Deafness and hearing loss

Key facts

• 360 million people worldwide have disabling hearing loss1.
• Hearing loss may result from genetic causes, complications at birth, certain infectious diseases, chronic ear infections, the use of particular 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 hearing aids, cochlear implants and other assistive devices; captioning and sign language; and other forms of educational and social support.
• Current production of hearing aids meets less than 10% of global need.

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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 40 decibels (dB) in the better hearing ear in adults and a hearing loss greater than 30 dB in the better hearing ear in children. The majority of people with disabling hearing loss 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 25 dB 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, cochlear implants and other assistive devices as well as captioning. 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

Congenital causes may 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 particular drugs during pregnancy, such as aminoglycosides, cytotoxic drugs, antimalarial drugs and diuretics;
• severe jaundice in the neonatal period, which can damage the hearing nerve in a newborn infant.

Acquired causes

Acquired causes may lead to hearing loss at any age, such as:

• infectious diseases such as meningitis, measles and mumps;
• chronic ear infections;
• collection of fluid in the ear (otitis media);
• use of particular drugs, such as some antibiotic and antimalarial medicines;
• injury to the head or ear;
• excessive noise, including occupational noise such as that from machinery and explosions, and recreational noise such as that from personal audio devices, concerts, nightclubs, bars and sporting events;
• ageing, in particular due to degeneration of sensory cells;
• wax or foreign bodies blocking the ear canal.

Among children, chronic otitis media is the leading cause of hearing loss.

Impact of hearing loss

Functional impact

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, he or she may feel excluded from social interaction.

Economic impact

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 about the needs of people with hearing loss, would decrease unemployment rates among this group.

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.

Prevention

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;
• following healthy ear care practices;
• screening of children for otitis media, followed by appropriate medical or surgical interventions;
• avoiding the use of particular drugs which may be harmful to hearing, unless prescribed and monitored by a qualified physician;
• referring infants at high risk, such as those with a family history of deafness or those born with low birth weight, birth asphyxia, jaundice or meningitis, for early assessment of hearing, prompt diagnosis and appropriate management, as required;
• reducing exposure (both occupational and recreational) to loud sounds by raising awareness about the risks; developing and enforcing relevant legislation; and encouraging individuals to use personal protective devices such as earplugs and noise-cancelling earphones and headphones.

Identification and management

Early detection and intervention are crucial to 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 is an effective tool for early identification and management of hearing loss.

People with hearing loss can benefit from the use of hearing devices, such as hearing aids, cochlear implants, and other assistive devices. They may also benefit from speech therapy, aural rehabilitation and other related services. However, global production of hearing aids meets less than 10% of global need and less than 3% of developing countries’ needs. The lack of availability of services for fitting and maintaining these devices, and the lack of batteries are also barriers in many low-income settings. Making properly-fitted, affordable hearing aids and cochlear implants 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.

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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.