Continuing Education Activity

Presbycusis refers to bilateral age-related hearing loss. In literal terms, presbycusis means 'old hearing' or 'elder hearing. It is the most common cause of hearing loss worldwide and is estimated to affect approximately two-thirds of Americans aged 70 or older. The hallmark of presbycusis is the impaired ability to understand high-frequency components of speech (voiceless consonants, such as p, k, f, s, and ch). This activity reviews the evaluation and management of presbycusis and highlights the role of the interprofessional team in improving care for patients with this condition.

Objectives:

• Describe the classic patient's history associated with presbycusis.
• Outline the appropriate evaluation of presbycusis.
• Review the management options available for presbycusis.
• Summarize the importance of collaboration and communication among the interprofessional team to enhance the delivery of care for patients affected by presbycusis.

Introduction

Presbycusis refers to bilateral age-related hearing loss. In literal terms, presbycusis means "old hearing" or "elder hearing."[1] It becomes noticeable around age 60 and progresses slowly; however, there is evidence that certain stressors can speed the rate of deterioration. The diagnosis can be confirmed with audiometry.[2] The hallmark of presbycusis is the impaired ability to understand high-frequency components of speech (voiceless consonants, such as p, k, f, s, and ch).[3] There is no cure; however, hearing aids that amplify sounds can be used to mitigate symptoms. Anatomically, presbycusis involves multiple components of the auditory system. It is primarily due to age-related changes in hair cells, the stria vascularis, and afferent spiral ganglion neurons.[4]

During the normal hearing, sound, in the form of air vibration, is captured by the funnel-shaped external ear and is directed to the tympanic membrane. This causes the tympanic membrane to vibrate at a specific frequency and amplitude. This movement is amplified by three small bones in the middle ear: the malleus, incus, and stapes. From there, the signal proceeds as vibrations that are transmitted through the fluid within the inner ear to the cochlea. In the cochlea, receptors known as hair cells transform the information encoded in the vibrations into a neurologic signal which travels to the auditory cortex via the cochlear nerve.[5]

Etiology

Presbycusis is multifactorial in origin. In addition to age-related degeneration leading to physiologic and anatomic changes, other contributing factors include genetic factors, hormones, exposure to loud noises or ototoxic agents, history of ear infection, and the presence of certain systemic diseases.[6][7]

Age-Related Factors

Presbycusis can be broken down further with regards to which structures and functions are primarily affected. Some argue that there is little clinical utility in subdividing presbycusis as there is no significant change in approach or treatment, and oftentimes mixed pathology is present.[6][8][9] Presently, there are thought to be six categories of presbycusis: sensory, neural, strial, mechanical, mixed, and indeterminate.[4][10]

• Sensory presbycusis: loss of receptor hair cells at the basal aspect of the cochlea resulting in characteristic high-frequency hearing loss.[6]
• Neural presbycusis: loss of cochlear nerve fibers as well as the loss of spiral ganglion neurons.
• Strial presbycusis: degeneration of stria vascularis cells. These cells are essential for maintaining the appropriate ion composition of endolymph to generate the endocochlear potential for signal transduction.[11] Sometimes referred to as metabolic presbycusis.
• Mechanical presbycusis (cochlear conductive): due to physical changes of the cochlear duct. This is accompanied by a specific audiogram pattern.[4]
• Mixed presbycusis: characterized by pathologic changes in more than one of the above structures.
• Indeterminate presbycusis: cases in which changes to the above structures are not significant.[4]

Genetic Factors

Genetic factors, specifically, differences in mitochondrial DNA expression genes related to oxidative stress, have been found in patients with presbycusis when compared to controls.[12][13][14]

Ototoxic Factors

There are multiple medications associated with ototoxicity, including salicylates, loop diuretics, aminoglycoside, and certain chemotherapeutic agents.[15][16][17] Additionally, some work and environmental-related exposures to chemicals such as toluene, styrene, lead, carbon monoxide, mercury, and other toxins have been shown to cause ototoxicity.[18] Minimizing exposure to these agents can help to prevent age-related hearing loss.[19]

Noise Exposure Factors

Some long-term studies have shown that individuals who have sustained noise-induced cochlear damage in their youth go on to develop more severe presbycusis. Anatomically, noise exposure may lead to damage and subsequent loss of spiral ganglion neurons.[14][20]

Hormonal Factors

Glucocorticoids, sex hormones, and glutamate signaling are thought to play a role in presbycusis.[14] Prolonged corticosterone levels and loss of nuclear factor kappa B have been associated with increased spiral ganglion neuron loss.[21][22] The use of progestin and combination hormone replacement therapy in postmenopausal is associated with a more frequent incidence of hearing loss.[23]

