Understanding Hearing Loss and Deafness

The meaning of 'hearing loss' sounds obvious.

However, it also has a specific meaning in healthcare (see box).

Defining deafness, hearing loss and disabling hearing loss

deaf, adj. dull of hearing, unable to hear at all, deafness, n. Chambers English Dictionary, 1988 edition.

"A person who is not able to hear as well as someone with normal hearing - hearing thresholds of 20 dB [decibels] or better in both ears - is said to have hearing loss." World Health Organization, Deafness and hearing loss

"Disabling hearing loss refers to hearing loss greater than 35 decibels (dB) in the better hearing ear." World Health Organization, Deafness and hearing loss.

Hearing loss is therefore any inability to hear as well as is considered 'normal'. It may occur to various degrees, usually classified as mild, moderate, severe and profound:

People with mild hearing loss may hear most speech, but not someone talking softly;
People with moderate hearing loss will usually find it hard to hear someone talking at a 'normal' level;
People with severe hearing loss will generally only hear loud sounds;
People with profound hearing loss will hear no speech, and probably only very loud sounds.

The term deafness is generally used for profound hearing loss.

Hearing loss may also occur in one or both ears, and differently in each ear. It may stay the same, get worse, fluctuate, or get better, depending on the cause.

The World Health Organization estimates that by 2050, around 2.5 billion people in the world will have some level of hearing loss. More than 700 million will need some kind of hearing support like hearing aids to help with disabling hearing loss. This amounts to one in every 10 people around the world.

Hearing loss is therefore a massive issue.

Types of Hearing Loss

The UK's Royal National Institute for Deaf People (RNID) states that both hearing loss and deafness happen when sound signals do not reach the brain.

It is worth understanding more about how hearing works (see box).

How hearing works

The diagram below shows the ear, and how it is divided into three parts: outer, middle and inner ear.

Sound waves are picked up by the pinna, the visible bit of the ear. This amplifies them and channels them into the ear canal until they meet the ear drum. They cause the ear drum to vibrate at the frequency of the sound wave. The movement of the ear drum causes movement in three small bones called ossicles, just inside the middle ear. As the ossicles move, they transmit the movement of the ear drum onwards, to the inner ear and particularly to the cochlea (the snail-shaped organ in the picture). This contains fluid that moves with the vibrations from the ear drum and ossicles.

As the fluid moves, it moves nerve endings, sometimes called hairs. These are part of the auditory nerve, which sends electrical signals to the brain. When those signals reach the brain, it interprets them into the noises that we hear.

There are two main ways in which the sound waves getting to the brain may be disrupted. This results in three main types of hearing loss:

Sensorineural hearing loss is caused by damage to the hair cells in the cochlea, or to the auditory nerve. This type of hearing loss is usually permanent.
Conductive hearing loss is caused by something stopping the sound from passing through the outer or middle ear, such as ear wax or an ear infection. This type of hearing loss is usually temporary.
Mixed hearing loss is a combination of the two.

There is also a fourth type of hearing loss, known as auditory neuropathy spectrum disorder. This occurs when sound enters and passes through the ear normally, but the brain cannot interpret it correctly. Interestingly, people with auditory neuropathy often perform fairly well on standard hearing tests involving bleeps. However, they almost always have difficulty interpreting speech.

Causes of Hearing Loss

The most common cause of hearing loss is simply the changes that happen over time.

This gradual age-related hearing loss is known as presbycusis. It tends to affect both ears, and gets worse as you get older. It is basically a matter of 'wear and tear' on your ears, especially the hairs in your cochlea. People tend to 'lose' higher pitched sounds first, and lower sounds later, and hearing aids often help.

Some people find that they have sudden hearing loss: that is, they lose their hearing suddenly. This might be due to an ear infection or ear wax. However, it could also be something more sinister such as a tumour. Sudden hearing loss should therefore always be investigated.

The second most important cause of hearing loss is being exposed to loud noises.

