The Causes of Acquired Hearing Loss

The Causes of Acquired Hearing Loss

Hearing loss can affect people of all ages. While about 0.5% of babies born in the U.S. are born with a hearing loss, over 15% of Americans of all ages have hearing loss. This means the vast majority of hearing loss is acquired in the course of a person’s life. While age-related hearing loss (presbycusis) is the most common form of acquired hearing loss, it is by no means the only one.

Two Types of Hearing Loss

There are two main types of hearing loss: conductive and sensorineural. Conductive hearing loss is any type of hearing loss occurring in the outer or middle ear. Its causes can range from earwax blockage in the ear canal to broken ossicles (the three tiny bones in the middle ear) and more. The main defining feature of conductive hearing loss is that it is mechanical in nature. Many types of conductive hearing loss can heal or be surgically cured, which is not the case with sensorineural hearing loss.

Sensorineural hearing loss is the type of hearing loss we think of most often. It occurs most commonly in the inner ear, but also defines hearing loss as a result of abnormalities in the auditory nerves or in the brain itself. The most common type of sensorineural hearing loss involves the damage or death of the tiny, hair-like cells (cilia) which convert mechanical sound energy into electrical impulses inside the shell-shaped cochlea. Presbycusis is a type of sensorineural hearing loss, as is noise-induced hearing loss (NIHL).

Understanding the causes of acquired hearing loss can help us to determine whether the hearing loss may heal or be curable, and which treatments may be most effective.

Ear Infections

Infections of the middle ear (otitis media) are most common in children because the angle of their auditory tubes (formerly known as Eustachian tubes) is more horizontal, allowing pathogens to travel more easily to the tympanic cavity in the middle ear. In most cases, ear infections will subside on their own, but a trip to the pediatrician is suggested if the infection persists for more than a few days.

The primary symptom of an ear infection is pain in the ear. If the child doesn’t speak yet, you might be able to tell they have an ear infection if they are pulling or tugging on their ears, crying a lot, not responding to sound, sleeping less, have a fever, or if fluid drains from one or both ears.

Not all ear infections involve fluid, but when they do the filling of the tympanic cavity with this fluid can cause temporary deafness. Hearing ability nearly always returns when the infection subsides. If your child has frequent ear infections, an intervention such as “tubes in the ears” may be recommended to prevent potential permanent hearing loss. Hearing loss due to infections is conductive.

Ototoxic Medicines, Herbs and Chemicals

All in all, there are at least 1,000 substances known to cause hearing loss, tinnitus (ringing in the ears) or both. These include certain life-saving antibiotics and chemotherapies, some NSAIDS, some herbs (such as ginkgo biloba), chemicals found in workplaces, and many others. Your employer has a legal responsibility to make you aware of any ototoxic chemicals in the workplace.

If you are experiencing hearing loss or tinnitus, consult your doctor about any medications you’re on or herbal supplements you’re taking. While hearing loss from ototoxins is permanent, tinnitus may subside once exposure has ceased. Hearing loss due to ototoxic exposure is sensorineural.

Noise-Induced Hearing Loss (NIHL)

Many occupations present noise hazards. Factory floors are noisy and even classical musicians experience NIHL at a much higher rate than the general population. If you know you’re going to be exposed to loud noise, whether it’s at work or at play, be sure to wear hearing protection like earplugs or earmuffs, with a sufficient amount of protection for your environment.

Even exposure to non-painful noise levels over relatively short periods of time will cause permanent hearing loss. Sound levels reaching an average of 80 dBA can cause hearing loss after eight hours, with the time it takes for hearing loss to occur cut in half for every additional 3 dBA. This means that at 100 dBA, it only takes a few minutes for hearing loss to occur. If you think you might be exposed to excessive noise, consider downloading an SPL (sound pressure level) meter app on your smartphone. This will allow you to determine whether an environment is safe for the unprotected ear.

Illness and Injury

Diseases such as meningitis, encephalitis, measles, chicken pox, mumps and flu can leave us with hearing loss once other symptoms have subsided. Some people recovering from Covid-19 have reported persistent hearing loss months later.

Head injuries from sports, automobile accidents, falls, or any other cause are sometimes accompanied by hearing loss. Head trauma can cause conductive hearing loss or sensorineural hearing loss. Conductive hearing loss is common in cases of blunt trauma, especially when the blow comes on the ear itself.

The most common sensorineural hearing loss from head trauma is something called “hidden hearing loss,” where a person seems to have normal hearing according to a hearing test, but is unable to distinguish between sounds in a typical environment. This is because some head traumas, especially the kind of repeated, minor head traumas we experience in contact sports, can cause damage to the myelin sheaths surrounding the auditory nerves, allowing a lot of sonic information to “leak” out before it reaches the brain.

Hearing Aids Can Help

Whatever the cause may have been, if you’re having trouble hearing and a physician has determined that the best treatment is hearing aids, it’s best to start wearing them. Most people with mild to moderate hearing loss can maintain the lifestyle they’re used to by using hearing aids. Don’t let hearing loss determine the course of the rest of your life; make an appointment for a hearing test today.