Deafness and hearing loss
- 360 million people worldwide have disabling hearing loss1.
- Hearing loss may be inherited, caused by maternal rubella or complications at birth, certain infectious diseases such as meningitis, chronic ear infections, use of ototoxic drugs, exposure to excessive noise and ageing.
- Half of all cases of hearing loss are avoidable through primary prevention.
- People with hearing loss can benefit from devices such as hearing aids, assistive devices and cochlear implants, and from captioning, sign language training, educational and social support.
- Current production of hearing aids meets less than 10% of global need.
- WHO is assisting countries in developing programmes for primary ear and hearing care that are integrated into the primary health-care system of the country.
Over 5% of the world’s population – 360 million people – has disabling hearing loss (328 million adults and 32 million children). Disabling hearing loss refers to hearing loss greater than 40dB in the better hearing ear in adults and a hearing loss greater than 30dB in the better hearing ear in children. The majority of these people live in low- and middle-income countries.
Approximately one-third of people over 65 years of age are affected by disabling hearing loss. The prevalence in this age group is greatest in South Asia, Asia Pacific and sub-Saharan Africa.
Hearing loss and deafness
A person who is not able to hear as well as someone with normal hearing – hearing thresholds of 25dB or better in both ears – is said to have hearing loss. Hearing loss may be mild, moderate, severe or profound. It can affect one ear or both ears, and leads to difficulty in hearing conversational speech or loud sounds.
‘Hard of hearing’ refers to people with hearing loss ranging from mild to severe. They usually communicate through spoken language and can benefit from hearing aids, captioning and assistive listening devices. People with more significant hearing losses may benefit from cochlear implants.
‘Deaf’ people mostly have profound hearing loss, which implies very little or no hearing. They often use sign language for communication.
Causes of hearing loss and deafness
The causes of hearing loss and deafness can be divided into congenital causes and acquired causes.
Congenital causes lead to hearing loss being present at or acquired soon after birth. Hearing loss can be caused by hereditary and non-hereditary genetic factors or by certain complications during pregnancy and childbirth, including:
- maternal rubella, syphilis or certain other infections during pregnancy;
- low birth weight;
- birth asphyxia (a lack of oxygen at the time of birth);
- inappropriate use of ototoxic drugs (such as aminoglycosides, cytotoxic drugs, antimalarial drugs and diuretics) during pregnancy; and
- severe jaundice in the neonatal period, which can damage the hearing nerve in a newborn infant.
Acquired causes lead to hearing loss at any age.
- Infectious diseases such as meningitis, measles and mumps can lead to hearing loss, mostly in childhood, but also later in life.
- Chronic ear infection, which commonly presents as discharging ears, can lead to hearing loss. In certain cases this condition can also lead to serious, life-threatening complications, such as brain abscesses or meningitis.
- Collection of fluid in the ear (otitis media) can cause hearing loss.
- Use of ototoxic drugs at any age, such as some antibiotic and antimalarial medicines for example, can damage the inner ear.
- Head injury or injury to the ear can cause hearing loss.
- Excessive noise, including working with noisy machinery, and exposure to loud music or other loud noises, such as gunfire or explosions, can harm a person’s hearing.
- Age-related hearing loss (presbycusis) is caused by degeneration of sensory cells.
- Wax or foreign bodies blocking the ear canal can cause hearing loss at any age. Such hearing loss is usually mild and can be readily corrected.
Among children, chronic otitis media is the leading cause of hearing loss.
Impact of hearing loss
One of the main impacts of hearing loss is on the individual’s ability to communicate with others. Spoken language development is often delayed in children with deafness.
Hearing loss and ear diseases such as otitis media can have a significantly adverse effect on the academic performance of children. However, when opportunities are provided for people with hearing loss to communicate they can participate on an equal basis with others. The communication may be through spoken/ written language or through sign language.
Social and emotional impact
Limited access to services and exclusion from communication can have a significant impact on everyday life, causing feelings of loneliness, isolation and frustration, particularly among older people with hearing loss.
