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.
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.
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]