Sound Advice About Age-Related Hearing Loss

FDA Consumer magazine
May-June 2005 Issue
Pub No. FDA05-1340C

This article contains revisions made in September 2005.

The popular notion that older people are "hard of hearing" is often true. Hearing loss occurs gradually in most people as they age.

According to the National Institute on Deafness and Other Communication Disorders (NIDCD), part of the National Institutes of Health, about 1 out of every 3 U.S. adults between the ages of 65 and 75 has a hearing loss. The NIDCD further estimates that about half of people 75 and older have some degree of hearing loss.

"We are born with a set of sensory cells, and at about age 18 we slowly start to lose them," says Hinrich Staecker, M.D., Ph.D., director of the otology and neurotology program at the University of Maryland Medical Center in Baltimore. But because age-related hearing loss, called presbycusis, progresses so slowly, most people don't notice any changes until well after age 50.

There are exceptions. Nancy McKinney was in her 40s when she was diagnosed with mild, age-related hearing loss. Now 51, the college English professor from Taylorville, Ill., remembers that she kept telling her students in her classes to speak up. She also recalls constantly turning up the volume on her TV. Hounded by family and friends, McKinney eventually sought the advice of one type of hearing specialist--an otolaryngologist.

"My family was driving me nuts," she says. "But the main thing was I knew that I couldn't hear." Because her hearing loss was mild, she was told that she did not need a hearing aid at that time.

Presbycusis, which the NIDCD says usually affects both ears equally, is most commonly caused by gradual changes in the inner ear. As people age, structures of the ear can become less responsive to sound waves, contributing to hearing loss. Staecker says that early, undetected hearing problems can compound hearing loss brought on naturally by aging.

Hearing problems can make it difficult for older people to hear doorbells, car horns, and alarms. Hearing loss also can make it hard to understand and follow a doctor's advice or respond to warnings. Its effect on speech communication can reduce a person's physical, functional, emotional, and social well-being. Isolation and depression often accompany hearing loss. All of this can be frustrating, embarrassing, and even dangerous.

Without being aware of it, people with presbycusis may make small adjustments over time, for example, standing closer to someone who is speaking or turning up the TV volume, that allow them to perceive the sounds and cues they otherwise would miss. At some point, though, the loss may become so severe that these adjustments become ineffective.

The good news is that there are ways to compensate for age-related hearing loss. There are devices to help people hear and communicate more easily, including hearing aids and assistive listening and alerting devices, such as telephone amplifiers. If you have trouble hearing, visit your doctor or hearing health care professional to find out if you have a hearing loss and, if so, how to treat it.

The Food and Drug Administration regulates hearing aids and other devices used to prevent, diagnose, and treat hearing loss to ensure that they are safe and effective. But the agency also hopes people will help themselves by protecting and caring for their ears.

From Sound Waves to Brain Waves

To better understand hearing loss, it helps to know how people hear the sounds around them. According to the NIDCD, people don't just hear through their ears--they hear with their brains. A vibration, which can be transformed into the sound of a moderate rain, a rock lyric, or the blast of a chainsaw, is first picked up by the ears and then "read" by the brain.

The ear is made up of three parts: the outer ear (pinna or auricle), the middle ear, which includes the eardrum (tympanic membrane), and the inner ear (cochlea), which is shaped like a snail shell and lined with tiny hairs.

Hearing loss occurs when the tiny hairs inside the cochlea are damaged or die, a common occurrence as people age. Hair cells, which pick up sound waves and transform them into nerve impulses, do not regenerate. That's why most hearing loss is irreversible.

Sound enters the outer ear and strikes the eardrum, causing it to vibrate. The eardrum's vibrations are amplified through the chamber of the middle ear along three tiny interconnected bones, named for their shapes--hammer (malleus), anvil (incus), and stirrup (stapes)--which pass on the vibrations of sound waves to the cochlea.

The brain interprets the nerve impulses from the cochlea as the ring of a doorbell or telephone, words being spoken, or the honk of a car horn. The combination of pitches, or frequencies, give different sounds their distinctive qualities. The brain also uses the source and direction of the sound and loudness as clues to decipher messages.

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.

Types of Hearing Devices

Hearing aids are tiny instruments worn in or behind the ear that amplify sounds in people with either conductive or sensorineural hearing loss. Some need a hearing aid for only one ear. Others need one for both. A health care professional will determine whether you need one or two.