Epidemiology

Presbycusis is the most common cause of hearing loss worldwide and is estimated to affect approximately two-thirds of Americans aged 70 or older.[24] It is difficult to determine the exact prevalence because the criteria used to define hearing loss differs among investigators. There have been multiple attempts to assess the frequency of hearing loss among large cohort populations, including participants from studies such as the national health and nutrition examination survey (NHANES), and the health aging and body composition (ABC) study.[25] According to data from NHANES, which represents a cross-section of non-institutionalized Americans, the prevalence of hearing loss approximately doubles with each subsequent decade from age 12 to age 79.[26] Among participants in the Health ABC study, hearing loss was most prevalent in white men, followed by white women, black men, and black women.[27]

Worldwide, there are similar increases in prevalence with age. Presbycusis affects more than half of older adults by age 75 and nearly all adults over age 90.[28] The World Health Organization estimates that by 2025, among those aged 60 and above, greater than 500 million will have significant age-related hearing loss.[29]

Pathophysiology

Presbycusis is thought to be multifactorial in origin, and some components are not fully understood. Both intrinsic factors, such as genetics, as well as external factors (noise exposure, smoking, medications, and certain co-morbidities), are involved.[3] It is primarily due to age-related changes in hair cells, the stria vascularis, and afferent spiral ganglion neurons.[4] Presbycusis is a type of sensorineural hearing loss with the involvement of the inner ear or neurologic pathways that form connections to the auditory cortex.[2]

History and Physical

Presbycusis is generally insidious in onset, and mild cases are difficult to detect. It is imperative that primary care providers screen for hearing loss, especially geriatricians and those caring for adults age 60 and beyond. Often, family members and friends are more aware of hearing loss than patients themselves. A common initial presentation is difficulty discriminating speech in specific situations, such as a room with significant background noise.[30] Some patients complain of tinnitus, or ringing in the ears, however, this is not specific to presbycusis.[3] Formal questionnaires exist, such as the hearing handicap inventory for the elderly-screening (HHIE-S). However, some investigators found this formal screening tool to be less sensitive and more time-consuming than the single question "Do you have a hearing problem now?"[31] Gathering a thorough history regarding the patient's ability to communicate, and ideally getting input from close contact can help to identify individuals who should be sent for further audiometry testing. Asking about recreational or occupational exposure to loud noises, the use of ototoxic medications, and family history of age-related hearing loss is also important. Referral to an otolaryngologist should be considered if the patient's hearing loss is acute, unilateral, or accompanied by neurologic symptoms, such as facial numbness or weakness, loss of balance, or dizziness.

The general physical exam is usually unremarkable in patients with presbycusis. It is common for older adults to have age-related benign opacification of the tympanic membrane and build-up of cerumen.[3] If a moderate amount of cerumen is present, this should be removed to rule out impaction or obstruction as a potential cause of hearing loss. Tuning forks may be used to discriminate between conductive and sensorineural hearing loss; however, their use is limited by patient cooperation and provider subjectivity. Determining whether the pattern of hearing loss is sensorineural or conductive is an important first step in the diagnosis. This can be done by performing both the Weber and the Rinne test using a tuning fork. These tests should not be used as screening or diagnostic tools, but simply for differentiating between conductive and sensorineural hearing loss.[32][33] Presbycusis is sensorineural in origin; therefore, the Rinne test should reveal that air conduction is heard longer than bone conduction in both ears. Weber's test should localize toward the ear with better hearing, signifying a contralateral sensorineural loss.[34] Weber's test may vary and may result in a falsely normal result if hearing loss is symmetric.

Evaluation

Routine physical exam maneuvers alone are not sufficient for diagnosing presbycusis. An in-office screening audiometry test administered by trained personnel should be considered by providers such as geriatricians who have a large population of older adults at high risk of presbycusis. There should be a low threshold for referral for definitive auditory testing in patients suspected of presbycusis. Imaging is usually not performed except in cases in which there is a discrepancy between presentation and auditory testing, or there are associated neurological changes.[3]

There are many variations of audiometry testing and central auditory testing that are beyond the scope of this review. In general, an audiometry exam tests the ability to hear sounds at varying intensity (loudness) and frequencies (tone). Commonly, pure tone testing (also known as an audiogram) is performed in patients with suspected age-related hearing loss. Pure tones are delivered through the use of headphones to one ear at a time. Patients are asked to respond if they hear a sound. The results are presented in the form of an audiogram, a graph with hearing level (in decibels) on the y-axis and frequency (in hertz) on the x-axis. In presbycusis, the highest frequency sounds are typically affected first, followed by lower and lower frequency sounds as the condition progresses.[30] Presbycusis is characterized by bilateral hearing loss above 2000 Hertz. On a standard audiogram, presbycusis appears as an overall down-sloping line that represents impaired hearing at higher frequency sounds.

