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Randomized Trial of Amplification Strategies
Bevan Yueh, MD;
Pamela E. Souza, PhD, CCC-A;
Jennifer A. McDowell, MS;
Margaret Patricia Collins, MS, CCC-A;
Carl F. Loovis, PhD, CCC-A;
Susan C. Hedrick, PhD;
Scott D. Ramsey, MD, PhD;
Richard A. Deyo, MD, MPH
Arch Otolaryngol Head Neck Surg. 2001;127:1197-1204.
ABSTRACT
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Background Little is known about quality of life after the use of specific types
of hearing aids, so it is difficult to determine whether technologies such
as programmable circuits and directional microphones are worth the added expense.
Objective To compare the effectiveness of an assistive listening device, a nonprogrammable
nondirectional microphone hearing aid, with that of a programmable directional
microphone hearing aid against the absence of amplification.
Design Randomized controlled trial.
Setting Audiology clinic at the VA Puget Sound Health Care System, Seattle,
Wash.
Patients Sixty veterans with bilateral moderate to severe sensorineural hearing
loss completed the trial. Half the veterans (n = 30) had hearing loss that
the Veterans Affairs clinic determined was rated as "service connected," which
meant that they were eligible for Veterans Affairs–issued hearing aids.
Intervention Veterans with non–service-connected hearing loss, who were ineligible
for Veterans Affairs–issued hearing aids, were randomly assigned to
no amplification (control arm) or to receive an assistive listening device.
Veterans with service-connected loss were randomly assigned to receive either
the nonprogrammable hearing aid that is routinely issued ("conventional")
or a programmable aid with a directional microphone ("programmable").
Main Outcome Measures Hearing-related quality of life, self-rated communication ability, adherence
to use, and willingness to pay for the amplification devices (measured 3 months
after fitting).
Results Clear distinctions were observed between all 4 arms. The mean improvement
in hearing-related quality of life (Hearing Handicap Inventory for the Elderly)
scores was small for control patients (2.2 points) and patients who received
an assistive listening device (4.4 points), excellent for patients who received
a conventional device (17.4 points), and substantial for patients who received
a programmable device (31.1 points) (P<.001 by
the analysis of variance test). Qualitative analyses of free-text diary entries,
self-reported communication ability (Abbreviated Profile of Hearing Aid Benefit)
scores, adherence to hearing aid use, and willingness to pay for replacement
devices showed similar trends.
Conclusions A programmable hearing aid with a directional microphone had the highest
level of effectiveness in the veteran population. A nonprogrammable hearing
aid with an omnidirectional microphone was also effective compared with an
assistive listening device or no amplification.
INTRODUCTION
HEARING LOSS is one of the most common chronic illnesses in the United
States, especially in elderly persons. It affects more than 25% of Americans
older than 65 years.1-2 Rates
are even higher in men; more than 40% of the men in the Framingham cohort
aged 65 to 70 reported hearing impairment, and this proportion increases to
more than 80% of men between the ages of 85 and 90.3
The diminished ability to communicate or appreciate music is frustrating in
and of itself, but the strong association of hearing loss with depression
and functional decline adds further to the burden on the hearing impaired.4-9
There is strong evidence that hearing aids significantly improve quality
of life for patients with sensorineural hearing loss.10-12
In a seminal randomized clinical trial10 of
194 elderly veterans with bilateral hearing loss at the San Antonio Veterans
Affairs (VA) Hospital, San Antonio, Tex, patients were randomly assigned to
receive a hearing aid or to join a waiting list. After 4 months, significant
improvements in social and emotional function, communication function, and
depression were seen in hearing aid recipients compared with those in the
control group. In a follow-up study,11 the
researchers found that the improvements were sustained 1 year after hearing
aid fitting. A separate randomized trial12
confirmed the quality-of-life benefits of hearing amplification. In this study,
180 elderly hearing-impaired persons were offered a hearing aid only, an assistive
listening device (ALD) only, a combination of the hearing aid and the ALD,
or no amplification, in random order. The most significant improvements in
emotional and social function were noted for patients who received the hearing
aid.