Hearing aids have different electronic characteristics that are chosen to suit the person's particular type of hearing loss. For example, people whose hearing loss affects mainly higher frequencies do not benefit from simple amplification, which merely makes the mumbled speech they hear sound louder. Hearing aids that selectively amplify the high frequencies markedly improve speech recognition. Other hearing aids contain vents in the ear mold--a specially molded piece of Lucite or vinyl material that fits inside the device--which facilitate the passage of high-frequency sound waves into the ear.

Staecker says different hearing losses respond differently to treatment with hearing aids. He describes people's hearing as similar to listening to a radio. "Certain hearing losses are like having the volume knob on the radio turned down. When you increase the volume on your radio from very low to audible, information is heard more clearly," he says. "In other losses there is a volume problem and a reception problem. If the station you are listening to is not tuned in clearly, no matter how much you increase the volume, the information coming from the radio will not be clear." These types of hearing losses, he adds, do not necessarily respond well to hearing aids.

Many hearing aids use digital sound processing with multiple frequency channels so that the amplification can even more precisely match the person's hearing loss. But Eric A. Mann, M.D., Ph.D., chief of the FDA's Ear, Nose, and Throat Devices Branch, says that some of these devices may not be suitable for older people, who might find it difficult to manage the small, often complex components. People who cannot tolerate loud sounds may need hearing aids with special electronic circuitry that limits the maximum volume of sound to a tolerable level.

Here are some of the most common types of hearing aids and their advantages and disadvantages:

People who sell, lease, or rent hearing aids have certain obligations to their customers. Federal rules require that people visit a doctor to rule out a medical problem before being fitted for hearing aids by a licensed hearing aid dispenser. The FDA does allow people to buy hearing aids without a medical exam--for example, because of religion or personal beliefs--if they sign a waiver provided by the hearing health care specialist at the time of the purchase. Dispensers should not encourage people to waive their right to a medical exam, however, and must advise them that it is not in their best interest to do so.

In practice, Mann says that many people waive the requirement. The result, like for McKinney, is that they are not properly evaluated and fitted before they buy and use hearing aids. "Unfortunately, consumers may fail to have diagnosed a medically treatable cause for their hearing loss--something as simple as a wax buildup or as serious as a tumor of the hearing nerve," he says.

Hearing aids sold through the mail must also meet FDA regulations. Kane, who reviews hearing aid devices at the FDA, advises people to adopt a "buyer beware" posture. He says that it's important for people to have a medical clearance before buying a hearing aid through the Internet. "It makes sense. A doctor's referral will help people find a certified, legitimate hearing aid dispenser that they can rely on."

Kane also says that "auditory rehabilitation is more than just purchasing a hearing aid." Appropriate counseling from a professional is critical for success with amplification. "Purchasing over the Internet precludes this important rehabilitation component," he says. The patient's spouse and family members also need to be counseled about the expected limitations and the benefits, because they are a part of the person's communication environment.

Prices of hearing aids vary considerably, depending on the technology. Staecker, who regularly refers people for hearing aids, says to get a second opinion when comparing the price and features of hearing aids.

As for mobile phones, laboratory testing of more than 20 hearing aid models found that those tested were susceptible to interference from the digital cellular phones that are now used in the United States. In general, behind-the-ear hearing aids experienced higher levels of interference than in-the-ear devices. Currently, a testing standard is being developed that will allow consumers to see ratings of the "compatibility" of specific combinations of mobile phone and hearing aid models. People should ask their dispensers for more information on mobile phone use and the type of hearing aid they are interested in.

Mann adds that the Federal Communications Commission has recently required that wireless phone manufacturers and wireless service carriers must make digital wireless phones compatible with hearing aids within the next five years.

It may take several weeks or months for a person to learn to interpret the new sounds from a hearing aid, and there is great variability in the results. Many hearing aid manufacturers offer trial rental or purchase option plans--usually up to 30 days--to allow their customers to judge the product's effectiveness and benefits. Check with your state health department to find out about the regulations covering trial periods for hearing aids. Kane says that some states have special licensing divisions within the larger health department.

People with severe to profound hearing loss who aren't helped by hearing aids may benefit from a cochlear implant. This is an electronic hearing device that is surgically implanted behind the ear, with wires and electrodes inserted into the cochlea and a microphone and transmitter that are worn outside the body. It is designed to produce useful hearing sensations by electrically simulating nerves inside the inner ear. Although a cochlear implant can't restore normal hearing, it can help a person hear sounds and distinguish between them.

Implantable middle ear hearing devices are designed to restore some hearing by vibrating the tiny bones of the middle ear in people with mild to moderately severe sensorineural hearing loss. The person must have a healthy middle ear, but may opt for an implant simply because they do not want to use conventional hearing aids. The advantage of this device over a conventional hearing aid is that it is not dependent on simply amplifying sound, as is a hearing aid.

