Causes, Types & Degrees of Hearing Loss

Woman with hearing loss or hard of hearing

Composing over 5% of the world’s population, people with difficulty hearing experience various types of hearing loss, with unique and often overlapping causes. Some causes of hearing loss emerge at early ages, while others typically affect aging populations. Other causes can occur anytime across a lifespan, with some originating in prenatal or perinatal periods.

Common Causes of Hearing Loss Over a Lifespan

Multiple, interconnected factors can contribute to hearing loss throughout a person’s life. Without accounting for each person’s unique circumstances and the potential for concurrent causes, some of the most common causes of hearing loss include:

Disease

Infections and diseases are leading causes of many types of hearing loss. These can be specific to certain age periods or can occur any time in life:

  • Ear infections
  • Sinus infections
  • Bacterial infections
  • Viral infections
  • Tumors
  • Allergies
  • Stroke
  • Medicines
  • Otosclerosis

Genetics & Age

Ear examination

Some hearing loss results from genes and inherited traits, while others relate to specific age periods or are exacerbated by aging:

  • Hereditary hearing loss
  • Progressive genetic hearing loss
  • Low birth weight
  • Age-related afflictions
  • Nutritional deficiencies

Physical Damage/Blockage

Conductive hearing loss types generally stem from physical damage to sensitive parts of the ear, including middle and inner ear structures:

  • Ruptured eardrum
  • Impacted earwax
  • Head or ear trauma
  • TMJ disorders
  • Smoking
  • Sudden loud noise
  • Fluid buildup/excessive swelling

Consistent Exposure to Loud Noise

closeup of earbuds and cord
These causes accrue over time and prolonged exposure to high decibels rather than a singular, sudden noise event causing damage:

  • High-volume headphone or earbud usage
  • Loud concerts
  • Noisy workplaces
  • Firing ranges
  • Etc.

Clinical degrees of Hearing Loss

The American Speech-Language-Hearing Association categorizes hearing loss degrees as follows:

  1. Mild: soft sounds become difficult to hear, typically below the 30dB threshold
  2. Moderate: sounds like moderate rainfall or low talking become difficult to hear, as well as anything falling below the 50dB range
  3. Severe: difficulty hearing group conversations or an alarm clock may indicate severe hearing loss, with things below 79dB being difficult to hear
  4. Profound: all but the loudest noises are inaudible, if anything at all. Any sound below 90dB is largely inaudible

Types of Hearing Loss

female ear

The Mayo Clinic has identified three main types of hearing loss, differentiated by what part of the hearing system is affected. These include:

  • Sensorineural hearing loss
  • Conductive hearing loss
  • Mixed hearing loss

Here we explore those three plus a few additional types of hearing loss.

Sensorineural hearing loss (SNHL)

The most common type of hearing loss occurs as a result of damage to the inner ear nerves and hair cells. The damage can be caused by noise, disease, age, physical trauma or related factors. According to the National Institutes of Health (NIH) it affects 5 to 27 people per 100k, adding around 66k new cases each year. Unlike other types of hearing loss, sensorineural hearing loss is rarely corrected by surgery or medicine; instead, hearing aids are the most common course of corrective action.

Causes for sensorineural hearing loss include:

  • Congenital: hearing loss that exists at birth, often caused by in-utero infections or genetic syndromes.
  • Presbycusis: 1 in 3 people over age 65 will experience this age-related hearing loss, which comes on gradually.
  • Noise-induced: originates from acute or chronic exposure to elevated decibel levels, which damages various structures in the inner ear.
  • Injury induced: the result of a trauma to the head (particularly ear, nose, & throat) which damages internal ear structures.
  • Meniere’s disease: in addition to hearing loss from damage to inner ear structures, this disorder can also cause vertigo and tinnitus.
  • Ototoxicity: hearing loss resulting from certain medications or exposure to types of environmental pollutants like cadmium and lead.
  • Vestibular Schwannoma: also known as acoustic neuroma, it leads to hearing loss via noncancerous tumor growth on the cochlear nerve which disrupts signals to the brain.

Conductive hearing loss (CHL)

Conductive hearing loss caused by obstructions of structures within the middle or outer ear. Whether the obstruction is a foreign body, excess of earwax, swelling, bone or other structural abnormalities, hearing loss occurs due to the inability of soundwaves to effectively reach the inner ear, where sounds are processed. A ruptured eardrum may also be a cause for conductive hearing loss.

A person with conductive hearing loss may experience muffled sounds or the inability to hear softer sounds. Rehabilitation by qualified audiologists and medical interventions like surgery or medicines can be effective in correcting this type of hearing loss.

Causes for conductive hearing loss include:

  • Eardrum damage
  • Loud Noise
  • Earwax buildup and impaction
  • Otosclerosis (abnormal bone growth)
  • Ear tumors
  • Ear canal or middle ear infection

Mixed hearing loss (MHL)

Mixed hearing loss is a combination of conductive and sensorineural hearing loss, occurring when an issue causing conductive hearing loss happens in someone with a degree of sensorineural hearing loss.

Any issue that can cause either CHL or SNHL can cause MHL. For example, an elderly man with presbycusis may also have an excess of earwax which worsens the degree of hearing loss from both. In a case like this, the excess earwax can be removed, which will help alleviate the conductive hearing loss, but the sensorineural hearing loss remains. In this case an additional hearing aid can be an effective treatment once impacted earwax is removed.

Other Types of Hearing Loss

Aside from the main three types of hearing loss, some people experience these other varieties:

Unilateral hearing loss (UHL)

UHL, sometimes referred to as single-sided deafness, is the condition of having normal hearing in one ear and mild to profound hearing loss in the other. This can occur at birth or throughout a lifespan as a result of disease, physical damage, and more. Typical causes of single-ear hearing loss range from physical trauma, exposure to loud noise and infection to genetics and ear abnormalities.

Sudden hearing loss (SSHL)

Sudden hearing loss, otherwise known as sudden sensorineural hearing loss (SSHL), can happen instantly or can unfold over the course of a few days. It usually occurs within the inner ear, frequently only affects one ear and can be accompanied by a loud “pop” sound or a feeling of ear fullness or tinnitus. Only about 10% of those experiencing SSHL are diagnosed with an official cause, which can make diagnosis difficult. The most common causes of sudden hearing loss are infections, head trauma, loud noise exposure, ototoxicity, and a range of autoimmune diseases.

When to Get Medical Help for Hearing Loss

Anytime hearing loss causes trouble, whether it’s a sudden loss of hearing or a slow degradation, seek the advice of an audiologist. If you’re finding it more difficult to hear conversations in noisy environments, notice that speech sounds are muffled, have trouble hearing things you normally wouldn’t or if you have prolonged ringing in your ears (tinnitus), consult with a doctor or audiologist.

Contact your nearest audiologist or get assistance online to determine the extent, cause and type of hearing loss, and start on a path to hearing more clearly today.

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