Causes of hearing impairment and deafness

It is estimated that 50% of persons affected with hearing loss is not related to genetics, and that 50% of deafness is genetically inherited. If one or both parents or a relative is born deaf, there is a higher risk that a child will be born deaf. Statistics indicate that 70% of the population with a genetic cause of hearing loss have inherited a recessive gene. There are many genetic causes of hearing loss, but there are also many syndromes associated with hearing loss, the remaining 30%. While there are over 400 syndromes known to be associated with hearing loss, the following lists syndromes more commonly seen (and it is important to note that inheriting a syndrome does not always result in hearing loss).

Hearing impairment may also be caused by problems during pregnancy or at childbirth:

• 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
• jaundice, which can damage the hearing nerve in a newborn baby

Other causes of hearing impairment may include:

• 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.