Alphabetical Index Alphabetical Glossary

Deafness and hearing impairment


  • Hearing impairment is a broad term used to describe the loss of hearing in one or both ears. There are different levels of hearing impairment:
    • Hearing impairment refers to complete or partial loss of the ability to hear from one or both ears. The level of impairment can be mild, moderate, severe or profound;
    • Deafness refers to the complete loss of ability to hear from one or both ears.
  • There are two types of hearing impairment, defined according to where the problem occurs:
    • Conductive hearing impairment, which is a problem in the outer or middle ear. This type of hearing problem is often medically or surgically treatable, if there is access to the necessary services; childhood middle ear infection is the most common example;
    • Sensorineural hearing impairment, which is usually due to a problem with the inner ear, and occasionally with the hearing nerve going from there to the brain. This type of hearing problem is usually permanent and requires rehabilitation, such as with a hearing aid. Common causes are excessive noise and ageing.


  • According to 2005 estimates by the World Health Organization (WHO), 278 million people worldwide have moderate to profound hearing loss in both ears.
  • 80% of deaf and hearing-impaired people live in low- and middle-income countries.
  • The number of people worldwide with all levels of hearing impairment is rising mainly due to a growing global population and longer life expectancies.
  • Chronic middle ear infection is the main cause of mild to moderate hearing impairment in children.
  • The impact of hearing impairment on a child's speech, language, education and social integration depends on the level and type of hearing impairment, and the age of onset, especially if it begins before the age when speech normally develops.
  • In developing countries, fewer than 1 in 40 people who would benefit from a hearing aid have one.
  • Current annual production of hearing aids is estimated to meet less than 10% of global need.
  • 50% of deafness and hearing impairment is avoidable through prevention, early diagnosis, and management.


  • 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 before or during birth for several reasons. 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;
    • The use of ototoxic drugs - a group of more than 130 drugs (such as the antibiotic gentamicin) that can cause damage to the inner ear if incorrectly given - during pregnancy;
    • 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 cause damage to the cochlea (the hearing organ in 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 hearing impairment or deafness.


Hearing impairment and deafness are serious disabilities that can impose a heavy social and economic burden on individuals, families, communities and countries. Children with hearing impairment often experience delayed development of speech, language and cognitive skills, which may result in slow learning and difficulty progressing in school. In adults, hearing impairment and deafness often make it difficult to obtain, perform, and keep employment. Both children and adults may suffer from social stigmatization and isolation as a result of hearing impairment.

The burden of hearing impairment and deafness falls disproportionately on the poor, because they are unable to afford the preventive and routine care necessary to avoid hearing loss, or to afford hearing aids to make the condition manageable. Hearing impairment can also make it more difficult to escape poverty by slowing progress in school and the workplace, and placing people in social isolation.

The cost of special education and lost employment due to hearing impairment can also impose a substantial economic burden on countries.


  • Solutions to hearing impairment focus on prevention, early detection and management, and rehabilitation.
  • Many cases of sensorineural hearing impairment can be prevented through:
    • Immunizing children against childhood diseases, including measles, meningitis, rubella and mumps, according to national recommendations.
    • Immunizing women of child-bearing age against rubella before pregnancy.
    • Testing for 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.
    • Avoiding the effects of loud noise through reducing exposure (both occupational and recreational), using personal hearing protection and engineering noise control.
  • Many cases of conductive hearing impairment can be prevented from becoming chronic through appropriate detection, followed by appropriate medical or surgical interventions.
  • Early detection of and intervention against hearing impairment in babies and young children is essential to prevent problems in speech and language and in educational development.
  • Increased availability of affordable, properly fitted hearing aids and follow-up services can benefit many people with hearing impairment.


WHO activities for the prevention of deafness and hearing impairment assist countries to reduce and eventually eliminate avoidable hearing impairment and disability through appropriate preventive measures. These 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;
  • Developing a training resource on Primary Ear and Hearing Care for primary health care workers;
  • 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;
  • Encouraging countries to establish national programmes for prevention.


The hearing impairment and deafness control strategy is integrated into the overall WHO chronic disease prevention and control framework of the Department of Chronic Diseases and Health Promotion.

  • The strategic objectives of WHO's Department of Chronic Diseases and Health Promotion (CHP) are to advocate for health promotion and chronic disease prevention and control; promote health, especially for poor and disadvantaged populations; slow and reverse the adverse trends in the common chronic disease risk factors; and prevent premature deaths and avoidable disability due to major chronic diseases.
  • These strategic objectives are to be based on the following guiding principles: comprehensive and integrated public health action, intersectoral action, a life course perspective, and stepwise implementation based on local considerations and needs.

Sources: US Department of Health; The World Health Organization

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