Overview
Hearing loss is a common and potentially disabling
problem in older individuals. While approximately one-quarter of older
individuals complain of hearing problems, at least one-third have significant
hearing impairment on audiological testing. Hearing loss may impair physical
and social function, and is associated with cognitive deficits, mood disturbances
and behavioral disorders. Ninety percent of hearing loss in the elderly
is due to sensorineural changes, and many cases are amenable to amplification.
Hearing aids improve the quality of life. On the basis of high prevalence
and proven effectiveness of intervention, there is fair evidence to include
screening for hearing impairment in the periodic health examination. Attempts
should be made to limit environmental noise-exposure to prevent noise-induced
damage to hearing.
Burden of Suffering
Age-related hearing loss (presbycusis) is a common
phenomenon, due to a variety of causes. Ninety percent of presbycusis is
due to sensorineural hearing loss, resulting from an interaction of age-related
changes, diseases and agents that damage hearing. Changes due to aging
include stiffening of the basilar membrane, hyperostosis, arteriosclerotic
and rheologic changes, together with degeneration of the organ of Corti,
loss of hair cells, spiral ganglion degeneration and impaired neural regulation
of endolymph. Other factors include infectious diseases of the middle and
inner ear, noise exposure, drugs (aminoglycoside antibiotics, salicylates,
quinidine, loop diuretics) and damage to the auditory nerve.
Hearing impairment refers to limitation of function as measured by raised hearing threshold, measured as decibels of hearing loss (dB HL) relative to the hearing of a normal population, at specific frequencies, usually 250, 500, 1,000, 2,000 and 4,000 Hz. Hearing disability refers to the limitation in performing everyday tasks such as understanding speech in the presence of background noise.
Presbycusis affects primarily frequencies above 1000 Hz. While the frequency of most speech is in the 500-4000 Hz range, certain consonants (e.g. S, Th, F) have higher frequencies. The elderly hearing impaired person may have normal low frequency hearing with loss in the mid and high frequencies. Thus, speech is audible but takes on a muffled character and is difficult to understand especially in the presence of background noise. As this type of hearing loss usually develops gradually over many years, the individual may be unaware of the impairment. Because of the ability to respond to low frequency sounds in speech, family and caregivers may attribute misunderstanding to confusion, forgetfulness or inattention. By preventing effective communication, hearing loss can affect physical, emotional, cognitive, behavioral and social functioning. Hearing loss is the most common chronic disability in North America.
At least 25% of individuals over the age of 65 report problems with hearing. Audiologically detectable hearing loss (HL) is present in more than one-third of all people over that age. In a large two-stage survey from the U.K. (postal questionnaire followed by clinical examination), 16% of adults (17-80 years) had a 25 dB HL or greater, 4% a 45 dB HL or greater and 1% a 65 dB HL or greater in both ears. Nine percent had a moderate (³45 dB HL) impairment in at least one ear.<1> While the overall prevalence of 45 + dB HL in adults aged 18-80 was 4%, it rose sharply with age. Between 61 and 70 years the prevalence was 7%, between 71 and 80 years it was 18%. Eighty percent of hearing loss occurs in people over age 60 years.<2> In the U.S. hearing loss is reported by 23% of persons age 65-74, 33% of those age 75-84, and 48% of persons age 85 and over.<3> In a study of women aged 60-85 residing in two small communities in rural Idaho, 45% had a ³25 dB HL in mid-range frequencies (1,000-4,000 Hz) and 18% had a ³40 dB HL in the better ear.<4> In the 18th examination of the Framingham study population, 41% of 1,662 men and women between the 60th and 90th year claim to have hearing problems, and 29% had a ³26 dB HL.<5> The prevalence of hearing loss is even greater in institutions; 45% of nursing home residents had a ³40 dB HL at 1,000, 2,000, and 4,000 Hz.<6> The Canadian Hearing Society estimates that 10% of the population are hard of hearing or deaf, (2,535,406 Canadians) and that 84% of people tested in nursing homes have hearing impairment.
