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HEARING AIDS

Timothy C. Hain, MD

Hearing aid index Page last modified: March 21, 2014


Hearing aids are electrical devices that assist perception of speech or other sounds. We are generally in favor of hearing aids in persons with significant hearing loss. We think that life is too short to have a suboptimally functioning sense.

WHO NEEDS A HEARING AID ?

In essence, you need a hearing aid if the cost/benefit ratio is reasonable. An "ideal" hearing aid candidate is someone with a mild-moderate bilateral hearing loss, and who has experienced a noticeable communication handicap. Many individuals who have good hearing on one side can adjust reasonably well to any degree of hearing loss on the other side. Hearing aids are not indicated for an ear with minor hearing loss, and are also not very useful in an ear with profound hearing loss. In other words, hearing aids are usually most appreciated in people with mild to moderate hearing loss on both sides.

Be sure that you need a hearing aid. It is said that 2/3 hearing aids go unworn. Most states have a 30 day return policy.

SITUATION USUAL BENEFIT
Minimal or no hearing loss, or steep drop. Minimal or no benefit (little to gain)
Moderate hearing loss Good benefit
Profound hearing loss Minimal or no benefit from conventional aid, consider cochlear implant if bilateral, BAHA if unilateral.

An example of an audiogram where a hearing aid is probably not going to help because of a steep drop is shown below.

Steep
A hearing aid will likely go "in the drawer" for a person like this. There is a very steep drop between 1-2K, and at higher frequencies, hearing is severely impaired.

The problem here is that there is only a small range of frequencies where making sound louder will help (between 1-2K). Making things louder at higher frequencies will cause distortion and feedback. This patient does not need anything louder at lower frequencies, so benefit is minimal.

Could a hearing aid or hearing assistive device make hearing worse ?

This is a complex question that has been debated since the 30's. Essentially the idea is that hearing aids make noises louder, and it is well known that loud noise can cause hearing loss. Macrae dealt with this issue in a rigorous fashion (Macrae, 1991; 1995). The abstract of his 1991 paper states "The model implies that any noise exposure that would cause deterioration of the hearing threshold levels of a person with normal hearing would also be harmful to the hearing of a person with sensorineural hearing impairment. It follows that, in order to ensure that no deterioration occurs in the hearing of a hearing aid user, the output levels from the aid must be such that they would not cause any damage to a person with normal hearing. This constraint can be met for hearing aid users with mild-to-moderate sensorineural hearing loss but cannot be met for users with severe-to-profound loss because it would result in the provision of insufficient gain, particularly at the higher frequencies. If the model is valid, then for this group, some appropriately small amount of hearing damage must be accepted as the cost of the advantages gained from the use of a hearing aid."

In spite of this theoretical prediction, the literature does not bear out a substantial effect. For example, Podoshin and associates (1984) reported hearing results over 8 years in 114 patients aged 10 to 91 years with different kinds of hearing aids fitted in one ear only, the unaided ear acting as a control. There was no change in hearing between the aided and the unaided ear at least for 8 years.

Our take on this issue is that logically, there must be a risk of a hearing reduction from loud noise, including that produced by hearing aids, and that one should consider the (small) risks and benefits when purchasing one of these devices. To be safe, hearing aids or assistive devices should have circuitry that limits output to safe levels.

CAN HEARING AIDS IMPROVE WORD RECOGNITION THROUGH CENTRAL REORGANIZATION (ACCLIMATIZATION) ?

Some have suggested that hearing aids can improve word recognization through central reorganization.  Song et al (2011), recently studied this issue and suggested that there is no such improvement. Similarly, Maniakas et al (2014) showed there was no difference in hearing between individuals who were treated for otosclerosis early on or 10 years later. These data suggest that the idea that your hearing will deteriorate unless you buy a hearing aid is just marketing hype.

WHAT TESTS ARE NECESSARY BEFORE SELECTING A HEARING AID ?

Audiometric evaluation -- determine type (i.e. sensorineural, conductive or central), degree, and frequency slope. Determine word recognition score with and without amplification. The evaluation should be able to predict the amount of benefit of a hearing aid, in terms of speech comprehension. Many times an office may have a unit that you can try in the office. While this will not be as good as a custom fitted hearing aid, it will give you an idea whether or not it is a good idea to proceed.

Otologic evaluation -- determines whether medical or surgical treatment is possible (i.e. wax removal). Approximately 5% to 10% of adult hearing problems are medically or surgically treatable. The percentage is higher in children if middle ear disease, such as ear infection, is the cause(http://www.asha.org/public/hearing/treatment/hearing_aids.htm)

Medical clearance is advisable before purchasing a hearing aid.  We have encountered individuals who were fitted with a hearing aid, not knowing that they had a tumor of the hearing nerve.

