The ageing process and loud noise are the most common causes of hearing loss.
Ageing
Getting older is the biggest single cause of hearing loss, and is referred to as age-related hearing loss or presbycusis. Most people begin to lose a small amount of their hearing when they are as young as in their 30s to 40s, and this increases as people grow older. By the age of 80, most people will have significant hearing problems.
Age-related hearing loss occurs when the sensitive hair cells inside the cochlea (the coiled, spiral tube section of the inner ear) gradually become damaged or die. This type of hearing loss is known as sensorineural hearing loss (see pics below).
As hearing starts to deteriorate, high-frequency sounds such as female or children’s voices may become difficult to hear. It can also be harder to hear consonants, such as the ‘f’ sound at the end of the word “tough” or the ‘s’ sound at the end of the word “pass”. This can make understanding speech in background noise quite difficult.
Loud noise
Another common cause of hearing difficulty is damage to the ear due to repeated exposure over time to loud noise. This is known as noise-induced hearing loss which occurs when the sensitive hair cells inside the cochlea become damaged and again this is known as sensorineural hearing loss.
Those who are at particular risk of developing noise-induced hearing loss include people who work with noisy equipment, such as pneumatic drills or compressed-air hammers; those who work in environments where there is loud music, such as nightclub staff, and people who regularly listen to music at high volume through headphones.
Healthy hair cells (left) and Damaged hair cells (right)
Images used with permission from Dangerous Decibels
Hearing loss can also happen suddenly due to an event where an exceptionally loud noise, such as an explosion or a rifle shot, occurs usually very close to the individual. This is known as acoustic trauma.
Other types of sensorineural hearing loss
Sensorineural hearing loss can be caused by:
- genetic hearing loss – whereby some people are born deaf or become deaf over time due to a genetic abnormality, although there is not always a family history of hearing loss;
- viral infections of the inner ear, caused by conditions such as mumps or measles;
- viral infections of the auditory nerve, such as mumps or rubella;
- Ménière’s disease – where a person suffers with episodes of vertigo (spinning dizziness), hearing loss which can come and go, tinnitus and a feeling of a blockage in the ear;
- acoustic neuroma – a non-cancerous (benign) growth on or near the auditory nerve;
- meningitis – an infection of protective membranes that surround the brain and spinal cord;
- encephalitis – inflammation of the brain;
- multiple sclerosis – a neurological condition affecting the central nervous system (the brain and spinal cord);
- stroke – where the blood supply to the brain is cut off or interrupted.
Some medications, such as some chemotherapy medicines and certain antibiotics can also damage the cochlea and the auditory nerve, causing sensorineural hearing loss.
Sensorineural hearing loss is generally permanent and hearing aids are often required to improve hearing in these cases.
Conductive hearing loss
Conductive hearing loss occurs when sounds are unable to pass into the inner ear, usually due to a blockage such as having too much or “occluding” ear wax, a build-up of fluid in the middle-ear (glue ear), or an ear infection.
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;
- damage to the hearing bones from injury, a collapsed ear drum or conditions such as cholesteatoma (an abnormal collection of skin cells inside the ear).
Comfortingly, conductive hearing loss is usually temporary and can often be treated with medication or minor surgery.