However, the relative impact of different types of hearing aids on quality
of life is less clear. With advances in hearing aid technology resulting in
an array of products with varying features and expense, more information about
the relative effectiveness of different hearing aids is needed to help clinicians
provide informed treatment recommendations. Programmable and digital circuits,
multiple memories and channels, and directional microphones are relatively
new technologies, and little is known about how, or even whether, these features
affect outcomes. Several trials13-17
on digital aids have been published, but methodological limitations and reliance
on laboratory measures hamper efforts to determine whether this technology
results in improved quality of life.18
Recent attention has also focused on directional microphones, which
allow selective amplification of sounds from one direction (eg, the amplification
of noises directly in front [and suppression of noises in back] of the hearing
aid user). Subjects from a recent study19 compared
their own nondirectional analog hearing aids with 2 digital aids, one with
a directional microphone and the other without a directional microphone. The
digital aid with the directional microphone was preferred, but no differences
were noted between the nondirectional digital aid and the patients' analog
aids. The researchers concluded that the directional microphone was responsible
for the preference. Gravel et al20 confirmed
the listening advantages offered by directional microphones in a comparison
of nondirectional and directional microphones in hearing-impaired children.
Unfortunately, neither study gave patients the opportunity to wear the aids
at home, so conclusions were based on laboratory measures alone.
The distinction between laboratory and "real-life" outcomes is important,
because it is at the heart of the difference between efficacy and effectiveness
studies. Efficacy studies measure the degree of benefit that a carefully defined
group of patients in an experimental setting receives for treatment under
ideal conditions. Effectiveness reflects the benefit received by typical community
patients under ordinary conditions for the treatment under usual circumstances.21-22 For example, the hearing aid that
significantly improves word recognition scores in a sound booth, but lies
unused in the bottom of a drawer at home, is highly efficacious but ineffective.
Efficacy and effectiveness are important, and investigators must decide which
concept to emphasize. It is our belief that although efficacy is important
to demonstrate, effectiveness is ultimately what matters most to patients.
Thus, we chose to measure effectiveness in this pilot study, which is
part of a long-term project to examine the cost-effectiveness of hearing amplification.
The initial step in a cost-effectiveness analysis is to establish differential
effectiveness, after which the economic analyses may begin. We chose to compare
the relative effectiveness of an ALD, a nonprogrammable hearing aid routinely
issued at the VA Puget Sound Health Care System, Seattle, Wash ("conventional
aid"), and a programmable aid with a directional microphone ("programmable
aid") against the absence of amplification. The primary comparison of interest
was the relative effectiveness of the 2 hearing aids, and our hypothesis was
that typical use of the programmable aid would result in better outcomes than
use of the standard aid.
PATIENTS AND METHODS
PATIENT POPULATION
Patients aged 50 years or older were recruited from those seeking diagnostic
visits or hearing aid evaluations at the audiology clinic of VA Puget Sound
Health Care System. Patients were included if they had symmetric, bilateral,
sensorineural hearing loss. To maximize the homogeneity of hearing loss, however,
strict exclusion criteria were applied:
- Asymmetric hearing loss. For frequencies between
500 Hz and 3 kHz (0.5, 1.0, 1.5, 2.0, and 3.0 kHz), this was defined as any
of the following differences between ears: a 20-dB difference or greater at
1 or more frequencies, a 15-dB difference or greater at 2 or more frequencies,
or a 10-dB difference or greater at 3 or more frequencies.
- Conductive hearing loss. This type of loss was
defined as a 10-dB air-bone gap or greater at any frequency from 500 to 3000
Hz.
- Loss other than mild to moderately severe. Patients
with pure-tone thresholds outside the following range in either ear were excluded:
500 Hz, 10- to 40-dB hearing loss; 1000 Hz, 15- to 50-dB hearing loss; 2000
Hz, 30- to 60-dB hearing loss; and 3000 Hz, 40- to 75-dB hearing loss.
