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INTRODUCTION — Presbycusis, or age-related hearing loss, is a common cause of hearing loss in adults worldwide . Presbycusis is a complex and multifactorial disorder, characterized by symmetrical progressive loss of hearing over many years. It usually affects the high frequencies of hearing, although its presentation and clinical course can be variable. Presbycusis has a tremendous impact on the quality of life of millions of older individuals and is increasingly prevalent as the population ages .
This topic will focus on the pathophysiology, clinical presentation, evaluation, and management of presbycusis. The etiology and evaluation of other specific causes for hearing loss, as well as hearing amplification, are discussed separately. (See "Etiology of hearing loss in adults" and "Evaluation of hearing loss in adults" and "Hearing amplification in adults".)
EPIDEMIOLOGY — The prevalence of hearing loss increases with age, with up to 80 percent of functionally-significant hearing loss occurring in older adults . In one population cohort in the United States, the prevalence of hearing loss (defined by audiometry) increased steadily with age :
Presbycusis affects more than half of all adults by age 75 years [5-8]. Presbycusis is more common in men than women, but this finding may be related to higher levels of noise exposure seen in men.
The World Health Organization (WHO) estimates that in 2025, there will be 1.2 billion people over 60 years of age worldwide, with more than 500 million individuals who will suffer significant impairment from presbycusis .
Risk factors — Multiple factors can influence the onset and severity of presbycusis . These factors include low socioeconomic status, noise exposure, ototoxins (eg, aminoglycosides, chemotherapeutic agents, heavy metals), infections, smoking, hypertension, diabetes, vascular disease, immunologic disorders, and hormonal factors (eg, estrogen) [11-17]. A genetic component also predisposes individuals to age-related hearing loss [18,19].
ANATOMY — The normal ear can be divided into three anatomic areas: the external ear, middle ear, and inner ear (figure 1). Disorders of any of these areas can contribute to hearing loss. The external ear includes the pinna and the external auditory canal, which directs sounds to the middle ear. The middle ear includes the tympanic membrane, tympanic cavity, ossicles, and the eustachian tube. The middle ear functions to pass sound vibrations from the external ear to the inner ear. The inner ear is a geometrically complex, fluid-filled organ that resides within the dense otic capsule in the temporal bone. The inner ear is the organ of hearing (cochlea) and balance (vestibular system), both of which translate motion of fluid around hair cells (from either sound or head acceleration) into neural signals (figure 2). The stria vascularis, a system of small blood vessels, produces the fluid (or endolymph) for the scala media, one of three fluid-filled compartments of the cochlea. The neural signals produced by the hair cells and surrounding fluid enter the spiral ganglion and are subsequently carried to the brain by the vestibulocochlear (eighth) cranial nerve. (See "Etiology of hearing loss in adults", section on 'Anatomy and physiology'.)
PATHOPHYSIOLOGY — Hearing loss can be subdivided into two broad categories: conductive and sensorineural. Conductive hearing loss is characterized by the inability to mechanically transmit sound vibrations from the environment to the inner ear. Conductive loss is due to disorders of the external and middle ears. Sensorineural hearing loss is characterized by the inability to effectively transduce sound information into usable neural signals. The majority of sensorineural loss is the result of disorders of the inner ear itself and is not directly related to dysfunction of the vestibulocochlear nerve. Thus, the term “nerve deafness” is often a misnomer given that the primary dysfunction occurs in the inner ear, not the nerve. Presbycusis is a true sensorineural loss, in which both cochlear hair cells and, to a lesser extent, the spiral ganglion cells in the vestibulocochlear nerve can be affected [2,20,21]. (See "Evaluation of hearing loss in adults" and "Evaluation of hearing loss in adults", section on 'Classification of hearing loss'.)
Temporal bone histology provides some insight to the underlying pathophysiology of presbycusis. In the histopathology classification system, presbycusis is subdivided based on the associated audiometric pattern of loss, with abnormalities of inner ear vasculature, hair cells, and membranes all contributing to audiometric findings [20,22]. The three main types of presbycusis proposed by this system include:
Despite its continued usage, the validity of this histopathologic classification system has been questioned, since it appears that no single histopathologic finding can reliably account for the clinical variability seen in presbycusis [23-27].
In studies of temporal bones from patients with typical presbycusis, the degree of hearing loss was associated with disorders of a number of vital cochlear anatomic structures . These include degeneration of the stria vascularis, spiral ganglion cells, and hair cells. Consistent with findings seen in other causes of sensory hearing loss, the outer hair cells were the predominant structures affected. Thus, presbycusis appears to be most related to loss of inner ear sensory structures, although the underlying inciting events for this remain unclear.
