Hearing loss is deterioration in hearing. Deafness is profound hearing loss.
Among the older population, 29% have significant hearing loss by age 65 and 50% by age 80. Hearing loss can have a profound effect on quality of life, especially when it interferes with the ability to hear and understand speech. Many older people who develop hearing loss also have impaired vision, and the combination can greatly interfere with the ability to carry out everyday activities.
Several characteristics of sound, including loudness and pitch, affect the ability to understand sounds created by speech. For example, hearing loss may involve the inability to hear words below a certain threshold of loudness. Hearing loss may also involve the inability to discriminate among similar-sounding words, depending on loudness and pitch.
Even mild hearing loss makes understanding speech difficult. As a result, an older person with mild hearing loss may avoid conversations. Understanding speech may be particularly difficult if there is background noise or more than one person is talking, such as in a restaurant or at a family gathering. Thus, hearing loss can lead to social isolation, inactivity, loss of social support, and depression. In a person with dementia, hearing loss can make communicating even more difficult. Hearing loss can cause both emotional and physical harm. A person who has trouble hearing, for example, may not hear a fire alarm, a smoke detector, or an automobile horn.
Hearing aids can improve quality of life for about 95% of older people with hearing loss. However, only 30 to 40% of older people with hearing loss in the United States use hearing aids. Those people who cannot benefit from hearing aids may be helped by a cochlear implant.
One of the important barriers to coping with hearing loss is overcoming the embarrassment that some older people experience. Wearing a hearing aid or letting someone know that they are "hard of hearing" makes some older people feel old. Hearing loss, however, is a medical condition and is nothing to be ashamed of. By facing the reality of hearing loss, people can do so much to improve their lives.
The gradual loss of hearing that affects many older people is called presbycusis. Presbycusis may begin in a person's 20s but go unnoticed until the person reaches his 50s or 60s.
Aging itself plays a role in the development of presbycusis, but noise is probably the most common cause. Noise destroys the small hairlike projections in the cochlea that conduct sound. Both the loudness and duration of noise exposure are important. A single exposure to a very loud noise can cause hearing loss, but such hearing loss is usually temporary. However, repeated exposure to loud noises usually causes permanent hearing loss. Millions of people in the United States are repeatedly exposed to levels of noise that can damage hearing. Typically, each exposure causes hearing loss that is so subtle as to be imperceptible. Only after decades of cumulative noise exposure and damage does hearing loss become noticeable.
Some drugs, including gentamicin and related antibiotics (aminoglycoside antibiotics), cisplatin (a chemotherapy drug), aspirin and related drugs (salicylates), and furosemide and related diuretics (loop diuretics), can cause hearing loss. Aspirin can cause ringing in the ears (tinnitus); this is generally temporary and occurs only at high doses. Quinine occasionally causes similar symptoms.
Blockage of the ear canal by earwax is a common cause of mild hearing loss among older people. People who swim in cold water for many years may develop blockages due to bony projections in the ear canal (exostoses). Although usually of little significance, these bony projections can cause wax and dead skin to accumulate. Less often, the ear canal is partly or completely blocked by changes in the skull due to abnormal bone growth (Paget's disease).
Much less common causes of hearing loss include rupture of the eardrum; infection or allergy that causes fluid to develop behind the eardrum; blockage of the ear canal by a foreign object; a tumor of the auditory nerve, brain, or eustachian tube; strokes; and disorders in which a person's own immune system turns against the body in some way (autoimmune disorders).
For additional detail on this topic, see Two Categories of Hearing Loss: Conductive and Sensorineural.
Hearing loss due to aging itself usually develops so gradually that people may not notice the first symptoms. High-pitched sounds are affected more than low-pitched sounds. The voices of women and children, therefore, which are higher in pitch than those of men, become particularly difficult to understand. High-pitched musical instruments, such as violins, may sound dull. In addition, certain consonants, such as C, D, F, K, P, S, and T, become hard to distinguish. An inability to hear the sounds of some consonants may make it sound as if a speaker is mumbling. Words can be misinterpreted. For example, a person may hear "bone" when the speaker said "stone."
Conversations become difficult to follow, particularly in crowded or noisy areas. Constantly asking others to talk louder can frustrate both the listener and the speaker. People with hearing loss may misunderstand a question and give an apparently bizarre answer, leading others to believe they are confused. They may misjudge the loudness of their own speech and thus shout, discouraging others from conversing with them.
Background noise tends to mask high frequencies and blur sounds, making speech more difficult to understand even for older people who hear normally. To compensate for background noise, many older people develop an ability to watch a person's lips for clues about what is being said.
During an examination, a doctor may test a person's hearing by whispering or by using a hand-held sound generator. In addition, the doctor may place a vibrating tuning fork near the person's ear, on the top part of the skull, or on the bone behind the ear. A person's symptoms and the results of the examination can be important in establishing the diagnosis. However, special diagnostic tests usually are performed as well.
- Audiometry is the first hearing test performed. In this test, a person wears headphones that play tones of different pitch and loudness. The person signals when he hears a tone, usually by raising his hand or pressing a button on the side that he heard the tone. For each pitch, the test identifies the quietest tone the person can hear in each ear.
- Speech threshold testing measures how loudly words have to be spoken to be understood. A person listens to a series of two-syllable, equally accented words, such as "railroad," "stairway," and "baseball," presented at different volumes.
- Speech discrimination testing assesses the ability to hear differences between words that sound similar. Pairs of similar one-syllable words are presented, such as "snake" and "flake."
