How and Why Hearing Loss Occurs
Hearing loss is classified by the type of damage caused to the auditory system. The three basic types of hearing loss are conductive hearing loss, sensorineural hearing loss, and mixed hearing loss.
When sound is not conducted efficiently through the outer ear canal to the eardrum and tiny bones (ossicles) of the middle ear, conductive hearing loss occurs. This type of hearing loss usually involves a reduction in sound level or the ability to hear faint sounds, and can usually be corrected medically or surgically. Possible causes of conductive hearing loss can include, but are not limited to:
- Fluid in the middle ear from colds
- Ear infections
- Perforated eardrum
- Benign tumors
- Swimmer’s ear
Damage to the inner ear, or to the nerve pathways from the inner ear to the brain, are what cause sensorineural hearing loss. Typically, this type of hearing loss cannot be medically or surgically corrected, and is the most common type of permanent hearing loss. Sensorineural hearing loss reduces one’s ability to hear faint sounds – even when the speech is loud enough to hear, it may still sound muffled. Possible causes include:
- Drugs that are toxic to hearing
- Head trauma
- Exposure to loud noise
- Malformation of the inner ear
Mixed hearing loss occurs when conductive and sensorineural hearing loss occur in combination with each other. In these cases, there may be damage in the outer or middle ear and in the inner ear or auditory nerve, thereby causing this “mixed” loss of hearing.
Hearing loss is a significant public health issue; it is the third most common physical condition after arthritis and heart disease, and can affect people of all ages. Hearing loss affects:
- About 17 percent of adults in the U.S., or roughly 36 million people.
- One in three people over the age of 65.
- 60 percent of people in the work force or educational settings.
- Roughly 2-3 out of every 1,000 children, who are either hard of hearing or deaf.
- Nearly 30 per 1,000 school children, who suffer with some form of hearing loss.
Statistics sources: National Information Center on Deafness and Other Communication Disorders, National Institutes of Health, National Council on Aging, and the MarkeTrak VIII Study by Sergei Kochkin, Ph.D.