What is hearing loss?

Quick Answer
Loss of sensitivity to sound as a result of disease, infection, injury, noise, or aging.
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Causes and Symptoms

The causes of hearing loss vary, although three major factors enhance the progression of loss as one ages: exposure to noise, previous middle-ear disease, and vascular disease. There are basically two types of hearing loss, conductive hearing loss and sensorineural hearing loss. Conductive hearing loss results from interference with sound vibration through the external and middle ear. In other words, the sound cannot get to the inner ear. In some types of conductive hearing loss, if the sound amplitude is increased enough, then the person may be able to hear. Possible reasons for conductive hearing loss include impacted or large amounts of cerumen (wax) in the ear, foreign bodies (such as soap, food, or insects) in the ear canal, otitis media (middle-ear infection), rheumatoid arthritis, and otosclerosis, in which the stapes becomes fixed to the oval window of the cochlea. Sensorineural hearing loss is caused by damage to the inner ear, the auditory nerve, or the brain.

Earwax buildup is a common and treatable cause of conductive hearing loss. There have been reports that as much as 25 percent of nursing home residents have impacted cerumen. Older adults can be taught how to remove the wax on their own. Cerumenex (by prescription only) and Debrox (sold without a prescription) can be used as directed, followed by lavage to remove the wax and residual medication. Some health care providers recommend the instillation of mineral oil into the ear canal twenty-four hours before removal to help soften the wax, followed by lavage with one part hydrogen peroxide to three parts water at room temperature.

Sensorineural hearing loss means the presence of disease anywhere from the organ of Corti to the brain. The result is loss of hearing high tones, for it is the hair cells in the basal curvature of the organ of Corti that are sensitive to high tones. Presbycusis is sensorineural hearing loss caused by aging of the inner ear. The onset of presbycusis may begin anytime from the third to the sixth decade of life, depending on type. Presbycusis affects more than 50 percent of individuals over age sixty-five. Older adults suffering from these disturbances show distinct and differing audiograms, which are used clinically to diagnose types of impairment. The standard type of presbycusis with hearing loss at high Hertz is often associated with sensory and neural presbycusis. There are four types of presbycusis: sensory, neural, metabolic, and cochlear conductive.

The elderly first start to lose hearing in the high-frequency range. High-frequency consonants and sibilants become more difficult to recognize—for example, f, g, l, t, s, ch, sh, and th. In presbycusis, high-frequency sounds become unintelligible. Understanding spoken words depends largely on the clear perception of high-frequency consonants rather than low-frequency vowel sounds. This is why words starting with the above letters or combinations become unintelligible. Many times, older adults have both conductive and sensorineural frequency losses. The precise cause of the defect requires help from a specialist and the use of sophisticated audiometric testing.

The sound waves that travel through the ear have two main characteristics, frequency and amplitude. Frequency is related to the pitch of a sound and is measured by the number of vibrations or cycles per second. The higher the vibration frequency, the higher the perceived pitch of the sound. Hertz (Hz) is the unit of measurement to denote cycles per second. Amplitude is related to the loudness of a sound. The greater the intensity with which a sound strikes the eardrum, the louder the tone. The unit of measurement of intensity of sound is decibels (dB).

Among the offenders to hearing are radio headphones, lawn mowers, diesel trucks, heavy machinery, and loud music. A single very loud noise can damage the middle ear. An eardrum can be broken by sounds reaching 160 decibels to 1,000 Hertz. Also, continuous noise of more than 80 to 85 decibels can cause harm to hearing. Normal conversation is measured at 60 decibels. A noisy restaurant, a vacuum cleaner, an electric shaver, and a screaming child can reach decibels between 80 and 85 decibels. Louder everyday noises include a blow-dryer (100 decibels), a subway train (100 decibels), and a car horn (110 decibels). Anyone exposed to noise in the 80 decibel range should wear hearing protection.

Another common hearing problem is tinnitus (ringing in the ears). Medications such as aspirin, aminoglycoside antibiotics, and diuretics can cause toxic effects to the hair cells of the organ of Corti, thereby resulting in sensorineural hearing loss. Tinnitus, an internal noise generated within the hearing system, occurs in many types of hearing disorders at all ages, but it is reported more frequently in the elderly. Tinnitus affects seven million people, of which 10 to 37 percent are elderly, and that number is growing. The ringing sound is generally high pitched with sensorineural loss and low pitched with conductive hearing loss. However, tinnitus may be present with or without hearing loss. Some types of tinnitus do not usually awaken people out of sleep nor do they interfere with leisure activities. Older adults can attempt to alleviate the condition through biofeedback or by disguising the sound. Soft radio music and other distracting sounds may offer some comfort.

Treatment and Therapy

There are many treatments for hearing loss and, depending on the type of loss, some treatments work better than others. For example, with conductive hearing loss, if the cause is excessive earwax buildup, then the results can be remarkable when the wax is removed. For both types of hearing loss, conductive and sensorineural, simple measures can be used to facilitate better communication.

