What causes hearing loss if not due to an autoimmune disorder?

Causes of Hearing Loss Beyond Autoimmune Disorders

Hearing loss has multiple etiologies beyond autoimmune disorders, with age-related changes, genetic factors, and environmental exposures being the most common causes. 1

Age-Related Hearing Loss (Presbycusis)

Age-related hearing loss (ARHL) is the most common cause of hearing loss in adults, affecting:

• 65.3% of adults over 71 years
• 60% of individuals by age 70
• 80% of individuals over 85 years 1

ARHL results from mixed pathology involving:

• Degenerative changes to cochlear and neural structures
• Genetic predisposition (approximately 50% heritable)
• Mitochondrial dysfunction and mutations
• Reactive oxygen species and apoptosis 1

Genetic Causes

Genetic factors account for approximately 50% of congenital hearing loss cases: 1

• 70% are nonsyndromic (hearing loss only)
• 30% are syndromic (associated with other clinical findings)
• Inheritance patterns include:
  • 77% autosomal recessive
  • 22% autosomal dominant
  • 1% X-linked
  • Variable proportion due to mitochondrial inheritance (1-20% depending on population) 1

At least 77 loci for nonsyndromic hearing impairment have been identified, with 50+ auditory genes sequenced 1

Environmental and Medical Causes

Ototoxic Medications

• Aminoglycosides cause permanent bilateral auditory ototoxicity, especially with:
  • Pre-existing renal damage
  • Higher doses or extended treatment periods
  • High peak or trough serum concentrations 2
• Other ototoxic drugs include:
  • Loop diuretics (furosemide)
  • Cisplatin
  • Chemotherapy agents 2, 1

Infections

• Bacterial meningitis
• Viral infections (CMV, herpes, rubella)
• Syphilis (Treponema pallidum)
• Lyme disease (Borrelia burgdorferi)
• HIV and associated opportunistic infections 1, 3

Vascular and Inflammatory Mechanisms

• Inflammation-induced vasospasm leading to cochlear ischemia
• Proinflammatory cytokines (IL-1, endothelin-1, TNF) causing vasoconstriction
• Vascular inflammation from systemic diseases 4

Chronic Medical Conditions

• Diabetes (2x higher prevalence of hearing loss)
• Hypertension
• Hypercholesterolemia 1

Trauma and Noise Exposure

• Acoustic trauma
• Head trauma (especially basal skull/temporal bone fractures)
• Occupational noise exposure 1

Sudden Sensorineural Hearing Loss

Sudden sensorineural hearing loss (SSNHL) is often idiopathic (85-90% of cases) but may be caused by:

• Vascular mechanisms
• Viral infections
• Metabolic disorders (MELAS syndrome)
• Vestibular schwannoma (rare)
• Ménière's disease 5

Risk Factors for Progressive Hearing Loss

• Advanced age (risk doubles with each decade of life)
• Male gender (progression twice as fast as in women)
• Smoking and passive smoke exposure
• Diabetes
• History of exposure to loud noises
• Genetic predisposition 1

Clinical Implications

Hearing loss has significant impacts beyond auditory function:

• 69% of hearing-impaired older adults report depression vs. 31% of non-hearing-impaired
• Adults with hearing loss are twice as likely to be unemployed or partly unemployed
• Hearing loss is associated with social isolation and decreased physical activity 1

Diagnostic Approach

For non-autoimmune hearing loss, evaluation should focus on:

1. Detailed history of exposure to ototoxic medications
2. Assessment for genetic factors and family history
3. Evaluation of chronic medical conditions (diabetes, hypertension)
4. Audiometric testing to characterize the pattern and severity of hearing loss
5. Imaging (MRI preferred) when indicated for asymmetric or sudden hearing loss 1, 5

Early identification and management of modifiable risk factors is essential to prevent progression and improve quality of life in patients with hearing loss.