Hearing loss is a common problem. About 15 percent of U.S. adults say they have trouble hearing, reports the Centers for Disease Control and Prevention. Hearing loss is especially prevalent in older adults, with nearly 36 percent of people over 65 reporting difficulty hearing. The many causes of hearing loss fall into 2 general categories. Conductive hearing loss refers to disruption of sound waves traveling through the outer or middle ear. With sensorineural hearing loss, disease or injury disrupts normal function of the inner ear or nerve pathways that transmit sound signals to the brain.
Sound waves transmitted through the ear canal vibrate the eardrum, which transmits those vibrations through small bones in the middle ear to the inner ear. Anything that dampens the sound waves or vibrations results in hearing loss. An accumulation of ear wax in the ear canal, infections and buildup of fluid in the middle ear are common causes of conductive hearing loss. Blockage of the eustachian tube -- which allows air into the middle ear -- can also blunt sound wave transmission. In addition, the small bones of the middle ear sometimes become less mobile due to buildup of bone around them or scarring due to ear infections.
Noise and Advanced Age
Two of the most common causes of hearing loss develop gradually. Exposure to loud noise over many years -- such as listening to loud music or working in a noisy environment -- can damage the inner ear and cause sensorineural hearing loss. Aging also contributes to hearing loss, typically beginning with difficulty hearing high-pitched sounds. As you age, hearing-associated nerve cells and cells within the inner ear are slowly lost. This age-related sensorineural hearing loss is called presbycusis.
Infection and Medication
Several diseases and medications can contribute to hearing loss. Ménière disease is a condition that causes increased fluid in the inner ear, and this can sometimes damage the hearing cells. Sensorineural hearing loss also sometimes occurs with infectious diseases such as meningitis, syphilis, measles, mumps and cytomegalovirus. In addition, this type of hearing loss sometimes occurs as a side effect of medication. Certain types of antibiotics, water pills, chemotherapy and antimalarial drugs can damage the inner ear and cause sensorineural hearing loss.
Ear, Head and Brain Injuries
Hearing loss can occur with certain types ear or head injuries. The eardrum can be ruptured with a cotton swab, causing a temporary conductive hearing loss. Skull fractures and exposure to extremely loud sound -- such as an explosion or amplified concert music -- can cause also damage the ear and lead to sudden deafness. Interruption of blood flow to the inner ear or parts of the brain involved in hearing may also lead to hearing loss. Stroke and bleeding in the brain due to a head injury are frequent causes.
Tumors that damage the ear, hearing nerves or other parts of the brain involved in hearing can cause deafness in one ear. Examples include acoustic neuroma, a tumor of the hearing and balance nerve, and cholesteatoma, a tumor of the middle ear. Certain medical conditions can also contribute to hearing loss. These include kidney failure, an underactive thyroid, multiple sclerosis, diabetes, inflammation of the blood vessels and some genetic diseases.
When to See Your Doctor
Many types of hearing loss develop gradually, so you may not recognize the symptoms. If it seems people around are mumbling or you like the television louder than other people in your household, talk with your doctor as you may have hearing loss. See your doctor right away if you experience sudden hearing loss, especially if you've had a recent head injury, or your hearing difficulty is accompanied by other symptoms such as a drooping face, numbness or paralysis, dizziness, slurred speech or vision problems.
- Centers for Disease Control and Prevention: Summary Health Statistics for U.S. Adults: National Health Interview Survey, 2012
- Merck Manual Professional Version: Introduction to Inner Ear Disorders
- Merck Manual Professional Version: Introduction to Middle Ear and Tympanic Membrane Disorders
- Merck Manual Professional Version: Dermatitis of the Ear Canal (Chronic Otitis Externa)
- American Family Physician: Differential Diagnosis and Treatment of Hearing Loss
- Glasscock-Shambaugh Surgery of the Ear, Sixth Edition; A. Julianna Gulya, et al.