INTRODUCTION — Devices that amplify sound are integral to the management of hearing impairment. These include hearing aids, amplified telephones, and portable devices that can be used to amplify the sound coming from electronic systems at public events. Implantable hearing devices (eg, cochlear implants, osseointegrated implants, and electrically driven middle ear implants) are integral in providing hearing for adults in whom traditional hearing amplification devices do not provide adequate hearing.
Hearing amplification devices for adults are discussed here. Hearing amplification devices for children and the differential diagnosis and evaluation of hearing loss in adults are discussed separately:
HEARING AIDS — Most hearing impairments can be helped with a modern hearing aid. Young, middle-aged, and independent older adults who have hearing difficulties that interfere with work and social interactions, and who are highly motivated to improve their hearing, make excellent candidates for hearing amplification . Hearing aids improve hearing-specific health-related quality of life, general health-related quality of life, and listening ability in adults with mild to moderate hearing loss . A comparison of hearing aid types is available in the table (table 1).
Identifying appropriate candidates — The first step in providing hearing amplification is for the audiologist, referring clinician, and patient to agree that the patient needs and is likely to benefit from a hearing aid. This mutual decision is based upon:
●The audiogram results – Typically, a minimum hearing loss of 10 decibels (dB) over two to three frequencies is required for consideration of hearing amplification.
●A specific hearing difficulty assessment – Patients with poor results on audiometric word discrimination testing might not achieve significant benefit from a hearing aid. The method of testing a patient’s hearing has evolved; the traditional soundproof testing room did not approximate a “real world” environment and poorly assessed a patient’s true ability to hear. Thus, the addition of background noise is now used to test a patient’s ability to hear and understand words and sentences. (See "Evaluation of hearing loss in adults", section on 'Speech audiometry'.)
●The patient's lifestyle.
●The patient's motivation level.
●A realistic discussion about what a hearing aid can and cannot do. One common misconception is that the aid restores normal hearing just as corrective lenses restore normal vision. Hearing aids do not restore hearing to normal. As a general rule, a hearing aid usually improves hearing by one-half of the loss. As an example, a patient with a 60 dB hearing loss could expect to hear in the 30 dB range with hearing amplification. Thus, the goal of hearing amplification is not to restore normal hearing, but to significantly improve communicative ability and quality of life.
Advanced age is not a factor; in a study of patients with reduced hearing, the use of digital hearing aids led to equivalent improvement in speech performance among those over age 80 years compared with those ages 65 to 80 years .
Unilateral or bilateral hearing aids — Binaural fitting provides the most benefit, including balanced hearing, sound localization, directional hearing, better speech understanding, and better hearing in noisy situations [4-7]. Binaural fitting may not be successful in patients with large hearing asymmetries, or if caring for two hearing aids would be difficult. Patients with financial constraints may benefit more from two simple hearing aids than one more complex device. One hearing aid may be sufficient when hearing loss is minimal, but even patients with unilateral hearing loss should be fitted with a hearing aid, because bilateral hearing is important.
Cosmetic and other issues — Most patients would like to avoid anyone knowing that they wear a hearing aid and thus commonly ask for the mini, completely in the canal, or in-the-ear type aids.
However, not all patients are candidates for this small device. In patients with severe or even significant moderate hearing losses, a behind-the-ear hearing aid may be necessary in order to generate enough power to facilitate better hearing. Additionally, smaller devices will offer fewer features because of size limitations .
Open-mold hearing aids are popular for their non-occlusive fitting and improved performance for high-frequency loss compared with traditional aids. These aids are also small.
Electronic capabilities — Hearing aids have differing levels of electronic features. Options include digital or analog compression, and some hearing aids are programmable while others are not. All of these options incur variable cost and benefits.
Hearing aids specifically designed for patients with high-frequency hearing loss are available that do not have the occlusive effect of conventional hearing aids. A tiny piece fits behind the ear and a thin transparent plastic tube sits slightly in the ear canal. These aids tend to produce less static than conventional aids.
Advances in electronic technology, such as digital hearing aids, are moving faster than the research to determine the most effective signal-processing method. Improvements in hearing aids now include features such as noise cancellation, wind noise reduction, wireless capabilities, and the ability to assess the environment and automatically determine the best hearing condition for the patient. These advances should provide a better quality of life for the individual with reduced hearing.
