/ / What Is Hearing Loss Caused By?

What Is Hearing Loss Caused By?


The World Health Organization predicts that by 2050, every fourth person will experience hearing loss. That is a lot of people! If we want to prevent hearing loss, we need to know what causes it. This article will discuss hearing loss causes and why they are on the rise.

Hearing Loss Causes

There are many causes of hearing loss, and human beings are more vulnerable to hearing loss in the womb, in childhood, and in old age.

However, throughout life, hearing loss can occur due to various factors. These factors can include:

hearing loss caused by age
  • Infections
  • Genetic causes
  • Ototoxins
  • Noise exposure
  • Chronic conditions
  • Autoimmune conditions.

Causes of Hearing Loss During Prenatal Period

What causes hearing loss? Hearing loss causes change during various stages of life. The prenatal period is crucial for fetal development. During this time, the baby’s nervous system is still being formed. Any variations in the genetic code can affect the development of vital organs.

Genetic Causes

The most common cause of prenatal hearing loss is genetic conditions. Many of them are non-syndromic, and that is, they are not associated with a syndrome. The genetic causes can either be a familiar issue that is hereditary or a one-off non-hereditary mutation.

20% of genetic conditions are caused by syndromic conditions like Waardenburg syndrome, Ushers syndrome, and Pendred syndrome. In cases of syndromic causes, many other symptoms are seen.  60% of all genetic conditions are associated with mutations in the GJB2 and/or GJB6 genes.

These conditions could be dominant, recessive, or mitochondrial genetic causes. The list of genetic causes is extensive.

Infectious Causes

Infections during the prenatal period are also dangerous for the growing fetus. While TORCHES (Toxoplasma, rubella, CMV, Herpes, and Syphilis) are more common in developing countries, one must be vigilant regarding these infections, as they can cause permanent hearing loss.

During the prenatal period, unsafe sex, low immunity, and STDs can cause intrauterine infections that lead to hearing loss. These primarily affect the middle ear and the ear canal.

Hearing Loss During Perinatal Period

The perinatal period lasts up to a year until birth. The birth process itself can cause hearing loss if it is traumatic in any way. Some studies have proven the effect on hearing, while other studies are still investigating the causes.

Hypoxia and Hearing Loss

One hypothesis cause is hypoxia or the lack of oxygen to the baby around birth. A lack of oxygen could be due to various reasons, including cord compression, the nuchal cord, head compression, the compromised blood supply to the placenta, or premature rupture of the membranes. The list is endless.

Some scientists suggest that a lack of oxygen can cause hearing loss, and there is debate about whether or not acute or chronic injuries cause hearing loss. However, a lack of oxygen can affect hearing especially when the blood-inner ear barrier is inadequate in newborns.

Hyperbilirubinemia

Newborns with jaundice tend to have hearing problems. Bilirubin is ototoxic, and high bilirubin levels can be deposited into the brain stem and damage which can also damage the auditory nerve.

Low Birth Weight

Children with low birth weights can have sensorineural hearing loss. Similarly, preterm babies can have some degree of hearing loss, and the reason for this is that their ears are not fully developed in preterm.

Infections

Persistent and untreated TORCHES infections also cause hearing loss. Rubella causes about 60% of all hearing loss among TORCHES infections.

Deafness also develops as a complication from meningitis. This could be viral or bacterial. It is one of the significant causes of hearing loss and manifests in the early stages of meningitis. It can also lead to deafness if not treated promptly.

Mumps is a common cause of unilateral, sudden hearing loss. It is postulated that this occurs via infection of the endolymph.

Diabetes

Children who have inherited maternal diabetes have hearing loss due to auditory nerve damage, and doctors are not sure why and how this happens.

Alcohol

alcohol causes hearing loss

Alcohol alters the composition of inner ear fluid so that it can cause hearing loss. In children exposed to alcohol, hearing impairment is observed, and this is also seen in adults as “cocktail deafness” in people who binge drink.

Drugs

Many drugs and medications can cause deafness in children. The common culprits are antibiotics like gentamicin, and antibiotics can damage the ears’ inner hair cells, leading to hearing loss. A hearing aid does not help in this case unless the drug is discontinued.

Causes of Hearing Loss Among Children and Teenagers

There are other causes for hearing loss in children and teenagers, outside of early childhood causes.

Infections

A significant cause of conductive hearing loss is recurrent ear infections. Examples of such infections are chronic suppurative otitis media and fluid collections in the ear, or chronic nonsuppurative otitis media, damaging the tympanic membrane.

Sound waves are transmitted across the tympanic membrane, and these damaged eardrums can be repaired via surgery. For this reason, middle ear infections must be treated promptly.

Trauma

Head injuries and traumatic ear injuries can damage the outer ear, which affects hearing. Traumatic brain injuries involving the auditory cortex can also affect how sound is processed, leading to hearing impairment.

Smoking Tobacco

smoking tobacco causes hearing loss

Secondhand smoke is just as dangerous as smoking. Smoking among teenagers is discouraged because cigarette smoke contains harmful substances that are ototoxic. The same secondhand smoke can affect young children’s ears as well. Additionally, nicotine affects the blood supply to the ears.

Noise

Noise exposure over a prolonged period causes noise-induced hearing loss. More teenagers are now experiencing hearing loss with one in five, and these numbers are projected to increase.

Since more people use headphones to listen to media via their smartphones and tablets without set breaks, this affects normal hearing.

This constant noise exposure damages the outer hair cells. This, plus other loud noises like traffic, concerts, games, and theatres, and the exposure is a barrage of noise that is slowly damaging the ear.

Causes of Hearing Loss During Adulthood

For adults, there are many causes of hearing loss. Injury to the ear, severe head injuries, exposure to loud noise/loud music/loud sounds, blocked ear wax, and foreign bodies are among some of them.