CLINICAL PRESENTATION — The hallmark of presbycusis is the progressive, symmetric loss of high-frequency hearing over many years . Hearing loss can also be accompanied by tinnitus, vertigo, and disequilibrium leading to falls. Presbycusis can greatly impact quality of life, causing low self-esteem, isolation, and depression [28,29]. Presbycusis may also be associated with dementia, which is discussed separately. (See "Risk factors for dementia", section on 'Others'.)
Hearing loss — The progression of hearing loss is variable, but the typical course is a slow, persistent decline in hearing with age (figure 3). The hearing loss begins in the sixth decade and is typically symmetrical, beginning in the high-frequency range (figure 3).
The frequencies most affected by presbycusis are those above 2 KHz. Over time, the high frequencies will continue to drop, and the mid and low frequencies (0.5 to 2 KHz), associated with human speech, also become progressively involved. The low and mid frequencies of human speech carry the majority of energy of the sound wave. This includes most of the vowel information of words (figure 4). It is the high frequencies, however, that carry the consonant sounds, and therefore the majority of speech information. These consonant sounds tend to be not only high pitched, but also soft, which makes them particularly difficult for patients with presbycusis to hear. As a result of their hearing loss pattern, patients with high-frequency hearing loss will often report being able to hear when someone is speaking (from the louder, low-frequency vowels), but not being able to understand what is being said (due to the loss of consonant information).
Hearing deficits are exacerbated in the presence of competing background noise. The missing high frequencies are essential to allow the inner ear to focus on sounds of particular interest and pick those sounds out from competing ambient noise. Patients with presbycusis will often perform quite well in one-on-one communication in a quiet room, but the ability to hear will decline when there is even a small amount of competing noise. This experience is often referred to as the “cocktail party effect,” which emphasizes the difficulty that patients experience with communication in social settings. Patients also will often complain that they have more difficulty hearing women than men, which is the result of the inherently higher pitch of women’s voices.
Many patients will wait for several years before seeking help for presbycusis and are often brought to medical attention at the insistence of family members. This is in part due to the insidious onset of the disorder, as well as the negative stigma associated with hearing aid use. Older individuals may accept some degree of hearing loss as inevitable, and do not consider it a treatable disorder. Left unrecognized, hearing loss in older adults can lead to progressive social withdrawal, depression, isolation, and significant familial stress . Hearing loss also may have a significant deleterious effect on the spouses of affected individuals . The impact of hearing loss can be further compounded by the higher incidence of hearing loss in individuals with other coexisting functional limitations .
A common finding in patients with inner ear hearing loss is a paradoxical hypersensitivity to loud sounds. Patients will often complain that sounds become too loud at levels that would easily be tolerated by persons with normal hearing. This is the result of “recruitment,” a disordered processing of sound in the inner ear . The simultaneous elevation of the threshold needed to hear quiet sounds, and the reduction of tolerable loud sounds, results in a narrowing of the individual’s dynamic range. This can complicate fitting hearing aids for affected individuals, where careful upper output limits must be set to maintain comfort levels. Recruitment explains why shouting at patients with presbycusis is often quite counterproductive, since it is primarily the low vowel frequencies that are amplified by shouting, which carry little of the missing speech information and can be quite uncomfortable to the listener.
Tinnitus — Tinnitus can be an important problem as hearing loss progresses [33,34]. The tinnitus is most commonly a steady ringing, rushing, or “static” sound, but may be described as a broad range of sensations, including musical tones, bells, or “chirping.” The sound is usually described as affecting both ears or presents diffusely “in the head.” Tinnitus occurring in only one ear should prompt the clinician to initiate further evaluation for other etiologies. In addition, the presence of a pulse-synchronous rushing sound may require additional imaging to exclude vascular disorders. (See "Etiology and diagnosis of tinnitus" and 'Diagnostic imaging' below.)
Dizziness — Associated loss of vestibular end-organ function, termed “presbyastasis,” can contribute to vertigo, disequilibrium, and falls . The consequences of the loss of peripheral vestibular function is exacerbated by the presence of coexisting disorders, such as peripheral neuropathy, arthritis, peripheral vascular disease, and decreased visual acuity. Such conditions can limit the ability of an older individual to compensate for peripheral vestibular dysfunction. With the early recognition of presbycusis and dizziness, patients and caregivers can initiate measures to increase function and mobility while reducing the risk of falls and their potentially devastating complications. (See "Approach to the patient with dizziness" and "Prevention of falls and complications of falls in community-dwelling older persons".)
