Hearing Loss

Descriptive text is not available for this image BASICS

Hearing loss (HL) is one of the most common conditions that interfere with a person’s ability to work and lead a normal life; when occurring at birth, can limit child development and speech; when onset occurs in childhood, can lead to poor literacy; when occurs later in life, can contribute to the development of dementia

DESCRIPTION

  • HL is the inability to perceive sound. Divided by different levels of severity:
    • Mild (>25 dB): difficult to understand speech in a loud environment.
    • Moderate (>40 dB): affects speech development in children
    • Severe (>60 dB): able to hear only loud sounds; no speech
    • Profound (>80 dB): unable to hear any sound
  • Also distinguished as conductive or sensory neural:
    • Conductive hearing loss (CHL): external and middle ear
    • Sensorineural hearing loss (SNHL): inner ear (cochlea) and/or acoustic nerve/acoustic central nuclei

EPIDEMIOLOGY

>1.5 billion people live with HL, 403 million (26%) of whom have moderate-to-complete HL in their better ear.

Prevalence

Hearing impairment is the third cause of disability worldwide. WHO estimates that 60% of HL in children is due to preventable causes. In the United States, the prevalence doubles with every 10-year increase in age.

ETIOLOGY AND PATHOPHYSIOLOGY

  • Causes in children:
    • Infections
      • Middle ear infections (otitis media [OM])
      • Mumps, rubella measles, meningitis (cochlea)
    • Birth related causes (ototoxic meds, low birth, prematurity)
    • Genetic
      • >100 mutations: congenital HL in newborns
      • Syndromes (e.g., Stickler syndrome, Alport syndrome)
    • Other causes
      • Impacted cerumen
      • Perforation of tympanic membrane (TM), Cholesteatoma (chronic OM)
  • Causes in adults:
    • CHL
      • Impacted cerumen
      • External ear infection (swimmer’s ear)
      • Cholesteatoma and chronic OM
      • Barotrauma
      • Radiotherapy (damage to middle ear and TM)
      • Otosclerosis
    • SNHL
      • Acoustic neuroma compression of 8th nerve.
      • Cholesteatoma invading the inner ear/cochlea
      • Ménière disease with cochlear hydrops
      • Chronic diseases
    • Diabetes, HTN: microvascular/macrovascular changes in inner ear and auditory system
    • Autoimmune diseases: hypothesized that autoantibodies destroy hair cells of the inner ear and vestibular nerve; common in lupus, Cogan disease, vitiligo, sarcoidosis, rheumatoid arthritis
    • Ototoxic drugs: damage to hair cells
      • Aminoglycosides
      • Cisplatin
      • Radiotherapy: damages inner ear, auditory, and vestibular nerve pathways
      • Macrolides: caution in individuals with personal/family history of HL
    • Substance use disorder: permanent HL (opioids) or temporary (cocaine, heroin)
  • Environmental exposure
    • Noise: permanent damage to hair cells
    • Tobacco exposure
  • COVID-19 infection: caused by the inflammation or autoimmune process
  • Age-related HL
    • Gradual and progressing degeneration of inner ear but also of the central auditory nerve pathways; worsening with age; starts with high frequencies; worsening speech intelligibility
      • Sudden HL is often associated with tinnitus and vertigo.
        • Possible causes: viral, vascular (brainstem stroke), illicit drugs, COVID-19, autoimmune

RISK FACTORS

  • Lifestyle
    • Smoking 2.8% incidence
    • Chronic conditions 3.8% incidence (metabolic syndrome, diabetes, HTN)
  • Leisure
    • Loud prolonged noise exposure (hunting, playing music through headphones, attending concerts)
    • Illicit drug use
  • Genetic susceptibility
  • Infections

GENERAL PREVENTION

Based on reduction of risk factors

  • Noise induced HL is 16% of the disabling HL in adults worldwide accounting for 4 million daily is attributable to occupational noise exposure.
    • Hearing conservation program: required for work exposure >85 dB; includes noise exposure monitoring; personal hearing protection; audiometric evaluations; employee education
    • Antioxidant drugs may help the regeneration of hair cells of organ of Corti (unclear mechanism).
    • Hearing protection during leisure activity noise exposure (appropriate headphones while attending concerts, play music, hunting)
  • Nutrition
    • Balanced and adequate nutrition during pregnancy and childhood, reduces HL in adult life and overall life span.
    • Supplements
  • Antioxidants, carotenoids, folate, maintenance of antioxidants homeostasis
  • Vitamin A and zinc: decrease frequency of OM episodes

COMMONLY ASSOCIATED CONDITIONS

Tinnitus and vertigo are common in SNHL.

There's more to see -- the rest of this topic is available only to subscribers.