David M. Kaylie, MD, FACS
Duke University Medical Center
Otolaryngology – Head and Neck Surgery

Benee Connelly, AuD
Duke Otolaryngology of Raleigh

Hearing Loss

Hearing impairment is very common – it affects 10% of all Americans.

Two million are deaf and 26 million have some degree hearing loss (over half of these are 65 or older). With an aging population, the problem of hearing loss will only become greater.

The cost of hearing impairment is $56 billion annually -- 50 percent higher than the cost of visual impairments. The high cost comes from everything from disability payments to missed work days.

Worldwide, the problem is even worse: China and India are in a dire situation with a disproportionate number of deaf people because of poor access to medical care and frequent use of toxic antibiotics, or those that cause hearing impairment.

Hearing loss is a major problem that will affect most people at some point – including yourself or a loved one. A large population in the US will go untreated or remain unaware of their treatment options, so public education is key to understanding hearing health.

How Do We Hear?

The ear is comprised of the ear canal, ear drum, hearing bones (ossicles), and the inner ear. These parts work together to make up the two kinds of hearing that we have: conductive and sensorineural.

Sound is collected by the outer ear and which sends the waves down the ear canal to the ear drum. As the ear drum vibrates, the three hearing bones (commonly known as the hammer, anvil, and stirrup) begin to vibrate. The third bone, the stirrup, stimulates the inner ear.

When the third ear bone moves, it moves in and out like a piston, in the cochlea, which is the hearing part of the inner ear. The spiral-shaped cochlea is filled with fluid that conducts the sound wave up and then back down.

The cochlea is arranged sort of like a guitar, where the top of it is responsible for picking up the lowest sounds and the bottom picks up the highest tones. (So the waves travel to both areas to make sure all tonal range is picked up)

The inner ear has nerve cells, called hair cells, that bend as the sound wave travels by – which in turn triggers the nerve to fire. Most hearing loss is caused by something that has damaged the hair cells – normal aging, noise, and some medications can all damage hair cells.

Types of Hearing Loss

There are two main types of hearing loss:

• Conductive: The sound never makes it to the inner ear, due to impaired sound transmission in the ear drum, middle ear, or ossicles. This could be from a hole in ear drum from injury or infection, fluid in middle ear (prevents ear drum from vibrating) from allergies, cold or infection, trauma to bone from otosclerosis (a condition where the third hearing bone starts to fuse to the bone around it and it can no longer make the piston-like movement it needs to), trauma, or congenital defect.
• Sensorineural: Everything functions normally in the hearing canal, but for some reason there is a disconnect in the nerve or the brain and the sound waves are not processed as sound.

Presbycusis: Adult Hearing Loss

Presbycusis is the normal hearing loss that occurs with aging. It is the most common form of sensorineural hearing loss and will affect half of people over the age of 75. Men are affected twice as often as women.

The symptoms of adult hearing loss are slowly progressive hearing loss, usually in both ears; and ringing in the ears (tinnitus) which is a sign of nerve damage – usually occurring in both ears and presents with a variety of tonal qualities.

The causes of presbycusis include:

• Noise – exposure to noise can damage the nerves, leading to hearing loss. This is worse in industrialized nations and affects men and women equally.
• Heredity/genes – if there is a family history of hearing loss, you may be more at risk
• Degeneration – aging causes nerve degeneration, which presents as hearing loss

Getting Evaluated

All hearing loss should be evaluated by an ENT doctor. He will look for common problems that can cause hearing loss, but which exclude true hearing loss:

• Mini-strokes that have temporarily damaged the nerves
• Inner ear infection which leads to a feelings of deafness and dizziness
• Drugs that may cause hearing loss, including those used in chemotherapy

An ENT will also perform a thorough hearing test to determine exactly what kind of hearing loss you have.

Preventing Hearing Loss

The best ways to prevent hearing loss are:

• Avoid noise – even small amounts of loud noise can cause hearing loss.
• Wear protection – use earplugs or earmuffs to protect your ears in noisy situations
• Discontinue damaging drugs if possible.

There is no surgery or medicine that can treat nerve-related hearing loss, so we must rely on amplification and assistive devices.

Chronic noise exposure causes a very typical pattern of hearing loss. Someone with hearing loss has trouble hearing speech over background noise -- all they can hear is background noise.

Hearing loss in just one ear really needs to be evaluated – causes can just be conductive hearing loss because of infection, otosclerosis, hole in drum, or middle ear fluid.

People who have nerve hearing loss in only one ear have asymmetric neural hearing loss – the vast majority of the time it’s just how you are, but it could be also a tumor (acoustic neuroma), or it could be the result of a stroke or multiple sclerosis.