Fitting — Hearing aids should be fit by a licensed and qualified professional to avoid problems with feedback and reliability associated with poor-quality hearing aids. Hearing aids must be properly fit, and digital hearing aids must be properly programmed. Not all dispensers of hearing aids take the time required to do this properly; it may make sense to suggest to patients that they see a licensed audiologist for this purpose .
A trial period is typically offered, during which the patient uses the hearing aid for 30 days. The cost of the aid is refundable except for a modest fitting fee.
Barriers to use — Less than one-half of the older adult population with significant hearing impairment, who would benefit from hearing amplification, actually wears a hearing aid [9-11]. In a report using data from the US National Health and Nutrition Examination Survey (NHANES), only one in seven individuals 50 years and older with hearing loss uses a hearing aid . In another study, only 20 percent of adults between the ages of 55 and 74 who would benefit from using a hearing aid actually used one . A systematic review estimated that anywhere from 5 to 40 percent of patients with a hearing aid do not use them .
Reasons cited for these low numbers include lack of appreciation of the consequences of hearing loss, discomfort, absence of insurance reimbursement, and fear of social stigmatization. In some older individuals, social withdrawal, lack of motivation, or inability to adapt to using new technology may also play a role. This occurs despite the fact that part of the social withdrawal may be due to frustration with the inability to hear. An observational study found that scores on a depression scale improved at six months, compared with baseline, in older adults who were hearing aid recipients .
Most of these individuals without severe hearing impairment would benefit from a hearing aid trial . A 2014 review of 32 studies evaluating interventions to improve hearing aid use did not find any interventions that consistently improved use .
BONE CONDUCTION HEARING DEVICES — Certain patients who are unable to benefit from standard air conduction hearing devices (a conventional hearing aid) may benefit from a device that transmits sound directly through the skull to the functioning cochleae (or cochlea, in the case of single-sided deafness).
Potential indications for the use of a bone conduction hearing system include:
●Congenital atresia of the ear canal, such that it does not exist or cannot accommodate a standard hearing aid
●Chronic infection of the middle or outer ear that is exacerbated by the use of a standard hearing aid
●Allergic reactions to standard hearing aids
●Single-sided deafness as may occur following removal of an acoustic neuroma, trauma, or due to a viral or vascular insult
Bone conduction hearing aids can be held against the skull with a steel-spring headband; however, this is typically painful, cumbersome, produces skull deformities, and does not achieve good-quality hearing.
By contrast, an implantable bone conduction hearing aid has advantages in terms of better tolerability and improved sound quality. The most widely used implantable system is a bone-anchored prosthetic device known as a bone-anchored hearing aid (BAHA). In the BAHA system, a small titanium implant is inserted into the skull where it osteointegrates. An abutment is attached to the implant, with a small portion sticking out through the skin; this acts as a snap attachment point for a removable bone conduction hearing aid. Alternatively, a magnetic abutment can be used, with the external sound processor connecting to this abutment magnetically such that there is nothing protruding from the skin. In both cases, the external processor can be detached when not in use. The sound quality of a BAHA is far superior to that of traditional bone conduction hearing aids, and other than the discomfort associated with initial placement, there is no pain with regular use of the device.
A case series report in patients with single-sided deafness demonstrated improved speech discrimination with a bone-anchored hearing aid [16,17].
COCHLEAR IMPLANTS — Cochlear implants are surgically implanted prosthetic devices that use electrical stimulation to provide hearing (figure 1). The criteria for selecting cochlear implantation include moderate to severe sensorineural hearing loss and a patient who still struggles to hear and understand despite appropriately fit hearing aids. Although cochlear implants are primarily used for those with bilateral hearing loss, they may also be used in patients with severe unilateral sensorineural hearing loss, with or without tinnitus .
Cochlear implant candidates do not need to be totally deaf. Indeed, most patients have some hearing and the sentence recognition scores can be up to 60 percent in best aided conditions.
The benefits and risks of cochlear implants in adults are generally similar to those in children. A meta-analysis of 42 studies concluded that cochlear implants in adults provided significant benefit and increase in quality of life . Studies have also suggested that cochlear implants are safe and have benefits for older adult patients (≥70 years) [20,21]. (See "Hearing loss in children: Treatment", section on 'Cochlear implants'.)
Differences between cochlear implants in children and adults include:
●The best candidates for cochlear implants are postlingual (had speech and language skills before losing their hearing), and most adult candidates for a cochlear implant fall into this category.
●Adults typically perceive more of a mechanical sound after implantation; the sound typically becomes more natural after four to eight weeks.
