Hearing impairments are one of the most debilitating conditions in the world. Every year, more and more people are affected by disabling hearing loss, young and old alike.
According to hearing health estimates by the World Health Organization (WHO), hearing disabilities affect around 430 million people worldwide. That is roughly five percent of the global population.
While hearing loss is the main symptom, not all hearing impairments are the same. Numerous causes contribute to hearing loss, ranging from trauma to natural aging.
In this article, we look at all the different types of hearing loss, exploring what they mean and how these various impairments impact individuals.
What Is the Auditory System?
Before we explore the different types of hearing impairments, it’s important to take some time to understand the auditory system.
When people are hard of hearing, it is typically a result of a damaged or non-functioning auditory system.
In short, the auditory system helps convert sound waves. The main components include the outer ear, middle ear, inner ear, cochlea, auditory nerve, and many sub-components.
Common Symptoms of Hearing Loss
Some symptoms are common regardless of the type of hearing impairment or cause of hearing loss. These hearing loss symptoms include:
- Trouble hearing speech in environments with a lot of background noise.
- A constant need to increase the volume on TVs and other devices.
- Difficulties discerning which direction sounds are coming from.
- Issues hearing speech over the phone in noisy environments.
- A general muffling of speech or sounds.
- Tinnitus (ringing in the ear).
Four Types of Hearing Impairments
According to the Centers for Disease Control and Prevention (CDC), there are four types of hearing impairments or hearing loss:
- Sensorineural hearing loss
- Conductive hearing loss
- Mixed hearing loss
- Auditory Neuropathy Spectrum Disorder
Some of these categories of hearing loss can also have subcategories, which we will discuss.
For our purposes here, we will not look at deafness as its own hearing impairment type but rather as a degree of profound hearing loss.
Let’s take a closer look at these four types of hearing impairment.
What Is Sensorineural Hearing Loss?
The first type of hearing impairment is known as sensorineural hearing loss.
This type of hearing loss generally occurs when there is an issue with or damage to the components in the inner ear or nerve pathways, which is one common cause of hearing loss.
Typically, this involves damage to sensory cells — inner and outer hair cells. The two main causes of sensorineural hearing impairment are aging and exposure to loud noise.
Presbycusis
Sensorineural hearing loss due to aging is called age-related hearing loss or presbycusis.
According to hearing health data by the National Institute on Deafness and Other Communication Disorders (NIDCD), age is the strongest predictor of adult sensorineural hearing loss.
Age-related hearing loss affects about one in three older adults in the United States between the ages of 65 and 74. The number is half for those over the age of 74.
Noise-Induced Hearing Loss
Aside from natural aging, sensorineural hearing loss can also result from noise exposure.
Some risk factors include working in loud environments (factories or construction) or listening to music at high decibel levels.
The American Academy of Otolaryngology states that roughly 40 millions U.S. adults have noise-induced hearing loss. Noise-induced hearing loss can occur over time through long-term exposure or suddenly.
Sudden sensorineural hearing loss results from acoustic trauma from injury to the eardrum due to sudden exposure to loud sounds (like a gunshot, explosion, or machinery).
Due to the nature of this condition, sudden sensorineural hearing loss is considered a medical emergency and requires immediate medical attention.
This is why practicing good ear safety, like earplugs in noisy environments, is so important.
Other causes of sensorineural hearing loss:
- Ototoxic medications
- Ménière’s disease and autoimmune inner ear disease
- Benign tumors
- Meningitis
- Cochlear otosclerosis
What Is Conductive Hearing Loss?
Conductive hearing loss occurs when sound waves cannot pass through the ear canal and into the inner ear.
Sound is impeded somewhere within the outer or middle ear.
Causes of Conductive Hearing Loss
The main causes of conductive hearing loss include obstruction of the ear canal by a foreign body and trauma to the middle ear — usually to the ossicles.
Earwax impaction is another culprit. Earwax buildup (cerumen) can occlude sound from passing through to the middle ear.
Ear infections can do the same. Infections in the ear, like otitis media (middle ear infection) and Swimmer’s ear, cause fluid buildup and inflammation, preventing sounds from reaching the inner ear.
Other potential causes of conductive hearing loss:
- Eustachian tube dysfunction or blockage.
- Tympanic membrane perforation, also known as a ruptured eardrum.
- Stenosis, a narrowing of the ear canal.
- Abnormalities or deformities to the outer ear or ear canal.
- Cholesteatoma, an abnormal collection of skin cells inside the ear.
What Is Mixed Hearing Loss?
In some cases, a person can experience conductive hearing loss and sensorineural hearing loss simultaneously.
This is mixed hearing loss. So, rather than being its own condition, mixed hearing loss is a combination.
It can result from age-related hearing loss coupled with ear infections, noise-induced hearing loss, or earwax impaction.
What Is Auditory Neuropathy Spectrum Disorder?
The fourth type of hearing impairment is Auditory Neuropathy Spectrum Disorder (ANSD).
In short, this type of hearing loss occurs when the brain cannot organize sound normally. It is generally diagnosed in childhood.
Under normal hearing conditions, sounds get transmitted into electrical signals and sent to the brain to be processed. In the case of ANSD, these signals get jumbled along the way or don't reach the brain at all, leading to hearing problems.
Children with ANSD may have issues discriminating between sounds or understanding speech. The most likely cause of ANSD is damage to the auditory pathway. This can occur from head injuries, low birth weights, ototoxic medications, and hereditary factors.
Degree of Hearing Loss
According to the American Speech-Language-Hearing Association (ASHA), the degrees of hearing loss fall into three general categories: Mild, moderate, and severe.
Hearing loss is measured in units known as decibels (dB).
How Is Hearing Loss Diagnosed?
Hearing impairments are diagnosed by trained audiology professionals, like an ENT doctor or audiologist.
Hearing care specialists can perform audiometric tests (hearing tests) and interpret data audiograms to diagnose hearing impairments.
Treatment options for hearing impairments vary depending on the cause of the hearing loss. However, listening devices like hearing aids and cochlear implants are common treatment options.
Other treatment options, including ear wax removal or medications to treat serious ear infections, may be less invasive. Long-term treatments may also include speech-language therapy, learning sign language, or using language interpreters.
The Bottom Line
There are four main types of hearing impairments. Each type of hearing impairment has unique causes and requires different treatment options. If you’re experiencing hearing loss, consult an audiology professional who can help diagnose the exact cause of your hearing impairment, ensuring you get the best treatment plan that works for you.
Check out the USA Rx Hearing Loss Blog for more information on hearing loss and possible treatments.
References, Studies and Sources:
Deafness and hearing loss | WHO
Quick Statistics About Hearing | NIDCD | NIH
Block Out the Noise – American Academy of Otolaryngology-Head and Neck Surgery | AAO-HNS