Deafness and hearing impairment
Key facts
- In 2005, about 278 million people had moderate to profound hearing impairment. 80% of them live in low-and middle-income countries.
- Infectious diseases such as meningitis, measles, mumps and chronic ear infections can lead to hearing impairment. Other common causes include exposure to excessive noise, head and ear injury, ageing and the use of ototoxic drugs.
- Half of all cases of deafness and hearing impairment are avoidable through prevention, early diagnoses and management.
- Current production of hearing aids meets less than 10% of global need. In developing countries, fewer than 1 out of 40 people who need a hearing aid have one.
Types of hearing impairment
Deafness refers to the complete loss of hearing ability in one or two ears. Hearing impairment refers to both complete and partial loss of the ability to hear.
There are two types of hearing impairment, according to which part of the ear is affected. Conductive hearing impairment is a problem in the outer or middle ear. It is often medically or surgically treatable. A common example is chronic middle ear infection. Sensorineural hearing impairment is a problem with the inner ear, or, occasionally with the hearing nerve. It is usually permanent and requires rehabilitation such as the use of a hearing aid. Sensorineural hearing impairment is commonly due to excessive noise, ageing and infectious diseases such as meningitis, measles rubella and mumps.
Causes of hearing impairment and deafness
Deafness can be inherited. If one or both parents or a relative is born deaf, there is a higher risk that a child will be born deaf.
Hearing impairment may also be caused by problems during pregnancy and childbirth. These include:
- premature birth;
- conditions during birth in which a baby lacks enough oxygen to breathe;
- rubella, syphilis or certain other infections in a woman during pregnancy;
- inappropriate use of ototoxic drugs (a group of more than 130 drugs, such as the antibiotic gentamicin) during pregnancy; and
- jaundice, which can damage the hearing nerve in a newborn baby.
Infectious diseases such as meningitis, measles, mumps and chronic ear infections can lead to hearing impairment, mostly in childhood, but also later in life. The use of ototoxic drugs at any age, including some antibiotic and anti-malarial drugs, can damage the inner ear. Head injury or injury to the ear can cause hearing impairment.
Wax or foreign bodies blocking the ear canal can cause hearing loss at any age. Excessive noise, including working with noisy machinery, exposure to loud music or other loud noises, such as gunfire or explosions, can damage the inner ear and weaken hearing ability. As people age, accumulated exposure to noise and other factors may lead to deafness or hearing impairment.
Social and economic burden
Hearing impairment can impose a heavy social and economic burden on individuals, families, communities and countries.
Hearing impairment in children may delay development of language and cognitive skills, which may hinder progress in school. In adults, hearing impairment often makes it difficult to obtain, perform, and keep jobs. Hearing impaired children and adults are often stigmatized and socially isolated.
The poor suffer more from hearing impairment because they cannot afford the preventive and routine care to avoid hearing loss nor the hearing aids to make the disability manageable. Hearing impairment also makes it more difficult for them to escape poverty by hindering progress in school or in the workplace and by isolating them socially.
For countries, the cost of special education and lost employment due to hearing impairment can burden the economy.
Prevention
Solutions to hearing impairment focus on prevention, early detection and management, and rehabilitation.
Sensorineural hearing impairment can be prevented by:
- immunizing children against childhood diseases, including measles, meningitis, rubella and mumps;
- immunizing women of child-bearing age against rubella before pregnancy;
- screening and treating syphilis and certain other infections in pregnant women;
- improving antenatal and perinatal care;
- avoiding the use of ototoxic drugs unless prescribed by a qualified health care worker and properly monitored for correct dosage;
- referring jaundiced babies for diagnosis and possible treatment;
- reducing exposure (both occupational and recreational) to loud noises by using personal protective devices and by engineering noise control.
Conductive hearing impairment can be prevented through early detection, followed by appropriate medical or surgical interventions.
In babies and young children, early detection and treatment prevents problems with language development and progress in school.
Making affordable and properly fitted hearing aids and follow-up services more available can benefit hearing impaired people.
WHO activities
WHO assists Members States in reducing and eventually eliminating avoidable hearing impairment and deafness through preventive and rehabilitative measures that include:
- developing a global database on deafness and hearing impairment to demonstrate the size and costs of the problem and help compare cost-effectiveness of interventions;
- training primary health care workers on ear and hearing care;
- developing and disseminating guidelines against major preventable causes of hearing impairment;
- building partnerships to provide affordable hearing aids and services to people in need;
- raising awareness about the level and costs of hearing impairment and the opportunities for prevention; and
- encouraging countries to establish national prevention programmes.
For more information contact
WHO Media centre
Telephone: +41 22 791 2222
E-mail: mediainquiries@who.int