●Adults with bilateral hearing loss benefit from bilateral implants, which improve speech perception, allow better hearing in conditions with significant background noise, enhance sound localization, and allow the patient to hear sound coming from either side without having to turn one's head [22,23]. In a randomized trial including 38 patients, those who received bilateral implants performed better when noise came from different directions and were better able to localize sound compared with those receiving unilateral implants .
DIRECT-TO-CONSUMER HEARING AIDS — The 2017 Over-the-Counter Hearing Aid Act directed the US Food and Drug Administration (FDA) to establish a set of criteria and regulations for over-the-counter hearing aids . In 2022, the FDA established the regulatory criteria, and over-the counter hearing aids will be available for purchase by consumers in the United States beginning October 2022 . These devices must still meet the same high standards as other medical devices including safety, labeling, and manufacturing protection. They are intended for use in those with perceived mild to moderate hearing loss. Some, but not all available devices require an audiogram (in-person or online). Many are self-fit, self-tune hearing aids that do not require a health care professional, while other devices utilize an online audiologist to assist with adjustment. Those that are true self-fit with no health care professional requirement typically cost less than USD $1000 per pair, while those that utilize a health care professional for adjustments cost approximately the same as the traditional hearing aids sold by audiologists.
OTHER AMPLIFICATION DEVICES — Apart from hearing aids, other devices are available to amplify sounds for patients with hearing loss. These include amplified telephones and portable amplification systems. These latter use infrared technology to send sound to a headset from an external source, such as the audio output from a television set or the sound system in a public theater or church .
Personal sound amplification products (PSAPs) are relatively low-cost devices that amplify sound and which can be purchased directly by the consumer. These products have improved over time but do not have all the capabilities of hearing aids or easy programing for more complex hearing loss patterns. However, several studies have shown that some of these devices perform comparably with traditional hearing aids in certain settings [27,28]. The author would argue that low-cost PSAPs would work better if a patient worked with an audiologist to ensure the device was properly programmed for that patient.
EMERGING TECHNOLOGY — Progress in wireless and digital chip technology, combined with advances in cognitive and medical science, promise the potential for greater individualization of devices to improve hearing . Improvements in directional microphone technology allow isolation of desired sounds .
Studies are ongoing of hearing aids that are surgically implanted in the middle ear. One device, the Esteem, is approved by the FDA for severe hearing loss . However, it is only offered in a limited number of centers, is not covered by insurance, and is expensive. Other devices are not yet available to the general public. Long-term efficacy of these devices is unknown , and the reoperation rate is over 20 percent .
Similar implantable devices are available which use sound processors to enhance ossicular motion; such devices, however, require an external hearing aid device to be worn. Long-term efficacy is unknown, and out-of-pocket costs are generally high as these devices are not covered by insurance.
A new type of hearing aid is placed on the eardrum by a clinician and replaced every three to four months. It is available only in select areas, and it is costly; its effectiveness is still to be determined.
Another new type of hearing aid uses a behind-the-ear hearing aid and an ear canal mold that convert sound to light rays. A lens sits on the ear drum and is driven by these light rays. This technology decreases sound distortion, but not all patients have an ear canal or ear drum that is appropriate for this hearing aid. Cerumen (ear wax) can interfere with the use of this device, and these hearing aids are expensive.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Hearing loss and hearing disorders in adults".)
SUMMARY AND RECOMMENDATIONS
●Identifying appropriate candidates for hearing aids – The first step in providing hearing amplification is to determine whether a patient will benefit from a hearing aid. This is based upon (see 'Identifying appropriate candidates' above):
•Audiometric word discrimination
•Motivation level of the patient
•A discussion with patient about a hearing aid's maximum benefits
●Candidates for bone conduction hearing devices – Patients who are unable to benefit from a standard air conduction device (a conventional hearing aid) may benefit from a bone conduction hearing device that transmits sound directly through the skull. Potential indications for such an implantable system include (see 'Bone conduction hearing devices' above):
•Congenital atresia of the ear canal
•Chronic infection of the middle or outer ear
•Allergic reactions to standard hearing aids
●Role of cochlear implants – Cochlear implants are surgically implanted prosthetic devices that use electrical stimulation to provide hearing. The criteria for selecting cochlear implantation include moderate to severe sensorineural hearing loss and little or no benefit from conventional hearing aid use. For patients with bilateral hearing loss, bilateral implants may lead to significant improvement in hearing, vocalization, quality of life, mood, and cognition. (See 'Cochlear implants' above.)
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