Hearing impairment is associated with diminished function in the elderly. For example, in a case series of older individuals screened in primary care practice, a 10 dB increase in hearing loss was associated with a 2.8 point increase in physical Sickness Impact Profile scores.<7> Hearing impairment is associated with more rapid decline in cognitive function in people with Alzheimer’s diseases.<8> Even mild hearing loss is associated with memory failure.<9>
The rate for decline of hearing in presbycusis has been studied in a cohort of 1,475 persons over six years. The average threshold change ranged from 1-8 decibels at 250-6,000 Hz, and 10-15 decibels at 8,000 Hz.<10> In a paper drawing on data from longitudinal studies in Great Britain and Denmark, deterioration of hearing impairment appeared to be continuous and gradual for the majority (up to 97% on a two-year assessment) with a median of 5-6 decibels per decade.<11>
Maneuver
Detection maneuvers include screening questions,
physical tests and pure tone audiometry. In a population of 267 women between
the ages of 60 and 85 years from rural Idaho, the single question "Would
you say that you have any difficulty hearing?" was found to have a 90%
sensitivity for detecting a 40 dB HL at 1,000 and 2,000 kHz and an 83%
sensitivity for a 40 dB HL at 1,000 and 4,000 Hz in the better ear. Corresponding
specificities were 71% and 75%.<4> The whispered-voice test is administered
by whispering six test words at a set distance from the patients ear (6
inches to 2 feet) out of field of vision, and asking the patient to repeat
the words. Sensitivity for detecting hearing impairment is reported to
be between 80% and 100%, with specificities of 82-89%.<12> The tuning
fork test is performed by holding a vibrating fork one inch from the patient’s
ear and withdrawing it. Failure to hear a vibrating 512 Hz fork at a distance
of one foot has a reported sensitivity of 80% and a specificity of 65-82%.
Note that testing with a single low frequency is not suitable for screening
older people who characteristically lose higher frequencies in presbycusis.
The finger-rub test is carried out by rubbing thumb and forefinger together
and slowly withdrawing the hand until the patient no longer hears it. Failure
to hear this at a distance of 6-8 inches from the ear has a reported sensitivity
of 80% and a specificity of 49%. At 3 inches, the sensitivity is reported
to be 90%, and the specificity 85%.<12> Inter-observer variability data
is not available for the above tests.
The audioscope (manufactured by Welch-Allyn Inc.) is an instrument which serves as both an otoscope and simplified audiometer. It delivers pure tone frequencies at thresholds of either 25 or 40 decibels at 500, 1,000, 2,000 and 4,000 Hz. This instrument has been extensively evaluated, consistently performing with a high sensitivity (87-96%) and specificity (70-90%) in four separate studies.<13-16> The advantage of this instrument is that it allows for inspection of the external auditory meatus and tympanic membrane, while providing a standardized series of pure tones giving considerable accuracy and inter-observer agreement.
Sangster and colleagues offered hearing screening to all patients aged 65 years of age or older attending a family practice over a two-Many month period in London, Ontario.<17> Excluding those who had ever worn a hearing aid or who had signs of active ear pathology, screening included the use of the audioscope at a setting of 40 dB together with a ten-item screening version of the hearing handicap inventory for the elderly. (HHIE-S) The inventory contains five social-situational items and five emotional response items. Individuals failed the screening if there was a 40 dB HL or greater at 1,000 Hz and 2,000 Hz in one or both ears, or if they scored more than eight points on the HHIE-S. Of 115 individuals screened, 34 (30%) failed (9 failed audioscope, 14 failed HHIE-S and 11 failed both.) Twenty-five of these agreed to undergo complete audiological evaluation, and 9 declined this recommendation. Of the 25 individuals seen at the audiology clinic, 15 had severe hearing impairment. Eighteen were advised that they were candidates for a hearing aid and/or aural rehabilitation. An unexpected finding was that of 11 individuals with hearing aids, who also underwent complete audiological examination, 10 required major adjustment or replacement of their devices.<17> The sensitivity of the HHIE-10 alone is 65-75% and its specificity is 75-82%.<18,19>
Effectiveness of Prevention and
Treatment
Although prevention of hearing impairment may
not be possible, primary prevention of noise-induced hearing loss is achievable.
