Age-Related Hearing Loss : Causes and Symptoms, Treatment

by Food and Drug Administration (FDA)

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Causes and Symptoms

People lose their hearing when they age because of gradual changes in their entire auditory system. Sometimes the loss occurs due to complex changes along the nerve pathways to the brain. According to NIDCD, presbycusis is usually caused by disorders of the inner ear or auditory nerve (sensorineural disorders). Sensorineural hearing loss also can occur as a result of hereditary factors, various health conditions, and the side effects of some medicines, such as aspirin and certain antibiotics. Repeated exposure to noise and loud music is another cause of sensorineural hearing loss.

Presbycusis also may be caused by changes in the blood supply to the ear because of heart disease, high blood pressure, blood vessel conditions caused by diabetes, or other circulatory problems. The loss may be mild, moderate, or severe.

Sometimes hearing loss is a conductive hearing disorder, meaning the loss of sound sensitivity is caused by abnormalities of the outer ear, middle ear, or both. Such abnormalities may include reduced function of either the eardrum or the three tiny bones that carry sound waves from the eardrum to the inner ear.

Sounds often seem less clear and lower in volume for a person with presbycusis. The most common symptoms include sounds of mumbled or slurred speech by others; difficulty in distinguishing high-pitched sounds; difficulty in understanding conversations, particularly when there is background noise; hearing men's voices more easily than women's; and increased sensitivity to loud noises. Tinnitus, a ringing, roaring, hissing, or other sound, may occur in one or both ears.

Age-related hearing loss first affects the ability to hear the highest pitches and only later affects lower pitches. Loss of the ability to hear high-pitched sounds such as "s" and "th" often makes it more difficult to tell them apart. Understanding the consonant sounds in speech is dependent upon our ability to hear high pitches, says James K. Kane, Ph.D., an audiologist and scientific reviewer in the FDA's Office of Device Evaluation. "If one cannot hear the high-pitched sounds, speech becomes less intelligible."

But most important, the symptoms of presbycusis may resemble other conditions or medical problems, so it's important to consult a physician for a diagnosis. Even though McKinney's first visit to the otolaryngologist failed to reveal anything more than minor age-related hearing loss, she says, "I still couldn't hear." Nearly a year later, and without a medical evaluation, McKinney mail-ordered three different types of hearing aids in an attempt to find something that would help her hear better.

But none fit. "There wasn't one that was comfortable," McKinney says. She returned all of them for a refund.

Treatment

Since there is no way to reverse age-related hearing loss, treatment is focused on functional improvement — compensating for the loss as much as possible. Hearing aids are the mainstay of treatment, but these devices don't restore hearing to normal. People can, however, reasonably expect a hearing aid to improve their ability to communicate.

McKinney says the manufacturer of one of the hearing aids she tried advised her to consult a second hearing specialist — an audiologist, who discovered that both of her ear canals had collapsed.

"Collapsed ear canals are not that uncommon," says Kane. "But the first step in buying a hearing aid is making sure your problem is diagnosed properly, since hearing loss may be a symptom of a more serious medical condition." Kane explains that health care providers overcome the problem of a collapsed ear canal when taking an impression for a hearing aid by gently pulling up and back on the outer ear to straighten the canal before injecting the impression material. This, he says, is done "to correctly represent the anatomy of the person's ear, in order to get a proper fit."

Other hearing devices, such as built-in telephone amplifiers and FM systems that make sounds clearer — with or without a hearing aid — by delivering sound waves like a radio, also can help people with age-related hearing loss communicate. Personal listening systems help people hear what they want to hear while eliminating or lowering other noises around them. Some, called auditory training systems and loop systems, make it easier for people to hear someone in a crowded room or group setting.

Lip reading, which relies on visual cues to determine what's being said, is another option, usually used by people who have profound hearing loss and receive very limited benefit from hearing aids. People who use this method to help overcome hearing loss pay close attention to people's mouths when they talk. Special trainers can help people learn these functions. Even so, Kane says, only about 25 percent of the speech sounds we produce are visible on our lips.

In contrast, Kane says that speech reading encompasses much more than just watching lip movements. It makes use of the entire communication environment, such as awareness of talker location, time of day, person speaking, knowledge of conversation topic, and body language. Kane adds, "All of these provide cues as to what words are probable and aid in understanding what is said." Both lip reading and speech reading, he says, are beneficial adjuncts to hearing aid use.

Currently, there is significant research being done on restoration of sensory hair cells. A study done by researchers from the Howard Hughes Medical Institute in Chevy Chase, Md., and reported in the Feb. 18, 2005 issue of Science, indicates that deleting a specific gene permits the proliferation of new hair cells in the cochlea. The study's authors suggested that there might be a gene that produces a protein that acts as a permanent "brake" on hair-cell regeneration.

Functional hair cells have also been shown to regenerate in the inner ear after delivery of a gene that controls hair cell development using gene therapy, as reported in the March 2005 issue of Nature Medicine. These experiments, Staecker says, may help develop specific drugs to repair the damaged inner ear and restore some types of hearing loss.

About the Author

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FDA is A United States government body that oversees medical devices, including contact lenses, intraocular lenses, excimer lasers and eyedrops. In the US, these products must be approved by the FDA before they can be marketed.