- Upsloping hearing loss of 5 dB per octave or greater
between 500 and 3000 Hz.
- Poor word recognition (discrimination) scores,
defined as Maryland consonant-noun-consonant (CNC) scores (tested 10 dB above
the 3000-Hz threshold) of 80% or worse in either ear.
- Atypical causes of sensorineural hearing loss,
such as ototoxicity, sudden sensorineural loss, or Meniere disease.
Patients were also excluded if they had any of the following: prior
hearing aid experience, poor cognitive function (a score of  23 on the
Mini-Mental State Examination),23 or poor manual
dexterity (judgment by audiologists about the ability to change hearing aid
batteries).
Informed consent was obtained from patients meeting the study criteria.
No remuneration was provided. Enrollment began on October 1, 1998, and was
completed on September 30, 1999.
RANDOMIZATION
The Veterans Health Administration provides hearing aids only to patients
whose hearing loss is judged to be "service connected." Therefore, veterans
with non–service-connected hearing loss, who are ineligible for VA–issued
hearing aids, were randomly assigned to no amplification (control arm) or
to receive an ALD. Veterans with service-connected hearing loss were randomly
assigned to receive either the nonprogrammable hearing aid that is routinely
issued (conventional aid) or a programmable aid with a directional microphone
(programmable aid) (Figure 1). The
strict audiometric inclusion criteria previously detailed were used to maximize
homogeneity of the hearing loss between service-connected and non–service-connected
patients.
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Figure 1. Schematic of the hearing aid trial.
VA indicates Veterans Affairs.
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Randomization was performed in blocks of 4, with separate randomization
for patients aged 50 to 65 years and patients older than 65 years to ensure
relatively similar age distributions between treatment arms. Sealed envelopes
were opened after enrollment and completion of baseline questionnaires and
interviews. No blinding was feasible, given the obvious differences between
hearing amplification devices. The construction of study and placebo devices
would have required additional funding. Patients receiving hearing aids were
told explicitly that there was no evidence that either aid was superior. Audiologists
and study personnel were instructed to avoid describing differences between
the 2 types of hearing aids to the patients.
HEARING AIDS
All patients were fit bilaterally with half-shell in-the-ear analog
hearing aids. Hearing aid selection and fitting were conducted by VA audiologists.
Because we were interested in hearing aid effectiveness, we allowed the audiologists
to make decisions about the fitting requirements within the bounds of the
experimental design. For example, the audiologist was free to order amplification
options (eg, potentiometers, telecoil, canal length, and venting) as appropriate
for each patient, with the following constraints.
The conventional hearing aid was a nonprogrammable nondirectional aid.
Target gain was calculated using the National Acoustic Laboratories'–Revised
prescriptive procedure.24 Probe microphone
measures were used to ensure that the frequency-gain response provided an
acceptable match to target. Each aid had a manual volume control. Output limiting
was accomplished using compression limiting, with the compression threshold
individually adjusted based on each patient's loudness discomfort levels.
The programmable hearing aid had a switchable directional microphone
and remote control. Volume control and 3 memories were available to the patient
via the remote control. The first memory was set for quiet listening using
a nondirectional microphone, with target gain calculated using the National
Acoustic Laboratories'–Revised prescriptive formula. Probe microphone
measures were used to ensure that the frequency-gain response provided an
acceptable match to target. The second and third memories were set by the
audiologist as appropriate for the patient's communication needs. Typically,
the second memory was adjusted to maximize speech understanding in background
noise with the directional microphone, and the third memory was set for comfort
in noise with the directional microphone.
In each case, patients received routine instructions on the use, care,
and function of the hearing aid. All patients were seen for routine clinical
follow-up, including counseling and adjustments as needed, 1 month after the
hearing aid fitting.
DATA COLLECTION
Data were collected via individual interviews and through self-administered
questionnaires at baseline before randomization, and then again at 1 and 3
months after receiving the hearing amplification device (Table 1). (Assistive listening devices were given to the patients
the day of randomization. Hearing aids were fitted 4-6 weeks after randomization.)