If a person with congenital deafness has not been given the opportunity to learn sign language as a child, they may feel excluded from social interaction.
In developing countries, children with hearing loss and deafness rarely receive any schooling. Adults with hearing loss also have a much higher unemployment rate. Among those who are employed, a higher percentage of people with hearing loss are in the lower grades of employment compared with the general workforce. Improving access to education and vocational rehabilitation services, and raising awareness especially among employers, would decrease unemployment rates among adults with hearing loss.
In addition to the economic impact of hearing loss at an individual level, hearing loss substantially affects social and economic development in communities and countries.
Half of all cases of hearing loss can be prevented through primary prevention. Some simple strategies for prevention include:
- immunizing children against childhood diseases, including measles, meningitis, rubella and mumps;
- immunizing adolescent girls and women of reproductive age against rubella before pregnancy;
- screening for and treating syphilis and other infections in pregnant women;
- improving antenatal and perinatal care, including promotion of safe childbirth;
- avoiding the use of ototoxic drugs, unless prescribed and monitored by a qualified physician;
- referring babies with high risk factors (such as those with a family history of deafness, those born with low birth weight, birth asphyxia, jaundice or meningitis) for early assessment of hearing, prompt diagnosis and appropriate management, as required; and
- reducing exposure (both occupational and recreational) to loud noises by creating awareness, using personal protective devices, and developing and implementing suitable legislation.
Hearing loss due to otitis media can be prevented by healthy ear and hearing care practices. It can be suitably dealt with through early detection, followed by appropriate medical or surgical interventions.
Identification and management
A large percentage of people living with hearing loss can benefit from early identification and intervention, and appropriate management.
Early detection and intervention is the most important factor in minimizing the impact of hearing loss on a child’s development and educational achievements. In infants and young children with hearing loss, early identification and management through infant hearing screening programmes can improve the linguistic and educational outcomes for the child. Children with deafness should be given the opportunity to learn sign language along with their families.
Pre-school, school and occupational screening for ear diseases and hearing loss can also be effective for early identification and management of hearing loss.
People with hearing loss can benefit from the use of hearing devices, such as hearing aids, assistive listening devices and cochlear implants. They may also benefit from speech therapy, aural rehabilitation and other related services. However, current production of hearing aids meets less than 10% of global need. In developing countries, fewer than one out of 40 people who need a hearing aid have one. The lack of availability of services for fitting and maintaining hearing aids, and the lack of batteries are also barriers in many low-income settings. Making properly-fitted, affordable hearing aids and providing accessible follow-up services in all parts of the world will benefit many people with hearing loss.
People who develop hearing loss can learn to communicate through development of lip-reading skills, use of written or printed text, and sign language. Teaching in sign language will benefit children with hearing loss, while provision of captioning and sign language interpretation on television will facilitate access to information.
Officially recognizing national sign languages and increasing the availability of sign language interpreters are important actions to improve access to sign language services. Human rights legislation and other protections can also help ensure better inclusion for people with hearing loss.
WHO assists Members States in developing programmes for primary ear and hearing care that are integrated into the primary health-care system of the country. WHO’s work includes:
- encouraging and guiding Member States in developing and implementing national plans for primary ear and hearing care;
- providing technical resources and guidance for training of health-care workers on primary ear and hearing care;
- developing and disseminating guidelines to address the major preventable causes of hearing loss;
- building partnerships to provide affordable hearing aids and services;
- raising awareness about the level, causes and impact of hearing loss as well as the opportunities for prevention, identification and management;
- collating data on deafness and hearing loss to demonstrate the scale and the impact of the problem; and
- promoting social inclusion of people with disabilities, including people with hearing loss and deafness, for example through community-based rehabilitation networks and programmes.
1 Disabling hearing loss refers to hearing loss greater than 40dB in the better hearing ear in adults and a hearing loss greater than 30dB in the better hearing ear in children.
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