Age and loud noises are the most common causes of hearing impairment.
Age-related hearing loss
Age is the biggest single cause of hearing impairment. Hearing impairment that develops as a result of getting older is often known as age-related hearing loss or presbycusis.
Most people begin to lose a small amount of their hearing when they are 30 to 40 years old. This hearing loss increases as you get older. By the age of 80 most people will have significant hearing impairment.
Age-related hearing loss occurs when the sensitive hair cells inside the cochlea gradually become damaged or die. As your hearing starts to deteriorate, high-frequency sounds, such as female or children’s voices, may become difficult to hear. It may also be harder to hear consonants, such as the letters s, t, k, p and f. This can make understanding speech in background noise very difficult.
Acoustic trauma
Another common cause of hearing loss is damage to the ear from loud noises. This is known as acoustic trauma and it can occur when part of the delicate inner structure of the ear becomes damaged. After prolonged exposure to loud noises, the cells inside the spiral part of the cochlea become inflamed.
The loudness of the noise and the length of time that you are exposed to it are important factors in acoustic trauma. If you are exposed to loud noises over a long period of time, you are more likely to develop acoustic trauma.
In particular, people who are at risk of developing acoustic trauma include those:
- who work with noisy equipment, such as pneumatic drills or compressed-air hammers
- who work in environments where there is loud music, such as nightclub staff
- who listen to music at a high volume through headphones
If you are at risk of developing acoustic trauma, you may want to read more about how to prevent hearing impairment.
Conductive hearing loss
Conductive hearing loss occurs when sounds are unable to pass into the inner ear. This is usually due to a blockage, such as having too much ear wax, or from a build-up of fluid caused by glue ear or an ear infection.
However, conductive hearing loss can also be caused by:
- a perforated eardrum – where the eardrum is torn or has a hole in it
- otosclerosis – an abnormal growth of bone in the middle ear which causes the inner hearing bone (the stapes) to be less mobile and less effective at transmitting sound
Sensorineural hearing loss
Sensorineural hearing loss occurs if the sensitive hair cells inside the cochlea (the coiled, spiral tube inside the inner ear) are damaged, or as a result of damage to the auditory nerve (the nerve that transmits sound to brain). In some cases, both may be damaged.
There are many different causes of sensorineural hearing loss, including:
- age-related hearing loss (presbycusis)
- genetic hearing loss – some people may be born deaf or become deaf over time due to a genetic abnormality, although there is not always a family history
- prolonged exposure to loud noises (acoustic trauma) which causes damage to the inner ear
- viral infections of the inner ear, such as mumps or measles
- viral infections of the auditory nerve, such as mumps or rubella
- Ménière's disease – where a person suffers with vertigo (spinning dizziness), hearing loss which can come and go, tinnitus and a feeling of blockage in the ear
- acoustic neuroma – a non-cancerous (benign) growth on or near the auditory nerve
- meningitis – an infection of the protective membranes that surround the brain and spinal cord
- encephalitis – inflammation (swelling) of the brain
- multiple sclerosis – a neurological condition that affects the central nervous system (the brain and spinal cord)
- stroke – where the blood supply to the brain is cut off or interrupted
Cytotoxic medication (chemotherapy), which is often used to treat cancer, and certain antibiotics such as Aminoglycosides can also damage the cochlea and the auditory nerve, causing sensorineural hearing loss.
