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What is hearing loss?

Before we can understand hearing loss, we must first understand what hearing entails. When we hear sounds, we really are interpreting patterns of movement of air molecules. We can describe sounds in terms of their frequency (or pitch) and intensity (or loudness). Frequency is measured in hertz (Hz). A person who has hearing within the normal range, can hear sounds that have frequencies between 20 and 20,000 Hz. The most important sounds we hear every day are in the 250 to 6,000 Hz range. Speech includes a mix of low and high frequency sounds. Vowel sounds like “u” have low frequencies (250 to 1,000 Hz) and are usually easier to hear. Consonants like “s,” “h,” and “f” have higher frequencies (1,500 to 6,000 Hz) and are harder to hear. Consonants convey most of the meaning of what we say. Someone who cannot hear high-frequency sounds will have a hard time understanding speech.

Intensity, or loudness, is measured in decibels (dB). A person with hearing within the normal range can hear sounds ranging from 0 to 140 dB. A whisper is around 30 dB. Conversations are usually 45 to 50 dB. Sounds that are louder than 90 dB can be uncomfortable to hear. A loud rock concert might be as loud as 110 dB. Sounds that are 120 dB or louder can be painful and can result in temporary or permanent hearing loss.

Impairments in hearing can happen in either frequency or intensity, or both. Hearing loss severity is based on how well a person can hear the frequencies or intensities most often associated with speech. Severity can be described as mild, moderate, severe, or profound. The term “deaf” is sometimes used to describe someone who has an approximately 90 dB or greater hearing loss or who cannot use hearing to process speech and language information, even with the use of hearing aids. The term “hard of hearing” is sometimes used to describe people who have a less severe hearing loss than deafness.

Hearing loss can affect one or both ears. A loss that affects one ear is called a unilateral loss. A loss that affects both ears is called a bilateral loss.

There are four main types of hearing loss:

  • Conductive: Hearing loss caused by a problem in the outer ear or middle ear. Conductive losses usually affect all frequencies to the same degree. These losses are not usually severe.

  • Sensorineural: Hearing loss caused by a problem in the inner ear or auditory nerve. A sensorineural loss often affects a person’s ability to hear some frequencies more than others. This means that sounds may be appear distorted, even with the use of a hearing aid. Sensorineural losses can range from mild to profound.

  • Mixed: A combination of conductive and sensorineural losses.

  • Central: Hearing loss caused by a problem along the pathway from the inner ear to the auditory region of the brain or in the brain itself.

Approximately 30% of children who are deaf or hard of hearing also have one or more other developmental disabilities, such as mental retardation, cerebral palsy, vision impairment, or epilepsy. [Read more about developmental disabilities]

Hearing loss can affect a child’s ability to learn both to speak and to understand spoken language. This is especially true if the child is born with a hearing loss or loses his or her hearing before 2 years of age. People with hearing loss may communicate using speech (sometimes called oral communication), sign language (sometimes called manual communication), or a combination of both. Oral communication focuses on speech, listening with hearing aids, and sometimes lipreading. Manual communication includes sign language.

You can learn more about the following questions about hearing loss below:

  • How common is hearing loss?

  • What causes hearing loss? Can it be prevented?

  • What is the cost or economic impact associated with hearing loss?

  • What resources are available for people with hearing loss and their families?

  • How can we improve the health of people with hearing loss?

  • How can kids learn about hearing loss?

  • Where can I go to learn more about hearing loss?

We provide links to other Web pages if you want to learn even more about a topic. Some of these pages are within the CDC Web site and others are on outside Web sites. CDC has no control over the content on these outside sites.  Links to such sites are included for information only. The views and opinions expressed there are not necessarily those of CDC, the U.S. Department of Health and Human Services (HHS), or the U.S. Public Health Service (PHS).

References

Batshaw ML. Children with disabilities (4th edition). Baltimore (MD): Paul H. Brookes Publishing Co.; 1997.

National Dissemination Center for Children with Disabilities. Deafness and hearing loss [Web page]. January 2004 [cited 26 January 2004]. Available from: URL: http://www.nichcy.org/pubs/factshe/fs3txt.htm.

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.

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How common is hearing loss?

Photo of teacher and student signing in classroomIn the 20022003 school year, nearly 72,000 children ages 6 to 21 years got special education services under the “hearing impairment” category in the United States. Another 1,600 children received services under the “deaf blind" category. The total number of children with hearing loss is likely higher, since some of them may have other disabilities and be served under other special education categories. Still others may not be counted because they receive only regular education services.