The questionnaires were mailed to patients 1 week before the follow-up interviews.
In addition to the interviews and self-administered questionnaires, patients
were asked to maintain a hearing diary for the duration of the study. Patients
recorded the number of hours they used their hearing amplification device
each day (amplification arms) or the number of hours each day that they encountered
hearing-related difficulties (control arm). Patients who did not receive hearing
aids were given their diaries on the day of randomization. Patients who received
hearing aids received their diaries on the day they were fitted with their
aids. The following assessments were made.
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Table 1. Timing of Data Collection*
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Audiometric Data
Unaided air conduction thresholds were recorded at 250, 500, 1000, 2000,
3000, 4000, 6000, and 8000 Hz, and bone conduction thresholds were recorded
at 250 through 4000 Hz. Unaided speech recognition scores were measured using
the Maryland CNC protocol28 at 10 dB above
the 3000-Hz air conduction threshold.
Hearing-Related Quality of Life
"Quality of life" is increasingly common to consider in hearing aid
studies, although there is no precise agreement over its definition and how
to measure it. However, there is general agreement that health-related quality
of life should include assessments of physical, social, and emotional function.
We used 2 separate approaches to measure these functions.
First, we used an outcome measure (instrument) called the Hearing Handicap
Inventory for the Elderly (HHIE), a 25-item hearing-related quality-of-life
scale with 2 subscales that measure the emotional and social impact of hearing
loss.25 The scale is scored from 0 to 100,
with 100 representing the least handicap. A 9-point change in the HHIE score
represents a clinically significant change.29
Second, we performed a qualitative ("clinimetric") analysis of open-ended
comments from the diaries.30 Open-ended text
comments were organized into categories of quality-of-life issues, for which
a taxonomy was developed. The frequency was tallied for taxonomy issues raised
by individual patients.
Self-rated Communication Ability
This was assessed using 2 different validated outcome measures. The
first was the Abbreviated Profile of Hearing Aid Benefit, a 24-item scale
used to measure self-rated communication ability.26
There are 4 subscales in this measure, each of which is scored on a 100-point
scale. We have chosen to represent worst scores as 0 and best scores as 100,
so that a positive incremental score will represent an improvement in function.
The first 3 subscales—ease of communication, background noise, and reverberation—reflect
how well patients understand speech in various listening situations. An intervention
that improves the scores of all 3 subscales by at least 5 points is considered
to be clinically important.31 The fourth subscale
measures aversion to amplified sounds.
The second measure was the revised Denver Scale of Communication Function,32 a 5-item instrument that reflects patients' attitudes
about their communication abilities. This scale was shortened from the original
version,27 and is scored from 1 (worst) to
5 (best), but no numerical anchors for what would represent a clinically important
difference have been established.
Adherence Data
Patients recorded in their diary the number of hours they used their
amplification device each day.
Willingness-to-Pay Data
Willingness to pay is an economic construct popularized by health services
researchers. It measures how much patients value a particular treatment (or
health state). In its simplest form, patients are literally asked how much
they would be willing to pay to have a treatment. We asked patients at their
last visit, "If you lost your hearing device, how much would you be willing
to pay to replace it?" Monthly incomes were recorded to adjust for variation
in income.
DATA ANALYSIS
Outcome measures were scored using published algorithms.25-26,32
The qualitative (clinimetric) analysis was performed by tallying the frequency
with which taxonomy issues were raised by patients in their diaries. Data
were entered into a database (Microsoft Access; Microsoft, Seattle, Wash)
with double-entry verification techniques to ensure accuracy. Age, pure-tone
thresholds, and pure-tone average were analyzed for baseline differences using
an analysis of variance (ANOVA). Dimensional (continuous) data were summarized
using mean incremental differences between baseline and 3-month scores. The
incremental scores were compared with t tests for
pairwise comparisons and an ANOVA for multiple comparisons. Comparisons of
dichotomous (frequency) data were analyzed with  2 tests. Because
multiple comparisons were used, we have highlighted only results that were
statistically significant at  = .01. Statistical analyses were performed
with SAS statistical software, version 6.12 (SAS Institute Inc, Cary, NC).