TYPES OF HEARING AIDS

Organized by technology (and expense)

  1. Analog. There are several circuits.
    1. Linear peak clipper (least favored in VA study, Larson et al, 2000)
    2. Compression limiter (preferred in VA study)
    3. Wide dynamic range compressor (2nd best in VA study)
  2. Simple programmable. Longer fitting time and follow-up.
  3. Complex programmable.
  4. Digital. Flexible but expensive.
  5. BAHA -- bone anchored hearing aid. Good for persons with one good ear and one bad ear.
  6. Cochlear Implant (see below). Very expensive, for bilateral acquired deafness.

Special features include directional microphones (CPD), noise reduction algorithms, loudness scaling, and multiple listening "programs", remote control options, "high resolution" auto-controls, speech enhancement algorithms, and feedback controls.

Desirable characteristics are:

Organized by appearance and size

Assistive listening devices. A large variety of devices are available at much lower cost than hearing aids. Some are free. Telephone companies provide free amplifiers and ringers if patients present a physician or audiologist release. Hotels provide telephone amplifiers in 10 percent of rooms. Examples are devices that flash lights when the telephone rings, vibration devices when the doorbell sounds, flashing smoke alarms, television amplifiers, etc.

Hearing aids:
Behind the ear (BTE). Cheapest, easiest to adjust, less feedback than other devices. Fairly visible (the model shown in the middle is from the Oticon web site). Most powerful. Fewest number of problems with wax or infections. Does not require an impression. BTE hearing aids come in many different colors to match your skin, hair, and bright colors for kids. They may be connected to external sound sources such as assistive listening devices (directional technology, FM systems, CROS/BI-CROSS hearing devices) and telephones and televisions using a t-coil.
Post-auricular canal (PAC). A hybrid between BTE and CIC. Almost invisible, easy to fit and maintain. The pictures are from Sebotek.
In the ear (ITE).  Low visibility; harder to put in than PAC or BTE. Powerful and still fairly easy to adjust. This type of hearing aid is custom made to sit flush with your outer ear and yet still is easy to manipulate. ITE hearing aids also come in skin colors and can also be equipped with directional technology and t-coils.
In the canal (ITC). Very low visibility. Clearer than BTE. Lower power so not suitable for persons with more severe hearing problems. Patients with tremor or poor eyesight are not good candidates. ITC hearing aids are also matched to skin color.
Completely in the canal (CIC). This is the smallest hearing instrument available today. Patients with tremor or poor eyesight are not good candidates for the CIC. It is best used for mild to moderate hearing losses. It fits snugly into your ear canal with a tiny filament that is used to remove the instrument. The outer surface of the CIC is made to match skin color.

There are also Body/Eye-glass styles (< 1% of all hearing aids), low-profile, half-shell, and canal types.

The PAC type hearing aids are particularly simple -- very little fitting is needed -- no ear mold, and can practically be used "off the shelf". Of course, they should be "equalized" for the hearing deficit that the patient has. This "equalization" process requires someone to have equipment that "talks" to the digital hearing aid. It seems to us though that most people could do this themselves if they had an interface to their hearing aid, such as an "app" for their smart phone.

Binaural/Monaural

Advantages of Binaural hearing aids

Binaural amplification means hearing aids on both sides. If you have trouble with hearing on both sides, this is obviously better than one side only, but more trouble to keep maintained. Binaural amplification minimizes impact of "head shadow" drop off, improves sound localization, widens dynamic range, and costs twice as much. Some individuals with bilateral hearing impairment do worse with two aids than one. This usually happens when the ears differ appreciably in hearing impairment, and occurs because the noisy/distorted/louder input from the poorer ear interferes with hearing from the better ear (i.e. binaural interference, see Baron, 2002). Nevertheless, most people with age related hearing loss opt for binaural hearing aids.

Bells/Whistles

There are some very nice technologies that you can use with your aid. T-coils and FM systems are methods of getting very clear sounds with no feedback. You should investigate these if you are OK with wearing a larger hearing aid.

 

Hearing aids for people who are deaf in one ear

  1. CROS aids --aid on one side "pipes" sound to other side, where hearing is better. Most hearing aid users are unenthusiastic about CROS aids, but recent improvements in technology has made them much better (use of digital and wireless technology) There are three types of CROS aids:
    1. Wired CROS -- while effective, the wire connecting one ear to the other can be annoying.
    2. Transcranial CROS -- This is only possible in people with one entirely dead ear
    3. Wireless CROS -- more convenient, vulnerable to electrical interference
  2. BAHA -- bone-anchored hearing aid. While it can be used like a conventional hearing aid, usually it is used in people who have good hearing on one side and no hearing on the other -- thus it is a surgically implanted version of the CROS aid. Most people with unilateral hearing loss are enthusiastic about BAHA aids because it works very well and it is unobtrusive. It requires "very good" hearing on the opposite side. It eliminates the head shadow effect, occlusion effect, and feedback.
BAHA (bone anchored hearing aid). This type of hearing aid works well in persons with severe unilateral hearing loss. The image to the left, from Prosper hospital, shows how a button is inserted into the bone of the skull above the ear. The middle image is from Island Hearing. The device is attached to the button within the skull. It is very unobtrusive (once the hair is put back into place).

