Contents
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OverviewBurden
of SufferingHearing 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>
ManeuverThe 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 TreatmentWhen 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 OthersConclusions
and RecommendationsOn 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)EvidenceThis review was initiated in March 1993 and recommendations were finalized by the Task Force in March 1994.
AcknowledgementsTable
1: Recommendations for referral to audiologist
Table
2: Communication Strategies
Link to Structured Abstract of this review
Link to Summary Table of this review
Link to Selected References list of this review
Reprinted in modified format by the Canadian
Task Force on Preventive Health Care
with permission.
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Original Copyright
© 1994 Minister of Supply and Services Canada.
Last modified March 27, 1998.