RESULTS
Demographic and baseline characteristics are shown in Table 2. The mean hearing thresholds for each group are shown in Figure 2. There were no significant differences
in hearing sensitivity between groups for either ear. Of 64 patients enrolled
in the trial, 60 completed the final 3-month follow-up visits. (One patient
in the programmable aid arm died unexpectedly, and 3 others—1 in the
programmable arm and 2 in the standard arms—were unwilling to return
for their 3-month follow-up visits.) All patients were men. No statistically
significant differences for age or degree of hearing loss at baseline were
noted between arms. To correct for minor variations in baseline scores for
some outcome variables, mean incremental results are reported (scores at baseline
subtracted from those at 3 months).
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Table 2. Baseline Characteristics of the Cohort*
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Figure 2. Mean hearing thresholds for each
patient group. A, Right ear. B, Left ear. HL indicates hearing loss; ALD,
assistive listening device.
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HEARING-RELATED QUALITY OF LIFE
Outcome Measures
The type of amplification strongly influenced HHIE scores. Table 3 lists incremental changes in HHIE
scores from baseline to the 3-month follow-up. (Scores are reported so that
positive values reflect improvement and negative values reflect worsening.)
The overall HHIE score, which ranged from 0 to 100, did not change significantly
in either the control or the ALD arm. However, it improved by 17 points in
patients using the standard aid and by more than 31 points in patients using
the programmable aid. One-way ANOVA testing was highly significant, and a
1-tailed t test demonstrated that the difference
between the standard and programmable arms was statistically significant (P = .05). Patients in both hearing aid arms improved by
more than the 9 points that are thought to represent clinically significant
change,29 and the difference between the 2
hearing aid arms was also clinically significant.
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Table 3. Incremental Change in Overall HHIE and Domain Scores*
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Qualitative Analysis
Clear differences were apparent from the clinimetric analysis of open-ended
diary comments as well. A taxonomy of quality-of-life issues was developed
through an iterative process by consensus (B.Y. [an otolaryngologist] and
P.E.S., M.B.S., and C.F.L. [audiologists]), who were content experts. The
taxonomy is divided into 2 major categories. The first addresses intrinsic
issues of hearing loss, such as functional, emotional, and social impairment.
The second covers extrinsic factors associated with the hearing aid itself,
including the acoustics of amplification, the physical comfort of the aid,
the convenience of the aid, maintenance and reliability of the aid, cosmetic
appearance and self-esteem with the aid, and satisfaction with technological
features. Table 4 lists the number
(percentage) of patients in each arm who raised selected issues. In general,
positive (favorable) comments occurred more often as the technology became
more advanced, and negative (unfavorable) comments occurred less often. This
pattern was seen in most categories, although no differences were seen in
the physical comfort and appearance domains between hearing aid arms (the
physical sizes of the shells were similar).
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Table 4. Analysis of Diary Comments About Hearing-Related Quality of
Life*
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SELF-RATED COMMUNICATION ABILITY
The type of amplification also strongly influenced incremental scores
of the Abbreviated Profile of Hearing Aid Benefit and the revised Denver Scale
of Communication Function (Table 5).
Overall Abbreviated Profile of Hearing Aid Benefit scores improved minimally
in the control arm, but increased by more than 16 points in the programmable
aid arm (P = .01, ANOVA). The changes were clinically
significant in the amplification arms, because the domain scores improved
by more than 5 points in the ease of communication, background noise, and
reverberation subscales. Interestingly, although patients using the standard
aid had more aversion to amplified sounds, this difference was not present
in patients with the programmable aid. The revised Denver Scale of Communication
Function scores improved considerably in the hearing aid arms, with essentially
no change in the non–hearing aid arms.