EVALUATION — The diagnosis of presbycusis should be suspected based upon a history of slowly progressive, symmetrical hearing loss in the older patient. The physical examination may be helpful in determining the type of hearing loss (conductive versus sensorineural), possible contributing factors for hearing loss (eg, cerumen), or other causes of hearing impairment (eg, tumors such as acoustic neuroma). Patients with hearing loss require formal audiogram testing to confirm the diagnosis, determine severity, and to direct management. Other testing such as blood testing, specialized audiologic assessment, and diagnostic imaging should be performed only if indicated by specific symptoms or signs of other disease. This is discussed in detail elsewhere. (See "Evaluation of hearing loss in adults".)
There is no consensus regarding population screening for hearing loss. An evidence-based review for the United States Preventive Services Task Force (USPSTF) determined that additional research is needed on the effectiveness of screening for hearing loss, with a particular focus on health outcomes . The USPSTF is preparing a recommendation statement on screening for hearing loss in older adults, which should be available in 2011 . The American Speech-Language-Hearing Association has advised that individuals over 50 years of age should have complete audiometric testing every three years . However, concerns have been raised about the resource implications without proven benefit . Taking a careful hearing history from all patients over 50 years of age, and further testing those who report hearing difficulties will identify most individuals with significant hearing deficits from presbycusis.
Clinicians should practice methods to facilitate communication with hearing-impaired patients. Facing the patients will allow them to use lip-reading cues. Speaking slowly, and not changing topics abruptly, will allow them to continue to put new information into context. Speaking clearly, without shouting or over-articulating (and using a lower-pitched voice) can aid comprehension. Patients with hearing loss may nod and appear to follow a conversation even when they are not. By engaging them actively in the conversation the clinician can ensure that they are indeed receiving information.
History — Multiple potential etiologies of hearing loss should be considered prior to making the diagnosis of presbycusis (table 1). A careful history of associated factors, such as family history, ototoxic medications, trauma, and concurrent otologic symptoms can help elucidate potential etiologies. The diagnosis of presbycusis should be questioned if the hearing loss is asymmetric, which should lead to evaluation for other conditions, such as otitis media, tumors, trauma, or asymmetric noise exposure (as often occurs from firearms exposure or the long term use of power tools on one side). (See "Etiology of hearing loss in adults".)
In addition to asking about hearing loss, a questionnaire can be helpful in eliciting a more detailed hearing history. The Hearing Handicap Inventory for the Elderly-Screening (HHIE-S) is a simple questionnaire that can help identify older adult patients with significant hearing impairment (table 2) [31,40,41].
Presbycusis develops over many years, and the rate of hearing loss progression can help to establish a diagnosis. It is often difficult for a patient or family member to give an accurate history of the onset and progression of hearing loss. However, the history of sudden decrease in hearing (noticed over days or weeks rather than years) should raise suspicion for other etiologies. (See "Sudden sensorineural hearing loss".)
Physical examination — The physical examination generally includes otoscopy, in addition to the whispered ear test and tuning forks for the assessment of hearing loss. The full ear examination is discussed in detail elsewhere. (See "Evaluation of hearing loss in adults", section on 'Examination'.)
The physical examination of the outer ears should be normal in presbycusis. The otoscopic examination may be useful for assessing other potential causes of hearing loss such as cerumen impaction, infection, tympanic membrane perforation, or tumors (eg, exostosis, osteoma, polyps).
Although audiometry is the most widely accepted diagnostic test for hearing loss, the whispered voice test is a simple test that can be performed in the primary care clinician’s office without equipment . To perform a whispered voice test, stand at arm's length behind the patient (to prevent lip reading) and mask hearing in one ear by occluding the ear canal and rubbing the tragus with a circular motion. Whisper a short sequence of letters and numbers and ask the patient to repeat them. Test the other ear in a similar manner. A tone-emitting otoscope is another reliable method for detecting hearing loss. (See "Evaluation of hearing loss in adults", section on 'Office hearing evaluation'.)
The Weber and Rinne tests, using tuning forks, can help distinguish conductive or sensorineural hearing loss, and identify an asymmetrical hearing loss (figure 5 and table 3). (See "Evaluation of hearing loss in adults", section on 'Weber and Rinne tests'.)
