Causes of conductive hearing loss include
- fluid in the middle ear (e.g., from upper respiratory infections, otitis media, or serous otitis media);
- poor eustachian tube function;
- perforated tympanic membrane;
- benign tumors;
- head trauma-physical head injury can lead to skull fractures, a hole in the tympanic membrane, and damage to middle ear structures;
- impacted cerumen;
- infection in the ear canal (external otitis);
- swimmer's ear (otitis externa);
- presence of a foreign body;
- absence or malformation of the outer ear, ear canal, or middle ear.
Mixed hearing loss is caused by a combination of one or more causes of conductive hearing loss and one or more causes of sensorineural hearing loss.
Causes of sensorineural hearing loss include:
- Noise - the type as well as the level of noise and the length of time spent listening to the noise can create risk for noise-induced hearing loss. See the U.S. Department of Labor Occupational Safety and Health Administration (OSHA) standards for occupational noise exposure, the National Institute for Occupational Safety and Health (NIOSH) criteria [PDF], and the World Health Organization - International Telecommunication Union standard [PDF] for recommendations.
- Genetics-disorders can be autosomal recessive or autosomal dominant. Other, rarer, types of genetic hearing loss include X-linked (related to the sex chromosome) or mitochondrial inheritance patterns. Genetic disorders that include hearing loss include neurofibromatosis 2 and Waardenburg Syndrome (Smith, Shearer, Hildebrand, & VanCamp, 2014).
- Ototoxicity-drugs known to be ototoxic include
- drugs used in chemotherapy regimens (cisplatin, carboplatin, and nitrogen mustard),
- aminoglycoside antibiotics (streptomycin, neomycin, and kanamycin),
- salicylates in large quantities (aspirin),
- loop diuretics (lasix and ethacrynic acid).
- Head trauma-physical head injury can lead to traumatic brain injury (TBI), skull fractures, and damage to the inner ear.
- Autoimmune inner ear disease (AIED)-AIED occurs when the body's immune system attacks cells in the inner ear that are mistaken for a virus or bacteria and can happen in isolation (as just labyrinthine disease) or as part of other systemic autoimmune disorders. Systemic immune diseases known to have caused AIED include
- Cogan syndrome,
- relapsing polychondritis,
- Wegener's granulomatosis,
- polyarteritis nodosa,
- Sjogren syndrome,
- lyme disease.
- Bacterial, viral, or parasitic infections, including
- Acoustic neuroma
- Large vestibular aqueduct
- Meniere's disease
- Vascular deficits, including
- vascular disease associated with mitochondriopathy,
- vertebrobasilar insufficiency (high blood pressure and diabetes),
- red blood cell deformability,
- sickle cell disease,
- cardiopulmonary bypass.
Approximately one-third of Americans between ages 65 and 74 and nearly half over the age of 75 have hearing loss (NIDCD, 2010). Many older adults will have both hearing impairment and cognitive loss, and together these losses will affect communication, social participation, and quality of life (Pichora-Fuller, Dupuis, Reed, & Lemke, 2013).
Lin et al. (2013) found that individuals with baseline hearing loss had greater rates of cognitive decline over time than did individuals with normal hearing. Further investigation is needed to clarify this relationship and to determine whether hearing loss is a risk factor for dementia or a sign of early-stage dementia. One hypothesis is that when a hearing loss is present, greater cognitive resources are dedicated to auditory processing, leaving fewer resources for other cognitive processes, like working memory (Peelle, Troiani, Grossman, & Wingfield, 2011). Recent research suggests the possibility of a shared etiological pathway responsible for both hearing loss and dementia (Gallacher et al., 2012).
It is important for clinicians to differentiate between hearing loss and cognitive impairment and to identify when one or both of these conditions are present. See dementia.