CDC tracks the number of children in a five-county area in metropolitan Atlanta, Georgia who have  moderate to profound hearing loss in both ears. For this project, we define moderate to profound hearing loss as a 40 dB or greater loss in the better ear, without the use of hearing aids. This activity is part of the Metropolitan Atlanta Developmental Disabilities Surveillance Program (MADDSP). For 19911993, we found that, on average, about 9 in every 10,000 children ages 3 to 10 years had a moderate to profound hearing loss in both ears. Hearing loss was more common among older children than among younger children. Ninety percent of the children had a sensorineural hearing loss. Thirty percent of the children had one or more other disabilities in addition to their hearing loss. [[Read a summary of the article about hearing loss in MADDSP] [Read more about MADDSP]

CDC also studied hearing loss among children in metropolitan Atlanta in the mid-1980s. This project was done as part of the Metropolitan Atlanta Developmental Disabilities Study (MADDS), which studied how common certain disabilities were among 10-year-old children. The study found that 11 of every 10,000 children 10 years of age were deaf or hard of hearing. Hearing loss was slightly more common among boys than among girls. Twenty-eight percent of the children also had another disability, such as mental retardation, cerebral palsy, or epilepsy. [Read a summary of the article about hearing loss in MADDS] [Read more about MADDS]

In the 1988 National Health Interview Survey – Child Health Supplement, parents reported that that 3.5% of children ages birth to 17 years in the United States had ever had “deafness or trouble hearing” in one or both ears. [Read a summary of the paper about hearing loss in children in 1988]

Hearing loss is more common among older people than among children. In the 1994 National Health Interview Survey Core and Second Supplement on Aging, one third of adults ages 70 and older reported that they had trouble hearing. Seven percent reported that they were deaf in both ears and another 8% reported that they were deaf in one ear. Hearing loss was more common among men than among women. [Read the report on adult hearing loss]

References

Boyle CA, Decouflé P, Yeargin-Allsopp M. Prevalence and health impact of developmental disabilities in US children. Pediatrics 1994;93:399-403. [Read a summary of the paper about hearing loss in children in 1988]

Campbell VA, Crews JE, Moriarty DG, Zack MM, Blackman DK. Surveillance for sensory impairment, activity limitation, and health-related quality of life among older adults United States, 19931997. MMWR Surveillance Summaries 1999;48(SS-8):131-56. [Read this paper on adult hearing loss]

Drews CD, Yeargin-Allsopp M, Murphy CC, Decouflé P. Hearing impairment among 10-year-old children: metropolitan Atlanta, 1985 through 1987. American Journal of Public Health 1994;84:1164-66. [Read a summary of this MADDS paper]

U.S. Office of Special Education Programs. IDEA Part B child count (2002): Number served (ages 6-21), by disability and state. July 2003 [cited 26 January 2004]. Available from: URL: http://www.ideadata.org/tables26th/ar_aa3.htm.

Van Naarden K, Decouflé P, Caldwell K. Prevalence and characteristics of children with serious hearing impairment in metropolitan Atlanta, 19911993. Pediatrics 1999;103:570-5. [Read a summary of this MADDSP paper]

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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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What is the cost or economic impact associated with hearing loss?

Many people with hearing loss need long-term services. The average lifetime cost for one person with hearing loss is estimated to be $417,000 (in 2003 dollars). This represents costs over and above those experienced by a person who does not have a disability.

It is estimated that the lifetime costs for all people with hearing loss who were born in 2000 will total $2.1 billion (in 2003 dollars). These costs include both direct and indirect costs. Direct medical costs, such as doctor visits, prescription drugs, and inpatient hospital stays, make up 6% of these costs. Direct nonmedical expenses, such as home modifications and special education, make up 30% of the costs. Indirect costs, which include the value of lost wages when a person cannot work or is limited in the amount or type of work he or she can do, make up 63% of the costs.

These estimates do not include other expenses, such as hospital outpatient visits, sign language interpreters, and family out-of-pocket expenses. The actual economic costs of hearing loss are, therefore, even higher than what is reported here.

References

Centers for Disease Control and Prevention. Economic costs associated with mental retardation, cerebral palsy, hearing loss, and vision impairment --- United States, 2003. MMWR 2004;53:57-9. [Read this article on economic costs]

Honeycutt AA, Grosse SD, Dunlap LJ, Schendel DE, Chen H, Brann E, al Homsi G. Economic costs of mental retardation, cerebral palsy, hearing loss, and vision impairment. In: Altman BM, Barnartt SN, Hendershot GE, Larson SA, editors. Using survey data to study disability: results from the National Health Interview Survey on Disability. Research in social science and disability, volume 3. Amsterdam: Elsevier; 2003. p. 207-28.

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This page last updated Thursday, August 05, 2004

 


What is Hearing Loss?  |  How Common Is It?  |  Causes & Prevention  |  Screening  |   Economic Impact  |  Resources  |  Improving Health  |  Kids' Quest  |  Learn More  |  Contact Us


 

  

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The National Center on Birth Defects and Developmental Disabilities (NCBDDD) promotes the health of babies, children, and adults, and enhances the potential for full, productive living.  Our work includes identifying the causes of birth defects and developmental disabilities, helping children to develop and reach their full potential, and promoting health and well-being among people of all ages with disabilities.