Hearing impairment involves reduced (or severely reduced) hearing. This can be either temporary (e.g. due to fluid in the middle ear) or permanent. Hearing disorders can be classified by type (e.g. conductive hearing loss or sensorineural hearing loss) and by the severity of the hearing impairment. Hearing impairment can be acquired or inherited.

A Dutch study has shown that in approximately 40% of children born with a hearing impairment, the disorder is hereditary. In about 30% of the children, the hearing impairment is acquired (e.g. due to infections during pregnancy or lack of oxygen at birth). In another quarter it is not yet possible to establish the cause (about 7% can not be classified). However, hearing impairment can also occur at an older age, for example, as a result of meningitis, but also as a result of an hereditary disorder.

International publications show that about 1-3 newborn children per 1.000 have permanent hearing impairment of at least 40dB in both ears.

Severe hearing impairment at a young age can – if left untreated – result in impaired or severely impaired language and speech development. This in turn may lead to a limited or delayed development of intellectual potential, problems in social-emotional development, and reduced participation in social life. It is important to detect and treat hearing impairment in the first six months of life, as this has a favourable effect on communicative and linguistic development.

Depending on the severity of permanent hearing impairment, there are treatment options that enable language and speech development to proceed as favourably as possible. If there is sufficient residual hearing then hearing aids can be fitted, to amplify sounds. In hearing impaired people, sound is also often distorted, so they do not necessarily hear the same things with their hearing aids as those with normal hearing. If there is insufficient residual hearing, a hearing device that directly stimulates the auditory nerve can be surgically implanted (cochlear implant).

In young children with moderate to profound hearing impairment, family support is also used to stimulate the development of language and speech in the hearing impaired child and to help parents to bring up and support their child.