How much do hearing aids cost ?

Hearing aids are typically not covered by Medicare or commercial insurance and pricing varies according to the manufacturer, vendor, and service arrangements. According to Kirkwood (2005), in 2004, the average price of a hearing aid was $1776. These prices are taken from an article on management of hearing loss by Bogardus et al, 2003.

Hearing Aid Type One ear Both Ears
Conventional (Analog, non-programmable) 850 -1500$ 1400-3000
Programmable (Analog) 949 -2000$ 2200-4000
Digital 1399 -2999$ 4200-5400

There are numerous brands and variants. In general, smaller devices, such as the CIC devices mentioned above, are more expensive, and newer/more complex circuitry is also more expensive. Compression circuitry in analog aids is more expensive (but definitely a good idea). Directional microphones cost more, but are also a good idea. Greater user control is also usually more expensive. Bilateral aids are often but not always better (Baron, 2002).

Hearing aids are overpriced.

Hearing aids are very expensive and many people choose not to use them because they can't afford them. Bainbridge et al reported that a 28 to 66% greater prevalence of hearing aid use among more affluent older adults (2014). Although we do not know of any published data on this, the "real" cost of a hearing aid -- which is similar in electronic complexity to an ipod, is probably roughly a tenth of the "offered price" world wide. It has been explained to us that hearing aids are special because one buys not only the hearing aid electronics but also bundled maintenance services for several years. Nevertheless, consumers have no choice regarding the bundled services. We suspect that allowing competition could result in hearing aids priced like ipods.

In Illinois where we practice medicine, as well as in many other states, there is a 45 day tryout period for hearing aids, which is a legally mandated money-back guarantee for the hearing aid. The dispenser is allowed to keep a reasonable fee for their services during the trial (which can be substantial). This is a good law that protects the hearing impaired population, many of whom are older and may be vulnerable. Additionally, "hearing aid clearance" is required, meaning that a physician needs to authorize the dispensing of a hearing aid.

As hearing aids are generally not covered by insurance and typically cost in the $1000's, we recommend that you think about purchasing one carefully. On the other hand, hearing is a very important sense and you can be oblivious to much important information as well as very annoying to your family when you can't hear.

Some suggestions for persons who can't afford a hearing aid are here.

Who dispenses hearing aids ?

There are many ways to obtain a hearing aid. The most common method is to visit a dispensing audiologist who can test your hearing, recommend an appropriate device, and assist in the maintenance. Legally, hearing aids can be dispensed by licensed physicians, licensed audiologists, and licensed hearing aid dispensers. Dispensing law requires a medical clearance for hearing aid use by a physician (meaning that the ear canal is clear although a waiver is allowed for users over 18 years old).

There are some web-sites that offer hearing aids such as hearingplanet, and remoteaudiology. These businesses generally require you to see a hearing professional to get a hearing test done as well as an impression made (to customize the aid to the configuration of your ear). This may cost less than finding a dispensing audiologist. Hearing aids are also sold in department stores (such as Costco) as well as in other venues, again typically at a discount compared to dispensing audiologists.

We think that it is best to find a reputable source for your hearing aid, and also a source that will offer a reasonable selection of devices. An office that offers both a physician evaluation as well as an audiologist is best -- we have encountered people fitted with a hearing aid that actually had a tumor on the auditory nerve. Usually this kind of mistake can be avoided with physician oversight.

Advances needed in hearing aids

Over the last few decades, the big push with hearing aids has been to make them smaller. This has been accomplished rather well, and we think that the next big push needs to be in improving performance. Features that we would love to see routinely in hearing aids are the following:

Where to get a hearing aid.

We think that, for the most part, people looking for a hearing aid should find a dispensor that is close enough to them that they can easily get their hearing aid serviced, cleaned and checked. In more rural areas where parking and traffic is less intense, larger distances seem reasonable. You should consider how far the office is from your house or place of work as return visits may be required for cleaning and repair.

Cochlear implants and other implantable devices

An exciting recent development is an ability to provide hearing to some bilaterally deafened individuals through implantation of a device which directly stimulates the hearing nerve (actually the spiral ganglion). Although this device is not generally considered as a "hearing aid", it performs the same purpose for individuals with severe hearing impairment involving both ears. For more details, see the cochlear implant page.

REFERENCES

Copyright March 24, 2014 , Timothy C. Hain, M.D. All rights reserved. Last saved on March 24, 2014