Audiogram — Hearing is measured by standardized audiometric testing which assesses both the ability to hear tones and understand words. Pure tone thresholds are determined by presenting the subject with a variety of tones of frequencies varying between 250 Hz and 8 KHz. In a patient with presbycusis, an audiogram will show downward-sloping pure tone thresholds with relative preservation of word recognition scores (figure 3). The thresholds needed to just perceive these tones are recorded, with normal values falling below 25 decibels (dB). Human speech is mainly comprised of sounds falling between 500 Hz and 4 kHz, with average conversational levels falling at about 50 dB of loudness. Vowels tend to be lower and louder, while the consonants, which carry the majority of meaning of words, fall in the higher and softer range (figure 4).
In addition to measuring pure tone thresholds, complete audiometric analysis includes a measure of the ability to understand a standardized list of words presented at a comfortable listening level. This is termed the “word recognition score,” with normal hearing individuals being able to correctly identify 90 percent or more of words presented. This is a measure of the subject’s ability to process sound, and often decreases disproportionately in cases of neural or central dysfunction. Good word recognition scores predict favorable response to amplification, since they indicate that the patient can understand words if they are amplified to comfortable levels. Further aspects of the audiologic assessment are discussed elsewhere. (See "Evaluation of hearing loss in adults", section on 'Formal audiologic assessment'.)
Older patients with suspected hearing loss require formal audiogram testing to confirm the diagnosis, determine severity, and to direct management. Monitoring the patient with a follow-up audiogram is also advisable . These may be scheduled yearly or more frequently if deterioration of hearing is observed or new otologic symptoms develop.
Diagnostic imaging — Imaging studies, including MRI and CT, are not indicated for the diagnosis of presbycusis. An MRI may be indicated to exclude neural or central pathology in cases where there is significant asymmetry of hearing loss, or other indications of possible tumor, such as vestibular schwannoma or other skull base lesions . This should be particularly considered if there is associated unilateral or pulsatile tinnitus, vertigo, or other cranial nerve deficits.
MANAGEMENT — Despite the high prevalence and impact of presbycusis, a directed treatment to prevent or reverse its effects is not available. However, multiple options can compensate for hearing loss and improve daily function and well-being . Simple recognition of the problem can be a major positive step, as hearing loss in older adults is often mistaken for cognitive impairment. The identification of hearing loss can be reassuring for many patients . If the diagnosis of presbycusis is made, one can attempt to identify and avoid additional factors that can contribute to hearing loss, such as ongoing noise exposure or the use of potentially ototoxic medications.
Most patients with significant age-related hearing loss will benefit from use of a hearing aid. Cochlear implantation is utilized for hearing loss refractory to hearing aids. Assistive listening devices and auditory rehabilitation may also be helpful in the management of presbycusis. Interventions to improve hearing are particularly important in older patients with dementia because hearing impairment further exacerbates cognitive impairment and functional decline in these individuals.
Hearing aids — Hearing aids can improve hearing function for most cases of presbycusis . The progression of hearing loss rarely becomes so severe that hearing aids are not effective in restoring the ability to communicate. The use of appropriately-fit hearing aids can ameliorate the withdrawal, depression, and emotional impact that are commonly associated with presbycusis  and can lead to improvement in quality of life . Specific issues related to hearing amplification are discussed separately, including identification of appropriate candidates, choosing the type of hearing aid, and fitting. (See "Hearing amplification in adults".)
Many patients have had negative experiences with hearing aids, or have heard other patients’ negative reactions to hearing aids. At times, hearing amplification is not tolerated either because patients produce too much cerumen, which plugs the device, the meatus is too small, or the device has increased static or noise. The aid may also cause discomfort, and it is a cosmetic concern to many patients. Finally, it may not allow the patient to understand speech any better, but rather only allows the patient to hear noise at a louder level . Unfavorable experiences can be avoided through careful testing, counseling, device selection, and fitting by an experienced audiologist. Most dispensing audiologists will offer trial periods to minimize the financial risk to the patient. Technological advancements in hearing aids, such as direction-specific microphones, improved speech processing strategies, and additional customization options, may have improved performance significantly from when patients last tried amplification .
There are no strict criteria when hearing amplification should be recommended. When the high-frequency thresholds are greater than 40 dB on the audiogram, a trial of hearing amplification is generally indicated. Lesser degrees of hearing loss may warrant amplification when employment, educational needs, or social needs require finer hearing.
