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What causes hearing loss? Can
it be prevented?
Normal hearing requires that all parts of the auditory
pathway are working correctly. This pathway includes the external ear,
middle ear, inner ear, auditory nerve, and the connection between the
auditory nerve and the brain. The exact location and nature of the problem
in the auditory pathway determines the type and severity of a person’s
hearing loss.
Some causes of hearing loss occur before a baby is
born. These include genetic disorders (such as Waardenburg syndrome or
Crouzon syndrome) and infections (such as congenital rubella or congenital
syphilis).
About half of all cases of hearing loss among children
are thought to result from genetic factors. Sometimes these children have a
syndrome of which hearing loss is only one feature. However, in most
children with hearing loss that is due to a genetic cause, the hearing loss
is not part of a syndrome. A variant of the connexin 26 gene is responsible
for much of the hearing loss in this latter group of children. [Read
about the connexin 26 gene]
To learn more about a specific genetic condition that
you think could cause hearing loss, go to the National Library of
Medicine's Genetics Home Reference Web site. Information about each genetic
condition includes symptoms, how common it is, related genes, treatments,
and links to resources where you can learn more about the condition. The
Genetics Home Reference also can help you learn more about genetics,
including genetic testing, genetic counseling, and gene therapy. [Go to the
Genetics Home Reference Web site]
You can also learn more about the genetics of hearing
loss by reading the parent's guide to genetics on the CDC Early Hearing
Detection and Intervention Web site. The guide describes the “All Ears”
study, whose purpose is to help us understand both genetic and
environmental causes of hearing loss in babies and young children. [Read A
Parent’s Guide to the “All Ears” Study]
Problems during or soon after birth can also be risk
factors for developing hearing loss. These include hypoxia (where the baby
does get not enough oxygen), bleeding in the brain, and hyperbilirubinemia
(severe jaundice). Children who are born early or at low birth weight are
more likely to have problems that may lead to hearing loss. However,
children who are normal birth weight can have hearing loss.
Hearing loss can also occur later in a child’s or
adult’s life. Causes during this time include infection (such as
meningitis, chronic middle ear infections, or measles), injuries (such as
head injury), or certain drugs (such as the antibiotic gentamicin). High
noise levels (such as from firecrackers or loud rock concerts) can also
damage a person’s hearing. About 30 million workers are exposed to
dangerous noise levels on their jobs. Another nine million are at risk of
hearing loss as a result of working with certain metals or solvents.
Some causes of hearing loss can be prevented. For
example, vaccines can prevent certain infections, such as H-flu meningitis
or measles, that can cause hearing loss. Another cause that can be
prevented is kernicterus, a kind of brain damage that happens when a
newborn baby has too much jaundice. Kernicterus can be prevented by using
special lights (phototherapy) or other therapies to treat babies with
jaundice. [Read more
about kernicterus]
To find CDC guidelines on preventing hearing loss,
visit the "CDC Recommends: The Prevention Guidelines System" Web site and
search on "deafness" or "hearing loss". The guidelines include information
about hearing loss caused by noise, congenital syphilis, congenital
rubella, and other conditions. [Go
to CDC Recommends: The Prevention Guidelines System.]
WISE EARS!® is a national program to prevent
noise-induced hearing loss. It was created by the National Institute on
Deafness and Other Communication Disorders, the National Institute of
Occupational Safety and Health, and other agencies. The program has
materials for kids, teachers, parents, the media, and the general public.
It helps people learn what noise-induced hearing loss is, what causes it,
and how to prevent it. [Go
to the WISE EARS!® Web site]
People who work in noisy places can prevent hearing
loss by using hearing protectors. You can learn how to choose the right
protector for you at the National Institute of Occupational Safety and
Health’s Hearing Loss Prevention Web site. The site also has information
about other ways to protect your hearing on the job. [Go
to the Hearing Loss Prevention Web site]
Healthy People 2010 is a national effort to promote
health and prevent disease. It includes goals related to hearing loss, such
as increasing the number of newborns who are screened for hearing loss by 1
month of age, diagnosed by 3 months of age and receiving intervention
services by 6 months of age; increasing the use of ear protection devices;
decreasing the number of people who have noise-induced hearing loss, and
increasing the number of people who get their hearing checked regularly.
The National Institute on Deafness and Other Communication Disorders' "Healthy Hearing 2010"
Web site provides more
information about hearing-related goals in Healthy People 2010. [Learn
more about Healthy Hearing 2010]
References
Batshaw ML. Children with disabilities (4th edition).
Baltimore (MD): Paul H. Brookes Publishing Co.; 1997.
Kenneson A, Van Naarden Braun K, Boyle C. GJB2
(connexin 26) variants and nonsyndromic sensorineural hearing loss (HuGE
Review) [Web page]. August 2002 [cited 26 January 2004]. Available from:
URL:
http://www.cdc.gov/genomics/hugenet/reviews/GJB2.htm.
National Institute for Occupational Safety and Health. Hearing loss
prevention [Web page]. [cited 26 January 2004]. Available from: URL:
http://www.cdc.gov/niosh/topics/noise/default.html.
Steinberg A, Bain LJ. Hearing loss. In: Batshaw ML,
editor. When your child has a disability. Baltimore, (MD): Paul H. Brookes
Publishing Co.; 2001. p. 289-306.
Van Naarden K, Decouflé P. Relative and attributable
risks for moderate to profound bilateral sensorineural hearing impairment
associated with lower birth weight in children 3 to 10 years old.
Pediatrics 1999;104:905-10. [Read
a summary of this paper about birth weight and hearing loss]
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Screening
Hearing loss can affect a child’s potential to develop
speech, language, and social skills. The earlier a child who is deaf or
hard of hearing starts getting services, the more likely the child’s
speech, language, and social skills will reach their full potential.
All newborns should be screened for hearing loss. More
and more hospitals are screening babies before they go home. Universal
newborn hearing screening programs have three main goals:
-
Babies should be screened before they leave the
hospital or before 1 month of age.
-
If a baby does not pass the screening, he or she
should get a follow-up evaluation before 3 months.
-
Babies who are deaf or hard of hearing should receive
services before they are 6 months old. These services help babies develop
speech, language, and social skills.
CDC’s Early Hearing Detection and Intervention (EHDI)
program funds newborn hearing screening programs in many states. These
programs focus on developing surveillance and tracking systems and research
projects. The EHDI Web site covers topics such as screening guidelines,
state programs, and resources for parents and professionals. [Go
to the EHDI Web site] [Learn
about newborn hearing screening in your state]
Children should have their hearing tested again before
they enter school. Adults should have their hearing tested about once every
10 years between ages 18 and 50 years. After age 50, people should have
their hearing tested more often.
References
Batshaw ML. Children with disabilities (4th edition).
Baltimore (MD): Paul H. Brookes Publishing Co.; 1997.
Centers for Disease Control and Prevention. National EHDI goals
[Web page]. March 2004 [cited 11 May 2004]. Available from: URL:
http://www.cdc.gov/ncbddd/ehdi/nationalgoals.htm.
Healthy People 2010.
Chapter 28. Vision and hearing. Volume II (second edition) [Web page].
[cited 11 May 2004]. Available from: URL:
http://www.healthypeople.gov/document/HTML/Volume2/28Vision.htm.
National Institute on Deafness and Other Communication
Disorders.
What is Healthy Hearing 2010? [Web page]. October 2002 [cited 26 January
2004]. Available from: URL:
http://www.nidcd.nih.gov/health/healthyhearing/what_hh/objectives.asp.
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Date: October 29, 2004
Content source: National Center on Birth Defects and Developmental
Disabilities