Presbycusis
What is presbycusis?
Presbycusis is the loss of hearing that gradually occurs in most
individuals as they grow older. Hearing loss is a common disorder
associated with aging. About 30-35 percent of adults between the
ages of 65 and 75 years have a hearing loss. It is estimated that
40-50 percent of people 75 and older have a hearing loss.
The loss associated
with presbycusis is usually greater for high-pitched sounds.
For example, it may be difficult for someone to hear the nearby
chirping of a bird or the ringing of a telephone. However, the
same person may be able to hear clearly the low-pitched sound
of a truck rumbling down the street.
There are many
causes of presbycusis. Most commonly it arises from changes
in the inner ear of a person as he or she ages, but presbycusis
can also result from changes in the middle ear or from complex
changes along the nerve pathways leading to the brain. Presbycusis
most often occurs in both ears, affecting them equally. Because
the process of loss is gradual, people who have presbycusis
may not realize that their hearing is diminishing.
What
are the symptoms of presbycusis?
With presbycusis, sounds often seem less clear and lower in
volume. This contributes to difficulty hearing and understanding
speech. Individuals with presbycusis may experience several
of the following:
- The speech of
others seems mumbled or slurred.
- High-pitched
sounds such as "s" and "th" are difficult to hear and tell
apart.
- Conversations
are difficult to understand, especially when there is background
noise.
- A man's voice
is easier to hear than the higher pitches of a woman's voice.
- Certain sounds
seem annoying or overly loud.
- Tinnitus (a ringing,
roaring, or hissing sound in one or both ears) may also occur.
What
are the causes of presbycusis?
Sensorineural
hearing loss is caused by disorders of the inner ear or auditory
nerve. Presbycusis is usually a sensorineural hearing disorder.
|
Image of the inner ear
|
It is most commonly
caused by gradual changes in the inner ear. The cumulative effects
of repeated exposure to daily traffic sounds or construction work,
noisy offices, equipment that produces noise, and loud music can
cause sensorineural hearing loss. Sensorineural hearing loss is
most often due to a loss of hair cells (sensory receptors in the
inner ear). This can occur as a result of hereditary factors as
well as aging, various health conditions, and side effects of
some medicines (aspirin and certain antibiotics).
Presbycusis may
be caused by changes in the blood supply to the ear because
of heart disease, high blood pressure, vascular (pertaining
to blood vessels) conditions caused by diabetes, or other circulatory
problems. The loss may be mild, moderate, or severe.
Sometimes presbycusis
is a conductive hearing disorder, meaning the loss of sound
sensitivity is caused by abnormalities of the outer ear and/or
middle ear. Such abnormalities may include reduced function
of the tympanic membrane (the eardrum) or reduced function of
the three tiny bones in the middle ear that carry sound waves
from the tympanic membraine to the inner ear.
What
can be done?
Much of the
hearing loss caused by noise exposure can be prevented. Awareness
of potential sources of damaging noises, such as firearms, snowmobiles,
lawn mowers, leaf blowers, woodworking machinery and loud appliances
is important. Ear plugs or special fluid-filled ear muffs can
give protection and should be worn to help avoid the possibility
of damage to hearing. Excessively loud everyday noises, both
at home and at work, can pose a risk to a person's hearing.
Avoiding loud noises and reducing the amount of time one is
exposed to everyday noises may be helpful.
There are many
strategies to help people with presbycusis. Hearing aids may
be recommended for some individuals. Assistive listening devices
can provide further improvement in hearing ability in certain
situations. One example of such a device is the built-in telephone
amplifier. Another example is FM systems that make sounds clearer,
with or without a hearing aid, by delivering sound waves like
a radio. Training in speechreading (using visual cues to determine
what is being spoken) can help those with presbycusis to understand
better what is being said in conversations or presentations.
How
is a hearing aid selected?
Consultation
with specially trained professionals who work as a team is important
for evaluation of a hearing loss and selection of appropriate
management. An otolaryngologist (ear, nose and throat specialist)
should evaluate the individual with a hearing problem to make
the diagnosis and exclude related systemic disorders that may
contribute to the problem. An audiologist is a professional
who measures the hearing and identifies the type of hearing
loss. The audiologist conducts a complete hearing evaluation
and determines if a hearing aid may be useful. The individual
is counseled about how a hearing aid may improve listening situations.
Then the audiologist conducts tests to find an appropriate aid,
selecting one that maximizes a person's hearing and understanding
of speech. Most older adults with hearing loss can benefit from
using a hearing aid, although the degree of benefit may vary
according to the type and amount of hearing loss.
Communication
tips
If you have
a hearing loss caused by presbycusis or know someone who does,
share these tips with family members, friends, and colleagues.
- Face the person
who has a hearing loss so that he or she can see your face
when you speak.
- Be sure that
lighting is in front of you when you speak. This allows a
person with a hearing impairment to observe facial expressions,
gestures, and lip and body movements that provide communication
clues.
- During conversations,
turn off the radio or television.
- Avoid speaking
while chewing food or covering your mouth with your hands.
- Speak slightly
louder than normal, but don't shout. Shouting may distort
your speech.
- Speak at your
normal rate, and do not exaggerate sounds.
- Clue the person
with the hearing loss about the topic of the conversation
whenever possible.
- Rephrase your
statement into shorter, simpler sentences if it appears you
are not being understood.
- In restaurants
and social gatherings, choose seats or conversation areas
away from crowded or noisy areas.
How
does hearing work?
- The outer ear
collects sound waves and works like a funnel to send them
through a narrow tube (ear canal) that leads inside the ear.
At the end of the ear canal is the eardrum (tympanic membrane).
- The tympanic
membrane is a thin membrane that vibrates when sound waves
strike it. It divides the area called the outer ear from the
middle ear. It is attached to a set of three tiny bones in
the middle ear.
- These bones
are called the hammer (malleus), anvil (incus), and the stirrup
(stapes). The bones pass the vibrations of sound waves to
a small organ in the hearing part of the inner ear called
the cochlea, which is a coiled structure like a snail shell.
- The inner ear
is filled with a thin fluid that transmits pressure changes
throughout the cochlea. Inside the cochlea are tiny hair cells
that pick up sound vibrations from the fluid and cause nerve
impulses in the auditory nerve.
- The auditory
nerve carries the message to the brain, where it is interpreted
as sound.
Where
can I get additional information?
October 1997
Updated April 1999
NIH Pub. No. 97-4233 |
|
.gif)