Laboratory testing for diseases commonly associated with hearing loss, such as dyslipidemia, diabetes, and renal dysfunction, may be indicated but are not required for diagnosis.[3]

Treatment / Management

There is no cure for presbycusis. Hearing aids are the mainstay of treatment and have been shown to have a significantly positive effect on the quality of life and communication.[3] Hearing aids do have limitations. They do not repair normal hearing, but instead simply amplify sounds. Devices can be very expensive and often are not covered by the patient's insurance.[3][35] While smaller hearing aids are potentially more comfortable and discrete, decreased dexterity in geriatric patients may make these devices less convenient. Importantly, the management of hearing aids does not stop once the devices are fitted. Learning to use hearing aids and adjusting to both the physical discomfort and cognitive adjustment takes significant effort and practice. A collaborative, interdisciplinary approach involving the primary care provider and audiologist is recommended for continued auditory rehabilitation.[36] Patients often require encouragement as many find hearing aids uncomfortable, unattractive, and embarrassing.[3] Hearing aids are indicated at certain thresholds of hearing loss. Cochlear implants can be offered to patients with severe bilateral hearing loss that is not improved with hearing aids. Specific criteria exist for patients to be considered candidates, and often include a predetermined level of impairment in word identification.

As extrinsic factors are thought to have a role in the progression of presbycusis, wearing earplugs or earmuffs to attenuate sounds may be helpful if the patient needs to be exposed to loud noises. A diet low in saturated fat may help slow hearing loss.[37] Maintaining a healthy, active lifestyle is a logical form of risk reduction in light of the fact that hearing loss is associated with stroke, myocardial ischemia, hypertension, hyperlipidemia, and diabetes. Smoking should be discouraged, as cessation has been shown to delay age-related hearing loss.[38]

There is an abundance of ongoing research regarding the genetic and metabolic components of age-related hearing loss. Due to the potential role of oxidative damage, it was thought that antioxidants might slow the progression of hearing loss. While the administration of alpha-lipoic acid has been shown to prevent age-related hearing loss in rats, an antioxidant-enriched diet in humans did not delay the progression of hearing loss. Other agents, such as coenzyme Q-10 and ginkgo biloba, have been studied and lack sufficient evidence for use. Additionally, the use of these supplements is controversial as prolonged administration has been associated with an increase in overall mortality.[1] There are ongoing investigations into potential gene and hormone therapies for hearing loss.

Differential Diagnosis

Presbycusis is a diagnosis of exclusion.[39] If the pattern is consistent with sensorineural hearing loss, the patient should be referred for formal audiometry testing. The differential diagnosis for sensorineural hearing loss includes:[2][36]

• Noise exposure
• Infection
• Ménière disease
• Trauma
• Autoimmune disease
• Perilymph fistula
• Genetically-inherited hearing loss
• Otosclerosis
• Tumor
• Exposure to ototoxic agents
• Metabolic dysfunction

In addition to audiometry, further testing such as imaging or metabolic assessment can be considered if hearing loss does not follow classic presbycusis characteristics. Other conditions associated with presbycusis, such as diabetes, hypertension, renal impairment, and hyperlipidemia, should be evaluated.

If the pattern of hearing loss is conductive, then an alternative diagnosis to presbycusis should be considered. These include:[36]

• Cerumen impaction
• Foreign body
• Tumor obstruction
• Infection
• Perforation
• Otosclerosis
• Cholesteatoma

Presbycusis should be considered in older adults presenting with changes in mood and cognition as these may be due to underlying hearing impairment.[40]

Prognosis

Age-related changes in hearing are a natural consequence of getting older. Typically, presbycusis does not lead to deafness but ignored or untreated presbycusis can have serious consequences on mental, cognitive, and even physical health.[41][42][43] While there is no cure for presbycusis, hearing aids can help to improve symptoms and prevent or delay other consequences of impaired hearing.[3][30] To obtain the full benefit of hearing aids, it is important to encourage regular device use and participation in auditory rehabilitation so that the patient can adapt cognitively and behaviorally.[3] Hearing aids do not reverse age-related changes, and these changes will continue to occur even with treatment. If hearing aids are unsuccessful in helping to hear, surgical treatment options exist.