This can be a single very loud noise like a gunshot or explosion, or noise over a long period of time. This includes machinery such as on a factory floor or other industrial setting. Health and safety laws have helped significantly with that, although they are not consistently in place or applied around the world. However, it also includes listening to music via headphones or in clubs or concerts.

The World Health Organization states that over 1 billion young people are at risk of what it describes as "permanent, avoidable hearing loss" because of unsafe listening practices.

There are also other causes of hearing loss, including:

Genetic hearing loss. This may be associated with other conditions, or occur as a stand-alone condition. Most of the genes known to be associated with hearing loss affect children and young people. However, it is also possible that age-related hearing loss may be at least partly influenced by genetic factors.
Exposure to certain medicines, known as ototoxic medications. For example, Cisplatin, a chemotherapy agent, has a known side-effect of causing tinnitus, or noises in the ear that disrupt ability to hear. Some medicines can also affect balance, which is controlled by the inner ear.
Exposure to certain viruses in utero such as rubella or cytomegalovirus, or certain conditions as a baby, such as severe jaundice in the period immediately after birth.

Effects of Hearing Loss

One of the biggest problems with hearing loss is that it affects ability to communicate.

It therefore makes life hard, because you cannot hear what is going on around you. Adults with hearing loss often report feeling more isolated, or even depressed. Hearing loss is also linked to risk of falling. This is probably because it is associated with damage to the inner ear, which also contains the body's balance organs.

Finally, hearing loss may also be associated with loss of ability to think, a condition called cognitive impairment. It is not clear why this happens.

Treating Hearing Loss

One of the most effective ways of treating hearing loss is to prevent it from happening in the first place (see box).

Preventing hearing loss

Many of the global cases of hearing loss are preventable. Strategies for preventing hearing loss include:

Widespread vaccination campaigns against conditions like rubella and measles;
Good genetic counselling to ensure that people understand the chances of having a child with hearing loss;
Good maternal and neonatal healthcare;
Better children's healthcare to ensure that ear conditions are recognised and managed appropriately, for example, by screening babies' hearing;
Better health and safety practices to reduce exposure to loud noises at work;
Education to promote safer listening practices at home; and
Better use of medicines to prevent ototoxic hearing loss.

The treatment of temporary hearing loss will depend on its cause.

For example, ear wax may be treated by syringing the ears. Ear infections might require antibiotics. Ototoxic hearing loss may be treated by reducing the dose, or changing the medication.

Once permanent hearing loss has occurred, there are various possible treatments.

The starting point is often the use of hearing aids or other hearing technologies, such as cochlear implants. However, people with hearing loss may also benefit from speech therapy to improve their other communication abilities.

People with profound hearing loss may learn to communicate through sign language or other sensory substitution. Lipreading may also be helpful, although it has its limitations.

Finally, therapy may be helpful to enable people with hearing loss to manage the psychological impacts of their condition.

Living with Hearing Loss

Even with assistive technology such as hearing aids, communication may remain more difficult for those with hearing loss. It may be improved by:

Reducing background noise. For example, move away from busy areas if you need to speak to someone.
Wearing ear protection if you are still exposed to loud noises, for example at work.
Facing people when they are talking to you, and asking them to look at your when they are talking. This will help you to see mouth movements, and also pick up on body language and facial expressions.
Asking people to repeat themselves, or write things down. This may seem embarrassing, but it is better than failing to understand, especially in important situations like doctors' appointments.
Avoiding listening to loud music. Instead, keep the volume so that you can hear it comfortably.
Not putting anything in your ears, including your fingers, especially if your ears feel blocked.

And Finally...

Hearing loss can be debilitating, but it is also often avoidable.

Small actions like not listening to very loud music, or wearing ear protection at work, may make a big difference later in your life. However, if you do have hearing loss, you can also take steps to make it easier to manage, especially by changing how you communicate with others in quite small ways.

Continue to:
Avoiding Common Communication Mistakes
Speech and Language Disorders