Well-fit hearing aids will also help with the tinnitus experienced by many patients with presbycusis . There is a balance between sounds heard externally and those generated internally. The restoration of missing frequencies will often noticeably reduce the perception of bothersome tinnitus. (See "Treatment of tinnitus".)
Despite the fact that hearing aids offer potential help, only a small percentage of patients with presbycusis actually receive effective treatment with amplification . Studies in Western countries suggest that only 10 to 20 percent of adults with significant hearing loss actually have a hearing aid [2,31,50]. In addition, as many as 25 to 40 percent of adults who have hearing aids underutilize or abandon hearing aid use. This emphasizes the need for well-trained hearing professionals to provide counseling, fitting, assistive listening devices, and/or rehabilitation services to maximize the chance of benefit. (See 'Assistive listening devices' below and 'Auditory rehabilitation' below.)
Cochlear implantation — For patients so severely affected by presbycusis that conventional amplification strategies are no longer effective, cochlear implantation offers hope to restore hearing. Cochlear implantation involves the placement of an electrode array within the inner ear to bypass the damaged cochlea, and stimulate the remaining cochlear neurons directly with electrical stimulation (figure 6). This procedure can be performed safely, even in octogenarians .
Cochlear implant outcomes in presbycusis patients may be limited by the age-related reduction in ability to process sound information, as well as age-related cognitive deficits. Hearing impairment can also result from a loss of cochlear nerve fibers that the implant stimulates [13,52]. Despite these considerations, the great majority of patients undergoing cochlear implantation for presbycusis can be expected to achieve significant functional improvement, similar to that seen in younger patients [49,53-57]. Cochlear implants are indicated for people with bilateral severe hearing loss that is not significantly improved with hearing aids . (See "Hearing amplification in adults", section on 'Cochlear implants'.)
Assistive listening devices — A variety of assistive listening devices can reduce the impact of presbycusis on daily life . These may be linked with hearing aids, such as telecoils for telephone use or frequency-modulation systems that transmit sound information directly to an individual’s hearing aid. Assistive listening devices may also be independent of hearing aids, such as tactile or visual alerts that can compensate for lack of auditory input (eg, flashing lights for a doorbell).
Patient satisfaction with assistive listening devices is generally good, although there is some variability depending on the specific listening environment in which they are applied . High-fidelity frequency-modulation systems that transmit sound directly to a user’s ears are a popular option, and can be of particular benefit in theaters and lecture halls with otherwise adverse acoustics [60,61]. They can be helpful for listening to television, and can reduce the stress of trying to find the right volume for a number of television viewers. The use of captioning for television viewing can also significantly improve comprehension for patients with presbycusis . Assistive listening devices can be used in several settings, including at home, at work, and in the classroom [62,63].
Auditory rehabilitation — Auditory or aural rehabilitation is defined as sensory management, instruction, perceptual training, and counseling for hearing impairment . Auditory rehabilitation includes interventions such as active listening training, speech reading, and communication enhancement. Specific examples include education on reading facial expressions or lip contours of speakers, interpreting contextual cues such as posture to overcome fast speech, and maximizing environmental factors such as ensuring adequate lighting or phasing out competing sound sources . These treatments are usually administered through one-on-one training, as well as in the group setting. Auditory rehabilitation, when available, is usually practiced in combination with hearing devices.
Patients can use specific strategies to improve their communication abilities. Selecting restaurants and venues with favorable acoustics can significantly improve the experience, as can positioning companions on the side of a more favorable ear. One of the most important strategies is for those with hearing loss to actively inform companions about hearing loss. In this way their companions can make a habit of using beneficial communication techniques (eg, speaking slowly and clearly while facing the individual with hearing loss).
A systematic review of auditory rehabilitation found that there is little evidence that rehabilitation improves communication due to hearing loss . In addition, it is not known which methods of rehabilitation are most likely to be helpful in which populations, alone or in combination with hearing devices. Despite lack of efficacy, auditory rehabilitation is still routinely performed, and newer rehabilitation methods are being developed such as speech tracking and analytic auditory training in computerized forms that may offer benefit .
Future interventions — Future treatments for hearing loss may include genetic, cellular, or pharmacotherapy to induce the regeneration of hair cells to repopulate the damaged regions of the cochlea . The identification of endogenous stem cells within the inner ear offers hope for stem cell therapy [68-70]. The ability to unlock the regenerative potential of such cells could help to address the fundamental deficits in presbycusis. Further understanding is needed of the underlying causes of age-related hearing loss so that more targeted interventions can be developed.
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