Noise control programs and hearing protection are believed to be efficacious<20>
based on multiple studies establishing an unequivocal relationship between
noise exposure and hearing loss. It is not considered ethical to carry
out a randomized trial of hearing protection. The Canadian Task Force previously
recommended primary prevention of noise-induced hearing loss through noise
control programs and hearing protection (A Recommendation).<21> Risk
assessment for hearing loss by history was also recommended (B Recommendation).
When hearing loss is detected, the physician generally refers the patient for a complete audiological examination. Table 1 describes cases where referral is recommended. Where serious or potentially treatable pathology is detected, referral is usually made to an otolaryngologist. A common and readily reversible source of hearing loss is occlusion of the auditory meatus with cerumen.
Recommendations have been made on improving communication with individuals with hearing impairment (see Table 2). In those suitable for amplification, a hearing aid is often helpful. In a randomized controlled trial involving 194 elderly male veterans, subjects were randomly assigned either to receive a hearing aid or to join a waiting list. In those assigned to amplification, significant improvements occurred in social and emotional functions, depression scores, communicative and cognitive abilities by six weeks and continuing to four months.<22> For some patients, a hearing aid tuned to the individual ear with selective amplification of high frequencies, may be preferred.<23> Digital signal processing is a new technique which has shown promise for improving speech recognition by the hearing impaired. In patients with moderate sensorineural hearing loss (65 dB) amplitude processing was associated with 10-12% improvement in intelligibility, but no improvement in those with severesensorineural loss of 95 dB. For that group, increasing consonant duration gave a modest (5%) benefit in intelligibility.<24>
Predicting who will accept amplification is a challenge because up to 50% of older individuals will not accept a hearing aid. Certain questions which explore self-perceived hearing handicap such as "Do you find it difficult to follow a conversation if there is a background noise, e.g. television, radio, children playing?" may help to distinguish those more likely to accept amplification.<25,26>
Recommendations of Others
Breslow and Somers recommend audiometry for adults
every 5 years.<27> The U.S. Preventive Services Task Force previously
recommended that "elderly patients should be evaluated regarding their
hearing, counselled regarding the availability and use of hearing aids,
and referred appropriately for any abnormalities";<28> these recommendations
are presently under review. Mulrow & Lichtenstein recommend screening
of elderly adults using the audioscope as the maneuver of choice.<29>
Conclusions and Recommendations
Hearing loss is a common problem in older individuals,
associated with significant physical, functional and mental health consequences.
The prevalence increases with age, and while many older people are aware
of disability, a significant proportion are not. Screening maneuvers such
as a single question and the use of an audioscope are sensitive and easily
performed in the primary care setting. When hearing loss is detected, strategies
to enhance communication have been suggested, but have not been critically
evaluated.
On the other hand, hearing amplification has been demonstrated to improve the quality of life in a variety of domains although it is unclear whether these results can be generalized to other populations. Factors which predict acceptance of a hearing aid have not been adequately defined. Those wearing hearing aids should be reviewed periodically by an audiologist. Overall, there is fair evidence to include screening for hearing impairment in the periodic health examination in the elderly (B Recommendation) and good evidence to support noise control and hearing protection programs (A Recommendation).
Unanswered Questions (Research
Agenda)
The following have been identified as research
priorities:
This review was initiated in March 1993 and recommendations were finalized by the Task Force in March 1994.
Acknowledgements
The Task Force thanks Susan Whiteside, MClSc,
Senior Audiologist, Chedoke-McMaster Hospital, Hamilton, Ontario and Sharon
M. Abel, PhD, Senior Staff Scientist, Division of Clinical Epidemiology
and Professor of Otolaryngology, University of Toronto, Toronto, Ontario.
Table 1: Recommendations for referral to audiologist
Table 2: Communication Strategies