Medications

There are over 700 ototoxic medications. Taking them as part of your healthcare practice can result in hearing loss and auditory symptoms.

However, you cannot avoid them. Some of these medicines are lifesaving anti-cancer drugs, analgesics, or antibiotics, and the benefits outweigh the side effects. If you are taking ototoxic drugs, talk to your health care provider about alternatives.

Environmental Toxins

environmental toxins cause hearing loss

We come across industrial chemicals throughout our lifetime. At work, on-site, or even everyday household supplies contain ototoxic chemicals, and we often know little about them.

They are omniscient in the form of our varnishes, printing inks, polishes, paints, and cleaning solvents; the list goes on. You may recognize some of them as styrene, carbon disulfide, toluene, and xylene.

These are commonly identified as ototoxic chemicals. There is also lead and mercury, elements that also affect hearing in addition to causing many other side effects.

If possible, look for substances that do not have these chemicals or wear ear and face protection when using these substances.

Nutritional Deficiencies

Studies show that vitamins A, B, C, and E’s nutritional deficiencies can cause hearing loss. Vitamins are essential to building immunity. Without them, it is hard to stave off infections that affect the ear, making you more vulnerable to them.

Mineral deficiencies of zinc, magnesium, selenium, iron, and iodine can also affect hearing. These minerals are cofactors of various immune reactions within the body.

Infections

Viral infections like Varicella, Mumps, and Rubella can invade the cochlea and cause hearing loss. Similarly, West Nile virus, HIV, rubella, and CMV are implicated in hearing loss to some extent.

Most of them are responsible for sensorineural hearing loss, but some cause mixed hearing loss as well. These viral infections are primarily seen in immunocompromised adults.

Geriatric Causes of Hearing Loss

Hearing loss is most prevalent in the geriatric population, and part of the reason is a gradual degeneration of the ears.

Presbycusis

Age-related sensorineural degeneration (presbycusis) is most commonly referred to as age-related hearing loss. The cochlea, inner ear, and the rest of the auditory pathway, with time, break down due to age which leads to hearing loss.

The best way to limit hearing loss due to presbycusis is by wearing ear protection, staying away from noise, and refraining from smoking tobacco limits presbycusis. Hearing aids may also help prevent symptoms from worsening.

Chronic Conditions

Alzheimers can cause hearing loss

Various chronic diseases like diabetes, Alzheimer’s, and depression affect hearing. Diabetic neuropathy is responsible for hearing loss.

High levels of sugar cause microscopic damage to the blood vessels supplying the ears. With time, these injuries build up, and without an adequate blood supply, the ear is affected, leading to hearing loss.

When it comes to Alzheimer’s, there is an ongoing debate on whether hearing loss causes Alzheimer’s or vice versa?

The connection is proven, but how it happens is still not understood. As the brain shrinks, the brain loses the auditory cortex, which processes hearing. So, hearing loss ensues with a loss of brain tissue.

It has also been observed that without hearing, cognitive development stalls, and hearing contributes to keeping the brain active.

People with hearing loss have depression. However, a few studies have suggested bidirectionality in this area, which means that depression can potentiate hearing loss. Studies have shown that depressed people have high rates of sensorineural hearing loss.

Autoimmune Conditions

Various autoimmune conditions that cause hearing loss include the AIED (an autoimmune inner ear disease). These are immune disorders where the body attacks itself, especially in systemic inflammatory disorders (SAD). They include Scleroderma, Wegener’s granulomatosis, and SLE.  

In most cases, the hearing loss is bilateral, sensorineural, and progresses quickly. They are also reversible with systemic steroids.

In AIED, the immune system attacks explicitly the inner ear. Although rare, it does affect every 15 in 100,000 persons. Unfortunately, it is not widely known, diagnosed, studied, or tested.

AIED is an excellent example of fluctuating bilateral hearing loss. It progresses from weeks into months. What is even more challenging is that there are no diagnostic tests to confirm it, and it is a diagnosis of exclusion.

Like many autoimmune conditions, it is treated with a trial of steroids.

Cardiovascular Conditions

Sudden sensorineural hearing loss can take place with cardiovascular conditions where the blood supply is occluded. This could be seen in stroke, hypertension, peripheral artery disease, and coagulopathy.

Often this involves a cut-off of the blood supply to the brainstem area, though not always necessary. Even an infarction or hemorrhage of the anterior inferior cerebellar artery (AICA) affects the auditory and vestibular function. People can have cochlear hearing loss or retro cochlear hearing loss.

As you have seen, there are a whole host of conditions that cause hearing loss. For those with hearing loss, your doctor should be able to pinpoint the cause of your impairment right away. In some cases, they may need an extensive set of tests to do so.

Listen & Move

No matter the cause of your hearing loss, you should still seek professional help. Hearing loss is preventable and treatable.

If you are experiencing hearing loss, you must first learn why to know how to treat it. An ENT can help you diagnose, treat your hearing loss, and prevent it from worsening, and all you must do is listen and act on it.

Sources:

1.    https://www.who.int/health-topics/hearing-loss

2.     Lin J, Huang H, Lv G, et al. Chronic prenatal hypoxia impairs cochlear development, a mechanism involving connexin26 expression and promoter methylation. Int J Mol Med. 2018;41(2):852-858. doi:10.3892/ijmm.2017.3303

3.     Richardson MP, Reid A, Tarlow MJ, et alHearing loss during bacterial meningitisArchives of Disease in Childhood 1997;76:134-138.

4.     Cohen BE, Durstenfeld A, Roehm PC. Viral causes of hearing loss: a review for hearing health professionals. Trends Hear. 2014;18:2331216514541361. Published 2014 Jul 29. doi:10.1177/2331216514541361