An estimated 1.57 billion people worldwide experience some form of hearing loss, according to the Global Burden of Disease (GBD) study conducted in 2019, accounting for one in five people. Projections estimate that by 2050 the impact of hearing loss will reach between 2.35 and 2.56 billion people, a more than 56 percent increase from 2019.
The likelihood of you or someone near you experiencing hearing loss is steadily increasing due to a variety of lifestyle choices, social activities, and natural deterioration related to age. Because hearing loss can have a significant impact on your mental and physical health, relationships, and career, it’s important to develop a better understanding of it.
Warning Signs of Hearing Loss
To begin, here is a quick look at some of the warning signs that you or a loved one could be experiencing hearing loss, like:
- Muffled sounds and speech
- Difficulty understanding speech in a noisy environment
- Trouble distinguishing between the sounds of various letters (th, t, s, ch, etc.)
- Frequently asking people to repeat themselves
- Turning up the volume of the TV or radio
- Avoiding social events
- Irritability during conversations due to straining to understand
- Aural fullness or stuffiness
- Ringing in the ears (tinnitus)
If you or a loved one are experiencing one or several of these warning signs, it’s time to take a closer look at what causes hearing loss and begin looking for professional help.
How You Hear Sounds and Speech
Knowing how the process of hearing works is an important part of understanding what causes hearing loss. Here’s a quick look at how you’re able to hear sounds and speech.
There are three main parts along the hearing pathway: the outer ear, middle ear, and inner ear. The outer ear, or ear canal, conducts sound waves to the eardrum, causing it to vibrate.
The eardrum passes the vibrations it receives to three small bones located in the middle ear, which amplify these vibrations and pass them to the inner ear. In the inner ear, the vibrations pass through fluid into a snail-shaped part of the inner ear, known as the cochlea.
Within the cochlea, there are thousands of tiny, hairlike cells that receive the sound vibrations and convert them into electrical signals, which travel along the auditory nerve to the brain, where they are interpreted as recognizable sound.
The Three Types of Hearing Loss
In general, hearing loss involves an interruption of the process somewhere along the hearing pathway. The type and location of the interruption helps define the type of hearing loss.
There are three different types of hearing loss:
- Sensorineural hearing loss, the most common type of permanent hearing loss
- Conductive hearing loss, which can be temporary or permanent
- Mixed hearing loss, a combination of sensorineural and conductive hearing loss
Let’s examine the causes and symptoms of each of these types of hearing loss in greater detail.
Sensorineural Hearing Loss: Causes and Symptoms
Sensorineural hearing loss (SNHL), the most common type of permanent hearing loss, affects 85 to 90 percent of adults with hearing loss. It involves damage to the inner ear or the auditory nerve that transfers sound signals to the brain. Damage to the inner ear can be caused by a variety of conditions.
Presbycusis or Age-Associated Hearing Loss
Presbycusis is a progressive bilateral (both ears) type of SNHL that affects adults above 50 years of age. Presbycusis involves the degeneration of cochlear hair cells (stereocilia). Individuals with presbycusis usually experience slowly deteriorating hearing loss associated with a lack of clarity rather than a lack of volume, especially in the presence of background noise. Tinnitus often accompanies this form of SNHL.
Noise-Induced Hearing Loss (NIHL)
The second most common cause of hearing loss is noise-induced hearing loss, which occurs because of damage to the stereocilia inside the cochlea. NIHL can be caused by an extreme noise event like an explosion or due to ongoing exposure to sounds at an unsafe decibel level over an extended period of time.
NIHL affects individuals of all ages due to noise exposure in the workplace, from using certain power tools or lawn and garden equipment, from recreational activities (motorcycling, snowmobiling, hunting, shooting, etc.), or from social activities (concerts, major sporting events, nightclubs, personal listening devices, etc.).
The symptoms of NIHL are similar to those of presbycusis because it is essentially the same type of damage. NIHL is more often accompanied by tinnitus, and in many cases hyperacusis (moderate intensity sounds are perceived as abnormally loud) is also present.
Congenital sensorineural hearing loss is present at birth and is caused either by some genetic deformity or because of an illness during pregnancy. There are more than 400 syndromes that contribute to congenital SNHL, but only a small number of these account for the majority of cases:
– Waardenburg syndrome, the most common
– Usher syndrome
– Pendred syndrome
– Jervell and Lange-Nielsen syndrome
– Alport syndrome
Additional Causes of Sensorineural Hearing Loss
Though presbycusis, noise-induced hearing loss, and congenital hearing loss are the most common causes of SNHL, there are several other traumas or medical conditions that can cause damage to the inner ear, including:
– Head injuries
– Meniere’s disease
– Ototoxicity from medicines – aminoglycosides, loop diuretics, some chemotherapeutic agents
– Systemic conditions – meningitis, diabetes
– Vestibular schwannoma (also known as an acoustic neuroma)
– Others – autoimmune, barotrauma, perilymphatic fistula
Additional Signs and Symptoms of Sensorineural Hearing Loss
In addition to difficulties with hearing clarity, those experiencing SNHL may also begin to develop ringing in the ears (tinnitus), dizziness, balance disorders, and/or cognitive decline if the condition is left untreated.
