Hearing Loss: Invisible and Insidious!

When it comes to health and wellbeing, hearing health is probably one of most ignored domains and often misunderstood. Hearing loss, even if significant, can often be attributed to the issue with speaker’s way of talking rather than a declivity of own’s hearing (only if they can talk to me looking directly towards me, only if they talk to me clearly).

It is often misunderstood because the one of the most common reasons one may think of hearing loss is earwax (cerumen) yet the culprit most of the time is not the humble earwax (protecting your ear canal from infections and foreign bodies) but physiological changes occurring at the level of inner ear (ever heard of hair cells?). Mind you, this is not to say that earwax may not be a cause, but even a significant build-up would likely only cause hearing loss on complete earwax occlusion of ear canal.

Now we have spoken on earwax in outer ear, and we spoke about physiological changes in inner ear, but this crude explanation of ear system will be incomplete without mentioning the part connecting the outer ear to inner ear, the middle ear (no guesses with the name of course). If you have ever wondered what the smallest bone in our body could be and where it may be, look no further than your middle ear. The middle ear in simple terms, act as a funnel with a piston transmitting vibrations of the eardrum (tympanic membrane) through three little bones onto the inner ear (cochlea).

The littlest of these little bones is Stapes, also the smallest bone in our body. Hearing loss which occurs due to any condition which affects the conduction of mechanical vibrations through the outer or middle ear is called conductive hearing loss. However, any problem at the level of inner ear (cochlea), our sensory organ of hearing is called sensorineural hearing loss. And hearing loss can also be due to the combination of conductive hearing loss and sensorineural hearing loss, which is then called mixed hearing loss (no guesses with the name again).

Although hearing loss and its effects are being talked about at present more than ever before, there is still overall lack of understanding of hearing loss, what causes hearing loss and factors which affect hearing loss diagnosis and management.

Probably the most common cause of hearing loss which we are familiar with is the loss of hearing with age, however the onset and progression of hearing loss varies from individual to individual and is often affected with environmental factors such as excessive noise exposure, genetic predisposition etc. However, there are several other presentations of hearing loss, for example hearing loss present in newborn babies from birth as well as hearing loss caused due to certain genetic conditions and exposures to certain ototoxic agents which may cause permanent damage to inner ear.

Prevalence of hearing loss?

According to Department of Health and Aged Care, in Australia, about 3.6 million people have some level of hearing loss with more than 1.3 million people live with a hearing condition that could have been prevented and more than 1 in 3 Australians have noise-related ear damage. As Australia’s population ages, the number of people with a hearing impairment to double to an estimated 7.8 million people in 2060.

The Aboriginal and Torres Strait Islander children have a much higher rate of ear disease than other children, which can result in hearing loss.

Hearing loss affects all ages, genders, races, and ethnicities. Hearing loss is common in older adults and this age related hearing loss is called presbycusis. Hearing loss increases from about half of those aged 60 to 70, to 70% of those aged 70 and over, and 80% of those aged 80 (data from Department of Health and Aged Care).

Hearing loss also affects infants and children. Hearing loss in children is one of the most common birth defects. A condition that is present at birth is called a congenital condition.

What are the types of hearing loss?

Hearing loss can impact hearing in one ear or both ears and in different degrees. If the hearing loss only affects one ear, it is considered unilateral hearing loss and if both ears are involved it is called bilateral hearing loss. Also, if the hearing loss is of the similar degree in each ear, it is called symmetrical hearing loss and if hearing loss in one ear varies from the other ear, it is called asymmetrical hearing loss.

We already spoke about types of hearing loss earlier; however, it may be worthwhile to mention it again here. As such the types of hearing loss include the following:

• Conductive Hearing Loss: It involves outer or middle ear and is caused due to sound vibration obstruction as it passes through the outer ear (ear canal) or middle ear. The block may be an ear infection, earwax or fluid in the ear or any condition which affects the mechanics of the middle ear system such as stiffness in the bones of middle ear or significant negative middle ear pressure.
• Sensorineural Hearing Loss: Hearing loss affects the inner ear (cochlea) and the tiny hair cells lining the cochlea or auditory nerve. Aging and loud noise can cause wear and tear on the hairs or nerve cells in the cochlea that send sound signals to the brain. The damaged hair cells are unable to send signal through to the brain and this causes hearing loss. Children are prone to this type due to congenital conditions (present at birth), trauma during childbirth, head injuries or infections. Sensorineural hearing loss is often permanent. 
• Mixed Hearing Loss: Hearing loss which is caused with combination of both conductive element as well as sensorineural element is called mixed hearing loss.

Hearing Loss can be deceptive!

A person developing hearing loss gradually, particularly in early stages, may be able to compensate well for missing information easily through contextual cues as well as visual cues and still manage to communicate.

Even in later stages of hearing loss, audibility of several environmental sounds and audibility of the voice may be retained.

When the hearing loss progresses to the stage where common environmental sounds as well as speech is not audible at all, and the person hear very little or nothing at all and often reflects a severe to profound degree of hearing loss. 

Hearing loss even in early stages have been shown to exert strain on cognitive resources. Additionally, the auditory system experiences deprivation of auditory stimulus which over time can be regressing for the health of auditory system. Therefore, it is important to assess hearing as part of the regular health checks.