One technique that can help in communicating with someone with hearing loss is facing the person when speaking, so that he or she can see one’s face and lips. Using simple, short sentences or phrases and speaking slowly in a low voice can be helpful. Loudness is not helpful and can be irritating, whereas a low voice enables people to hear lower frequencies, which usually can be heard more easily.

Although hearing aids may help certain types of hearing loss, many people do not like to use them. A person wearing such a device for the first time needs to go through an adjustment period, and some older adults do not give themselves enough time to get used to the hearing aid. Some hearing aids have been known to cause irritation to the external ear. Also, the increased humidity within the external auditory canal may cause infectious otitis externa.

There are basically three kinds of hearing aids: the body type, the behind-the-ear-type, and in-the-ear type. The body type resembles a handheld amplifier with a wire that attaches to an earpiece. The behind-the-ear type is worn behind and in the ear. A person with poor eyesight and rheumatoid arthritis would probably benefit from the body type or behind-the-ear type. These types are easier to see and handle because of their larger size. The in-the-ear devices are small and cosmetically more acceptable, but they are more difficult to manipulate. The selection often depends on the wearer’s personal preference, vision capabilities, and manual dexterity.

It takes time to adjust to using a hearing aid. Sounds and voices are made louder, not clearer. The wearer must become accustomed to the background noise. Often, the user must be encouraged to continue using the hearing aid during this adjustment period. The greatest satisfaction is achieved with hearing aids if hearing loss is between 55 and 80 decibels. There is only partial benefit if the loss is greater than 80 decibels.

Perspective and Prospects

Hearing is regarded by some to be the most important of the five senses. It is imperative for people to protect their hearing for as long as they can. In today’s world, where excessive noises are bombarding eardrums everyday, people need to protect themselves.

Hearing loss occurs when hair cells in the ear are damaged or destroyed by excessively loud noise or moderately loud noise for prolonged periods of time. Hearing loss usually occurs gradually and without pain. Over time, sounds become muffled and higher frequency sounds become hard to distinguish. Normal conversation occurs around 60 decibels. Anything higher than 60 decibels for extended periods of time may lead to hearing loss. According to the Ear Institute in Los Angeles, about 30 percent of hearing loss is due to exposure to loud sounds.

There are ways to reduce excessive noise levels in the environment. First, the time exposed to loud noises should be limited. This can be accomplished by removing the sound or decreasing the volume. The popular audio products now on the market can pose a risk to hearing. Most people are not aware of the potential dangers of listening to music at high volumes. A person listening to music by wearing earphones should not be heard by the person standing next to them. Similarly, a loud device such as a vacuum cleaner should be operated for no more than ten minutes at a time, with a five-minute break between uses.

It is interesting to note that hearing loss results from both loudness and time exposure. For example, a one-time gunshot noise near the ear can be just as damaging as extended exposure to loud music at 120 decibels for fifteen minutes or more. Anyone working in an environment that reaches noise levels of more than 85 decibels for extended periods of time should wear protective devices. Earplugs and hearing protection devices are needed for construction workers, traffic personnel, musicians, disc jockeys, air traffic personnel, nightclub employees and patrons, or anyone exposed to loud noises.

Scientists are conducting research to discover whether damaged hair cells of the ear are capable of rebuilding their structure over a forty-eight-hour period (the time that it takes for hearing to return after a temporary loss). Researchers speculate that permanent hearing loss may occur when self-repair mechanisms are compromised.

Scientists are studying blood flow in the cochlear section of the ear to evaluate how drugs may affect hair cells. Researchers are also examining blood flow to the cochlea when people are exposed to conversational sound and loud sounds. It seems that when a person is exposed to loud sounds, the blood flow in the cochlea drops. Drugs that are used to treat blood flow problems, such as in peripheral vascular disease, may show a benefit to maintaining blood flow to the cochlea. These and other drug therapies may show promising results in helping people with hearing loss. Finally, with a reduction in harmful noise, hearing loss will decrease.

Bibliography

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Carson-DeWitt, Rosalyn. "Hearing Loss." Health Library, September 10, 2012.

Craine, Michael. Hear Well Again: A Step by Step Program to Better Hearing. Chapel Hill, N.C.: Professional Press, 1999.

Gallo, Joseph J., et al., eds. Handbook of Geriatric Assessment. 4th ed. Sudbury, Mass.: Jones and Bartlett, 2006.

"Hearing Loss." Medline Plus, May 22, 2012.

"Hearing Loss." National Institute on Aging, April 30, 2013.

Mahoney, Janet. “Hearing Loss and Assessment: A Concern for All.” Nursing Spectrum 13, no. 1 (January 10, 2000).

Paterson, J. “What You Need to Know About Hearing Loss.” USA Weekend, November 21, 1997.

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Tabloski, Patricia A. Gerontological Nursing. 2d ed. Upper Saddle River, N.J.: Pearson, 2010.

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