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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