regarding their condition. Patients may wish to ask their doctor the following questions related to hearing loss:

1. What are the initial signs that I might have hearing loss?
   
   
2. How will you diagnose my hearing loss?
   
   
3. What type of hearing loss do you suspect I have?
   
   
4. What could be causing my hearing loss?
   
   
5. What are my treatment options?
   
   
6. What are the side effects of these treatments?
   
   
7. How much of my hearing is likely to be restored?
   
   
8. What is my long-term prognosis?
   
   
9. I work in a noisy environment. How often should I have my hearing tested?
   
   
10. I have excessive earwax. Is there any way to prevent this wax buildup?