Hearing Loss that Requires Immediate Attention

• Sudden hearing loss that occurs very rapidly, from one day to the next
• Rapidly progressing hearing loss that worsens over several days or weeks
• Hearing loss with pain
• Hearing loss with dizziness

How to Choose the Right Hearing Aid

A 2006 duke study showed that effects of hearing loss include depression, strained relationships with family and friends, and deterioration of basic well being. In addition, 26 million Americans have hearing loss, but only 20 percent who could benefit from a hearing aid actually have one.

All hearing aids have four basic components:

• Microphone
• Amplifier
• Speaker
• Battery

Hearing Aid Styles

• CIC (Completely in Canal) – These are the smallest of all the hearing aids, fitting deeply into the ear canal. They are best suited to mild or moderate hearing loss. While they are cosmetically appealing, they are more prone to feedback, have higher repair rates, and the batteries are so small that patients with vision or dexterity issues have problems handling them.
• ITC (In the Canal) – This aid is a little larger than the CICs but has all the same problems and considerations.
• Full-Shelf Aid – This is a much larger aid, taking up most of the bowl portion of the ear – but it can accommodate many more options.
• BTE (Behind the Ear) – This is the largest aid, sitting behind the ear. It is coupled to an ear mold, which channels sound directly into the ear. It is very flexible, easiest to adjust and can be fit to any type of hearing loss. It works especially well in situations where people have high frequency hearing loss.

Do All Hearing Aids Work the Same Way?

No. Ten years ago you had analog aids only, which are currently being phased out – they converted waves into electrical signals but amplified everything equally instead of distinguishing between sounds.

Digital hearing aids are today’s aids – they come in many price points, and are superior in quality, programming and features or options. They translate sound to digital code – so the manufacturer can write specific programming software to be used in certain situations. A digital hearing aid analyzes and adjusts sounds based on your level of hearing loss and listening needs. It also producse high quality sound that is extremely accurate, clear and distortion free.

Special features available on digital aids include:

• Directional microphones – allow you to hear sounds that originate in front of you more clearly than those behind
• Feedback and noise reduction – better at reducing background noise
• Automatically adaptive – multiple programs or settings that may activate noise reduction with directional microphone
• Bluetooth compatibility

Do I Need Two Hearing Aides?

Yes. If you have loss in both ears two aids provide for a more natural perception of sound. They will provide better understanding in background noise, make it easier to determine the direction of the sound, and will slow deterioration of hearing.

Hearing aids will not restore hearing to normal, nor will they prevent further decline, but can provide substantial benefit.

What Is the Best Hearing Aid?

The best hearing aid is not the smallest, least expensive, or most invisible. You should pick one that suits your needs and lifestyle – what are your listening needs, what type of hearing loss do you have, how severe is your hearing loss. And, style and features do affect cost.

Things to Consider

• Watch out for scams
• Check your insurance – not many cover the cost, but some do
• Veterans Administration benefits – if you believe hearing loss is due to military service, check with your VA
• Vocational rehabilitation – if hearing loss is preventing your employment, you may qualify for help
• Learn about overcoming hearing loss
• Learn about hearing aid features

Who Is Qualified to Conduct a Hearing Test?

The only people qualified to conduct a hearing test are a physician or ENT, an audiologist, a technician, or a hearing instrumentation specialist.

Audiologists are required to be licensed by the state. They must have doctoral degree, proof of 90 clock hours in university study, and 1800 hours of supervised time on the job.

Hearing instrument specialists must have at least a high school diploma and have worked at least 30 hours per week for 50 weeks in the setting of sale and fitting of hearing aids. They also must document that they have been supervised for 750 hours on the job.

The FDA restricts the sale of hearing aids to those who have received a proper medical evaluation. Your audiologist is required to have documentation of the evaluation prior to selling you a hearing aid.

Questions to Ask Your Audiologist

• What features would be most helpful to me?
• What is the total cost?
• Is there a trial period?
• What fees are nonrefundable if the aids are returned after the trial?
• How long is the warranty and can the warranty be extended?
• What are the deductibles for loss and damage?
• Can adjustments and minor repairs be made by the audiologist?

Tips for Success

• Use the trial period wisely! Test drive your hearing aids in different situations and keep a log of the results.
• Take care of your investment – this includes frequent cleaning and trips to the audiologist for tune-ups.
• Accept your hearing aids – your hearing aids are less conspicuous than your hearing loss.

More Information

NICD Information Clearinghouse
1 Communication Avenue
Bethesda, MD 20892-3456

Voice: 800-241-1044
TTY: 800-241-1055
Email: nidcinfo@nidcd.nih.gov

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