Cause and Symptoms of Conductive Hearing Loss
Conductive hearing loss involves an obstruction or damage to structures at some point along the hearing pathway. The obstruction blocks the conduction of sound signals from reaching the inner ear. It can be temporary or permanent, depending on what causes the obstruction.
Different types of conductive hearing loss and the treatment options available for those experiencing them are characterized by the location of the obstruction and the cause of the obstruction.
Outer Ear Obstructions
Obstructions that occur in the outer ear typically include:
- Impacted earwax
- Stenosis or a narrowing of the ear canal
- Exostoses (bone-like protrusions inside the ear canal)
- Otitis externa (swimmer's ear)
- Obstructions caused by foreign bodies inserted into the ear
- Microtia or atresia (congenital deformity)
Middle Ear Obstructions
Middle ear obstructions can also interrupt conduction due to conditions like:
- Rupture of the tympanic membrane (eardrum)
- Tympanosclerosis (thickening of the tympanic membrane)
- Otitis media (an ear infection that produces fluid in the middle ear)
- Blockages in the Eustachian tube
- Otosclerosis (a middle ear disorder)
- Growths or tumours (cholesteatoma or glomus tumors)
- Ossicular chain discontinuity (a break in the connection of the middle ear bones due to injury)
Bonus Tip: Dealing With Earwax
One of the most common outer ear obstructions is built up or impacted earwax. Though impacted earwax may be related to many problems, attempting to remove it at home using cotton swabs and other devices is among the most common causes of impacted earwax.
Whenever possible, earwax removal should be conducted by a hearing care professional to prevent the wax from becoming impacted, avoid infections, and prevent damage to the ear canal or eardrum. If you must remove earwax at home, follow these steps:
- Place two to three drops of mineral or olive oil in one ear
- Lie sideways for approximately five minutes to allow for the oil to “sit and soak”
- Wipe any excess oil from the outside of your ear with a soft cloth
- Repeat on your other ear
- Continue this treatment for three to four days
Symptoms of Conductive Hearing Loss
The typical symptoms of conductive hearing loss involve loudness problems more than issues with clarity. Individuals with this type of hearing loss might turn up the volume on the TV or radio to improve hearing and might experience aural fullness or stuffiness, pain in and around the ears, tinnitus, or dizziness and vertigo.
Mixed Hearing Loss: Causes and Symptoms
Mixed hearing loss is less common than either of the other two types, affecting less than 2 percent of individuals with hearing loss. It is a combination of both sensorineural hearing loss and conductive hearing loss, and it can be bilateral (both ears) or unilateral (one ear).
There are only three instances in which mixed hearing loss occurs:
- An individual with sensorineural hearing loss is subjected to an injury, trauma, blockage, or illness
- that leads to the addition of conductive hearing loss
- Someone who already has conductive hearing loss sustains damage to the inner ear due to aging, NIHL,
- or some other cause that leads to the addition of sensorineural hearing loss
- A blast injury or other trauma causes simultaneous sensorineural and conductive hearing loss
Symptoms of Mixed Hearing Loss
The symptoms of mixed hearing loss depend on the severity of the issue. When examining mixed hearing loss symptoms, it’s best to attribute them to their respective type.
The sensorineural symptoms of mixed hearing loss can lead to:
Conductive hearing loss tends to have more “physical” symptoms, like:
- Pressure, pain, or “fullness” in one or both ears
- Strange odours or leakage from the ear canal
- Your voice sounding different to yourself
When left untreated, hearing loss can also cause a number of “side effect” symptoms, like irritability, stress, frustration, depression, mental exhaustion, and isolation.
A Hearing Assessment Is the First Step Toward Getting the Help You Need
Hearing loss not only affects your lifestyle and quality of life related to being able to hear well, but it can also lead to negative mental and physical health conditions when left untreated. As the prevalence of hearing loss continues to increase worldwide, getting ahead of this potentially destructive health problem is a major priority.
Whether your hearing assessment indicates that you have a hearing loss or not, the best prevention and treatment options to address hearing loss are far more effective with early detection, and each hearing assessment serves as a baseline against which future changes can be monitored. Audiologists advise that hearing assessments be every three to five years if you’re under the age of 50 and biennial (every two years) for individuals over the age of 50.