Hearing loss is a decrease in the ability to hear. It can vary from mild to total loss of hearing and occur in one or both ears. There are three parts of the ear. Problems that contribute to hearing loss can occur in one or more of these parts.

About 28 million Americans (one in every ten) have hearing loss. It is one of the most common health conditions in the United States. Although it affects people of all ages, the numbers increase significantly with age.

Recent statistics estimate that 3-4 babies in 1,000 are born with partial or complete hearing loss (making this condition the most common birth defect). Seventeen in 1,000 children under age 18 have some hearing loss. Fourteen percent of people ages 45-64 have hearing loss. One-third of people over the age of 60 have hearing loss, and 40%-50% of people age 75 and older having hearing loss.

Approximately half of the cases of hearing loss in children result from genetic factors. Problems during birth or soon after can also lead to hearing loss, such as lack of oxygen, severe ]]>jaundice]]> , or bleeding in the brain.

Two of the most common causes of hearing loss in older adults are ]]>presbycusis]]> .

Presbycusis develops slowly as a person ages, especially after age 50, and continues to worsen. It is caused by a combination of hereditary and environmental factors, including exposure to noise and smoking. This condition makes it hard for a person to hear normal conversation and tolerate loud sounds. It sometimes involves permanent damage in the inner ear.

]]>Tinnitus]]> is ringing, hissing, or roaring sounds in the ears. It can occur with any kind of hearing loss and often is caused by loud noise or certain medications. The condition can also be a sign of other health problems, such as allergies and heart and blood vessel conditions. Tinnitus can occur on and off and can stop completely.

Anatomy of the Ear

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There are three main types of hearing loss: conductive , sensorineural , and mixed .

Conductive hearing loss is due to problems in the outer or middle ear that interfere with sound passing to the inner ear. It usually involves a decrease in sound level (ability to hear faint sounds) and can often be corrected by medical or surgical treatment.

Causes of conductive hearing loss:

• Blockage by ear wax
• Fluid in the middle ear
• Ear infection ( ]]>otitis media]]> )
• ]]>Otosclerosis]]> (a disorder of the bones in the middle ear)
• Hole in the eardrum
• Abnormalities in the outer ear, middle ear, or ear canal
• Tumors
• Trauma leading to disruption of the middle ear ossicles

Sensorineural hearing loss is due to damage to the inner ear (cochlea) or the major nerve pathway (8th cranial nerve) that goes from the inner ear to the brain. In addition to a decrease in sound level, it also affects the ability to understand speech. This type of hearing loss is permanent—it cannot be corrected medically or surgically but can be treated with hearing aids and assistive devices.

Causes of sensorineural hearing loss include:

• Excess noise
• Birth injury
• Hereditary factors
• Aging
• Exposure to toxic substances, including drugs like:
  • Streptomycin
  • Gentamicin
  • Chemotherapy drugs
  • Diuretics
  • Steroids
  • Heart medicines
  • Quinine
  • Anesthetics
  • Aspirin-containing drugs
• Tumors
• Cardiovascular disease
• ]]>Multiple sclerosis]]>
• Viruses ( ]]>measles]]> , ]]>mumps]]> , adenovirus, ]]>rubella]]> )
• History of ]]>meningitis]]> or ]]>syphilis]]>
• External trauma to the ear

Mixed hearing loss is due to a combination of both conductive and sensorineural hearing loss.

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