Hearing loss is a decrease in the ability to perceive sounds. In adults, hearing loss can be partial or total, sudden or gradual, temporary or permanent. It can affect one ear or both. Currently in the United States, 28 million people over age 3 have some form of hearing loss. The condition affects approximately 3% of all adult men and women. In general, the risk of hearing loss increases with age. Between 24% and 40% of adults over age 65 have difficulty hearing. Thirty percent of people over age 85 are deaf in at least one ear.
To understand hearing loss and treatment, it helps to know how hearing works. Sound enters the ear and strikes the eardrum (tympanic membrane). This causes the eardrum to vibrate. The eardrum's vibrations are amplified through the middle ear by three tiny bones. Inside the ear, the vibrations are transformed into nerve impulses. These nerve impulses travel to the brain, where they are interpreted as sounds.
Because the outer ear and middle ear transmit (or conduct) sound, any injury to this part of the hearing pathway is called conductive hearing loss. Sensorineural hearing loss is injury to the inner ear, eighth cranial nerve and brain, which all deal with the production, transmission and interpretation of nerve impulses.
In adults, some of the most important causes of hearing loss are:
Middle ear disease — A bacterial infection of the middle ear can injure the eardrum, disrupt the middle-ear bones, or cause fluid buildup.
Noise — Without adequate ear protection (earmuffs or earplugs), loud sounds can injure delicate cells within the ear. This is a form of sensorineural hearing loss, and it is the most common cause of hearing loss among American adults. Noise-induced hearing loss can happen because of a single brief burst of an extremely loud sound, such as a gunshot or firecracker. It is more often the result of long-term exposure to loud sounds of slightly lower intensity, such as factory noise or rock music. Among U.S. workers, noise-induced hearing loss is the most common of all occupational injuries. It is a significant health problem among carpenters, miners, plumbers, factory workers, farmers, construction workers and workers exposed to aircraft, sirens or explosives. People can also develop noise-induced hearing loss from recreational activities, such as listening to very loud music, operating a personal watercraft (such as Jet Ski and WaveRunner) or snowmobile, shooting firecrackers or guns, or operating a loud lawnmower or leaf blower.
Otosclerosis — This conductive hearing loss involves the abnormal overgrowth of one or more bones in the middle ear. It prevents the small bones from moving normally. Otosclerosis often runs in families. It strikes 1% of American adults, and is especially common among white, middle-aged women.
Acoustic neuroma — This noncancerous (benign) tumor grows on part of the eighth cranial nerve, which carries signals to the brain. Because this tumor develops near parts of the body that help control balance as well as hearing, it often causes dizziness and equilibrium problems in addition to gradual hearing loss. Acoustic neuromas most often occur in adults between the ages of 30 and 60.
Meniere's disease — This typically causes dizziness, hearing loss, ringing in the ears (tinnitus) and a sensation of fullness or stuffiness in one or both ears. Although research suggests that Ménière's disease is related to a change in the volume of a fluid inside the ear, the reason for this volume change remains unknown. Ménière's disease currently affects three to five million Americans.
Trauma — Many types of accidents can cause hearing loss, including stab wounds, gunshots or being hit on the ear or skull. Hearing loss can come from a blast injury to the eardrum from the force of an explosion or simply from a cotton swab (Q-tip) that ruptures the eardrum during an attempt to clean the ear canal.
Sudden sensorineural hearing loss — This is a medical emergency. A person loses hearing over a period of three days or less. In 85% to 90% of cases, the cause is unknown, although many doctors believe that the underlying problem may be a viral infection. Doctors diagnose about 4,000 Americans with this type of hearing loss each year. In 90% of the cases, only one ear is affected.
Drugs — Many prescription and nonprescription medications can damage the ear and cause hearing loss. These include:
Antibiotics, such as erythromycin (several brand names), vancomycin (Vancocin), tetracycline (several brand names) and aminoglycosides, such as gentamicin (several brand names), streptomycin (Zanosar), tobramycin (Nebcin) and amikacin (Amikin)
Anticancer chemotherapeutic drugs, such as cisplatin (Platinol), 5-fluorouracil (Ancobon) and bleomycin (Blenoxane)
Aspirin
Antimalaria drugs
Age — Age-related hearing loss, also known as presbycusis, is not a single disease, but a category for the cumulative effects of aging on the ears. In most cases, hearing loss begins after age 60, and is usually more noticeable in men than women. Both ears are affected. It is typically harder to hear high-pitched tones (women's voices, violins) than low-pitched ones (men's voices, bass guitar). Because this usually occurs gradually over a period of years, the person may not realize that he or she has difficulty hearing. A family member may bring the problem to the person's attention.
Other causes — There are more than 100 different causes of hearing loss in adults. The most common reversible cause is severe buildup of earwax in the ear canal and acute infections of the external ear or middle ear.
From Health A-Z, Harvard Health Publications. Copyright 2007 by the President and Fellows of Harvard College. All rights reserved. Written permission is required to reproduce, in any manner, in whole or in part, the material contained herein. To make a reprint request, contact Harvard Health Publications. Used with permission of StayWell.
On World Vegetarian Day, most people aren't willing to trade in their turkey for tofurkey. Luckily, you can still reap the benefits of vegetarianism by trying flexitarianism on for size.
Meatless Meals Benefit Your Health