Auditory brainstem implants are intended to restore useful hearing in people who experience total hearing loss when the removal of tumors damages their cranial hearing nerves. The device restores the ability to detect certain sounds and speech, although it does not restore normal hearing. It is surgically implanted into the brain and electrically stimulates the area that normally receives the electrical signal from the ear. The patient wears a pocket-sized speech processor that picks up sound and changes it into electrical pulses that are transmitted to the implant.

Some Won't Hear Of It

Doctors know that hearing aids, telephone amplifiers, and medical evaluations can help individuals with hearing impairment avoid social isolation and other problems associated with hearing difficulties. However, Mann says these options are not being used by the majority of older people who could potentially benefit--perhaps out of embarrassment, because the hearing loss is under-diagnosed, or because it is under-treated.

"Some people perceive that there is a social stigma associated with wearing a hearing aid," he says. Many people who have a hearing impairment are afraid to admit it, or are unaware of the sophisticated communication devices available to improve their hearing. Mann says that many people have unrealistic expectations and are disappointed in the performance of their device. "Most everyone knows a relative or an acquaintance who has purchased a hearing aid that now sits in a dresser drawer," he says.

Mann also cites a significant financial investment in many cases, and associated with this is the risk of ownership. People are worried about losing or damaging a high-priced investment, he says. And there is also some inconvenience on the consumer's part with the traditional route for obtaining a hearing aid--multiple visits, hearing aid evaluations, medical evaluations, and follow-up visits to address specific problems, such as feedback and comfort issues with the ear molds. "In some cases," Mann says, "there may be trust issues with hearing aid dispensers based on a history of unethical business practices with some companies in the past."

But the hearing health care profession agrees that all of these obstacles can be overcome. Many organizations exist to provide people with advice and information, and there are professionals who are willing to work with older people to help them overcome their fears and concerns.

As for McKinney, she still asks her students to speak up and sometimes turns up the volume on her TV when it doesn't inconvenience other family members. But, she says, "How bad does your hearing have to be before you do something about it?" In her case, it's no worse than it was initially. "I'm not embarrassed about the fact that I may need to wear a hearing aid one day," she admits. But the next time she tries one on for size, she says she'll first have a medical evaluation and then be referred to a reputable hearing aid dispenser for a proper fit.

The Mechanism of Hearing

Our ability to hear depends on a complex series of events. The outer ear ends at the eardrum. Three tiny bones called the auditory ossicles transmit vibrations from the eardrum to the oval window, which separates the middle ear from the inner ear. In the fluid-filled inner ear is the cochlea. The organ of Corti, located within the cochlea, contains hair cells that detect the vibrations and produce electrical signals. Nerves carry these signals to the brain, where they are interpreted as sounds.

How to Lessen the Severity of Age-Related Hearing Loss

How Loud Is Too Loud?

Noise is measured in units called decibels, on a scale from zero to 140. The higher the number in decibels, the louder the noise. The louder the noise, the greater the risk of hearing loss. Hearing loss can occur with regular exposure to noise levels of 110 decibels or more for periods longer than one minute. No more than 15 minutes of unprotected exposure to 100 decibels is recommended.

Hearing Health Care Professionals At a Glance

Otolaryngologists (M.D. or D.O.) are licensed physicians who specialize in diseases of the ear, nose, and throat (ENT), and are medically trained to identify the symptoms of deafness in context with a person's overall health. They are qualified by special training to diagnose and treat hearing loss and related structures of the head and neck. They are commonly referred to as ENT physicians.

Otologists (M.D. or D.O.) and Neurotologists (M.D. or D.O.) are highly specialized otolaryngologists knowledgeable in the basic sciences of hearing, balance, nerve function, infectious disease, and anatomy of the head and neck. They also may manage diseases and disorders of the cranial nerves and skull base.

Audiologists are qualified by training and experience to specialize in evaluating and rehabilitating people whose communication disorders center around hearing. They must hold at least a master's degree in audiology from an accredited university. In some states, audiologists must satisfy specific requirements to be licensed.

Hearing aid dispensers are people, partnerships, corporations, or associations that sell, lease, or rent hearing aids to the public. Individual dispensers must be high school graduates who have completed at least six months of training under a licensed hearing aid dispenser. They must pass both written and practical state examinations.

Buyer Beware!

Sorting help from hype in any media--television, print, or the Internet--can pose a problem. So remember, if a claim sounds too good to be true, it probably is. Here are some points to remember when considering a hearing aid:

For More Information

American Academy of Otolaryngology--Head and Neck Surgery
www.entnet.org
(703) 836-4444