Other tests are less commonly done. They include tests (1) to measure nerve impulses in the brain produced by sound vibrations in the ears; (2) to measure the ability to interpret and understand distorted speech; (3) to understand a message presented to one ear when a different, competing message is presented to the other ear; (4) to combine incomplete messages to each ear into a meaningful message; and (5) to determine where a sound is coming from.
If a person has fluid in the ear, the doctor examines the back of the throat with a mirror or viewing tube (endoscope). Occasionally, imaging studies (such as computed tomography [CT] or magnetic resonance imaging [MRI]) are done to check for sinusitis or a tumor, especially when a person has significantly greater hearing loss in one ear along with dizziness or ringing in the ears.
Unfortunately, most hearing loss in older people cannot be cured. However, some treatments can compensate for hearing loss and improve quality of life. Hearing aids, for example, can benefit most people with mild to moderate hearing loss. Cochlear implants can benefit people with severe or profound hearing loss.
Hearing aids: Hearing aids increase the volume of sound reaching the eardrum. They are helpful regardless of the cause of hearing loss and significantly improve a person's ability to communicate. If hearing loss occurs in both ears, as is the case with most older people, wearing a hearing aid in each ear achieves the best results. However, if hearing loss is much greater in one ear than in the other, a single hearing aid worn in the more impaired ear may work best.
See the figure Hearing Aids: Amplifying the Sound.
Hearing aid technology continues to improve. People who have been dissatisfied with older models may be pleasantly surprised by more recently developed hearing aids. A comprehensive hearing aid center can help people choose a hearing aid that best meets their specific needs. A 30-day trial period is usually offered at such centers.
All hearing aids have a microphone that picks up sounds, a battery-powered amplifier that amplifies sounds, and a means of transmitting the sounds to the person. Some recent hearing aids have several microphones. Most hearing aids transmit the sounds through a small speaker placed in the ear canal. Much less common are hearing aids that require surgical implantation, allowing sounds to be transmitted directly to the tiny bones of the middle ear or to the skull instead of through a speaker. Implanted devices eliminate feedback (squealing), which is common in conventional hearing aids. A person with an implanted device also feels less of a sense that the ear is plugged.
Hearing aids differ in size and in where they are worn. Small hearing aids fit entirely or almost entirely in the ear canal. They generally are more attractive because they are less noticeable. However, their small size may limit the number of features they offer and the ease with which their controls can be adjusted or batteries replaced.
Hearing aids also have different electronic characteristics to suit a person's particular needs. For example, people whose hearing loss affects mainly higher frequencies do not benefit from amplification of all sound frequencies, which merely makes the mumbled speech they hear louder. Hearing aids that selectively amplify the high frequencies markedly improve speech recognition and sound clarity. Most older people need this type of hearing aid, which must be adjusted for a person's specific hearing deficits. Other hearing aids contain vents in the ear mold, which increase the passage of high-frequency sound waves into the ear. As a result, high-frequency sounds become clearer.
Some digital hearing aids can match amplification even more precisely with the person's hearing loss. People who cannot tolerate loud sounds may need hearing aids with special electronic circuitry that keeps the maximum volume of sound at a tolerable level. Hearing aids with complex features tend to be the most expensive but are often essential.
People with dementia may fare best with a simple style of hearing aid that resembles a portable radio that can be worn on a belt buckle or tucked into a pocket. The device consists of a box containing an amplifier, a microphone or microphone jack, a headphone jack, and a volume control. The wearer plugs a conventional headphone into the amplifier. Compared with conventional hearing aids, this device is relatively inexpensive, easily repaired if broken, and more difficult to lose.
Cochlear implants: People with severe or profound hearing loss who cannot benefit from hearing aids may benefit from a cochlear implant. Cochlear implants combine an external microphone, external processor, and external coil with electrodes inserted surgically into the cochlea and a coil inserted surgically into the skull above and behind the ear. Cochlear implants provide electrical signals directly into the auditory nerve. Cochlear implants do not restore normal hearing. However, they do help almost everyone who gets them to better distinguish spoken words, with or without reading lips, and, for some, a greater ability to understand telephone conversations. Cochlear implants also help deaf people hear and distinguish environmental and warning signals, such as doorbells, telephones, and alarms.
Other ways to cope with hearing loss: If hearing cannot be fully restored, a person can adapt in other ways.
Alerting systems that use a flashing light or a wearable vibrating alarm enable people to know when the doorbell or telephone is ringing or when a person in another room is calling out for help. Similarly, safety devices (such as smoke detectors, carbon monoxide detectors, and motion sensors) and timers can be equipped with a flashing light.
Special sound systems can help people hear in theaters, churches, and other places where there is competing noise. Many television programs carry closed captioning, in which the dialog is shown as text. Telephone communication devices, called text telephones (TTY or TTD), display the words of the caller on a screen.
Lip reading (speech reading) and other strategies for coping with hearing loss are part of a program of aural rehabilitation. Lip reading is particularly helpful for people who can hear but who have trouble discriminating certain consonant sounds, as in hearing loss that occurs with aging. Speech comprehension can be significantly improved by observing the position of a speaker's lips.
In addition to training in lip reading, people are taught how to anticipate difficult communication situations and to modify or avoid them. For example, people can visit a restaurant during off-peak hours, when it is quieter. They can ask for a booth, which blocks out some extraneous sounds. They can request that "specials of the day" be written rather than spoken. In direct conversations, people may ask the speaker to face them, to allow for lip reading. At the beginning of a telephone conversation, people can identify themselves as being hearing-impaired.
See the sidebar Preventing Noise-Induced Hearing Loss.
See the sidebar Hearing Aids and the Telephone.