Complications

Impaired hearing contributes to cognitive dysfunction in older adults.[44] It has been shown that those with age-related hearing loss have an increased risk of developing dementia.[45][46][47] While there have been numerous studies that confirm the connection between the severity of hearing loss and cognitive impairment, the relationship is not completely understood. Some suggest that hearing impairment requires the brain to recruit more resources to make up for the deficits in auditory perception. Because there is a finite neurologic reserve, this recruitment takes away resources that could be used for other cognitive functions, such as memory.[48][49][50]

Hearing permeates through numerous aspects of daily living, including communication, safety, social interaction. Loss of hearing is believed to lead to increased social isolation and decreased autonomy in older adults.[41] Negative effects on mood, such as increased incidence of anxiety, depression, and lethargy, can be present.[42][51] Treatment of hearing impairment with such devices as hearing aids has been shown to have a significantly positive effect on the quality of life.[3][30]

Impaired high-frequency hearing can pose serious safety concerns, as it may be difficult for older adults to respond to warnings and signals, such as doorbells, ringing phones, smoke alarms, and turn signals. There is evidence for a relationship between hearing loss and postural control in older adults, which may be related to the perception of one's motion and position in space.[43][52] A deeper understanding of this connection may potentially impact the frequency of falls, a significant source of morbidity and mortality in the elderly.

Consultations

Management of patients suffering from presbycusis is teamwork, following specialties can help in the management of these patients to improve outcomes.

• Audiology: referral for formal audiometry testing, hearing aid fitting, and education
• Otolaryngology: if the hearing impairment is sudden in onset, asymmetric, or concern for different auditory pathology
• Neurology: for further investigation into other causes of hearing impairment, especially if there are cooccurring neurologic signs and symptoms (headache, loss of balance, vertigo, facial numbness/weakness, visual changes)
• Gerontology: if there are concerns for concurrent cognitive impairment or dementia
• Oncology: if there are concerns for ototoxicity related to specific cancer treatment regimens
• Psychiatry: for negative effects on mood, anxiety, and depression

Deterrence and Patient Education

A certain degree of presbycusis is inevitable with aging. It is important to educate patients, caretakers, and colleagues about the high prevalence of age-related hearing impairment and its many consequences. Successful interventions do exist. Early identification and treatment may help to slow progression and improve the quality of life.[3] It is important to screen all older patients (age 60 and beyond) for hearing impairment regularly. This can be as simple as asking, "Do you have trouble hearing?.

Because poor hearing is associated with cardiovascular risk factors, maintaining a healthy lifestyle, avoiding smoking, staying physically and cognitively active may help to delay the onset and slow the progression of hearing loss.[3][53] There are other well-established health benefits to these interventions; therefore, there suggesting to patients at risk of presbycusis may be appropriate, assuming there is simply an association that does not necessarily mean causation. Older adults should pay attention to the effect the environment has on their ability to understand sounds, especially in the presence of competing for auditory input and background noise.

Maintaining clean ears by safely removing cerumen and avoiding loud noises without ear protection may help to prevent other causes of hearing loss that can worsen the symptoms of presbycusis.

Enhancing Healthcare Team Outcomes

Presbycusis is very common and can have profound consequences on the quality of life. Due to wide variations in presentation, diagnosis may be delayed if patients are not specifically screened for hearing loss. Collaboration in care is an integral component of delivering efficient and effective health care. While the responsibility for screening rests mainly among primary care providers, most do not consistently assess hearing due to various barriers such as lack of time and reimbursement and the onus to address more pressing health issues.[35][54]

Prompt referral to an audiometrist or other care provider who can perform specific audiometric testing is warranted in patients who are suspected of having age-related hearing loss. Subspecialties in areas such as otolaryngology, neurology, and geriatrics also have an opportunity to screen for presbycusis. Additionally, nurses and other allied health professionals can help to screen older patients by asking about hearing problems during an encounter. Collaboration between audiologists and primary care providers has the potential to increase awareness of the prevalence of hearing loss and the importance of audiological rehabilitation.[55][56] [Level 1]

Interprofessional communication remains important after the diagnosis of presbycusis is made. Aural rehabilitation is essential in the management of age-related hearing loss. Hearing aids require significant time and effort from the patient and continued encouragement by the primary care provider and audiometry team.[57] As more information regarding the connection between cognitive impairment and hearing loss emerges, teamwork among geriatricians, neurologists, otolaryngologists, and audiologists will be even more important.