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Table 5. Incremental Change in Self-rated Communication Ability*
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ADHERENCE DATA
Self-reported adherence to use of the hearing devices also varied significantly
between arms (Figure 3). Patients
used the programmable hearing aid an average of 8.8 h/d, and the standard
hearing aid an average of 6.9 h/d (P<.001, t test). Patients were clearly less adherent to the ALD,
with 0.6 h/d of average use (P<.001, t test between the control arm and each hearing aid arm). The graphical
data show that the initial separation between the programmable and standard
arms became less apparent as the study progressed. Several explanations are
possible. First, it is possible that differential acclimatization to the standard
aid may have closed the gap. Second, this may be a spurious result because
of response bias. Response bias would occur if patients who are less adherent
are also less likely to complete diary entries. In this study, there were
fewer diary entries toward the end of the trial. If patients who were less
adherent were less likely to continue completing diary entries, the calculated
mean hours of daily use would be artificially elevated for the device to which
patients were more adherent.
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Figure 3. Self-reported use for each hearing
device, as a function of the time after fitting. ALD indicates assistive listening
device.
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WILLINGNESS-TO-PAY DATA
Substantial differences between treatment arms were also noted for willingness-to-pay
data. When patients were asked how much they would be willing to pay to have
their amplification devices replaced if they lost them, patients using the
ALD (n = 15) offered a mean of $40 (range, $0-$500), or 1% of their monthly
income, to replace the device. Patients using standard aids (n = 14) said
that they would be willing to pay a mean of $800 (range, $0-$3500), or approximately
29% of their monthly income. Patients who received the programmable aids (n
= 16) indicated they would pay a mean of $2240 (range, $0-$5000), or approximately
78% of their monthly income.
COMMENT
In this randomized trial comparing the effectiveness of 3 amplification
strategies against a control arm, clear treatment effects were apparent. Both
hearing aids were superior to an ALD and the absence of amplification in all
measures of outcome. These observations confirm the results of prior randomized
trials comparing the use of a hearing aid against either no intervention10-11 or an ALD.12
Of greater interest is that we established differential treatment effectiveness
between hearing aids, which, to our knowledge, has not been done previously.
The programmable hearing aid with a directional microphone performed better
than the standard nonprogrammable aid did. Results were particularly convincing
for quality-of-life and willingness-to-pay data. The next logical step is
to perform the cost-effectiveness analyses that will help determine if the
improved effectiveness is worth the added expense.
We did not use blinding in this study. Blinding observers and subjects
to different types of hearing aids, unlike medications and even selected surgical
procedures, is difficult. In some cases, blinding is impossible (eg, consider
the study that wants to address the effect of hearing aid size on satisfaction).
Even when features can be disguised, substantial investments in expensive
study and placebo hearing aids are required. A separate consideration is whether
blinding is desired. Blinding is integral to the traditional randomized efficacy
trial but is less important in effectiveness studies, because patients are
supposed to be aware of the type of treatment they are receiving (just as
they would be in real life). The obvious disadvantage is that effectiveness
studies may be susceptible to bias. On the other hand, we explicitly chose
to measure effectiveness (eg, quality of life and adherence to use), because
this is ultimately what matters to patients and their physicians.21-22
The consistent findings among outcome measures suggest that our results
are robust. However, we cannot state which features were responsible for the
observed improvements in effectiveness. Although the sizes of the 2 hearing
aid molds were similar, budget limitations forced us to simultaneously compare
several technologies, such as directional microphones, programmability, and
multiple memories. Future efforts will be directed toward isolating the effects
of one hearing aid feature at a time.
This study has several other limitations. First, only patients with
bilateral, symmetric, mild to moderately severe sensorineural loss were included.
The results may not be applicable to patients with other types of hearing
loss. Second, 2 populations (patients with service-connected and non–service-connected
hearing loss) were used at baseline. The inclusion criteria were designed
to maximize homogeneity between the 2 populations, but comparisons between
non–hearing aid and hearing aid arms may be subject to unknown biases.
However, we emphasize that the primary comparison of interest (nonprogrammable
vs programmable aids) was made in the same population (patients with service-connected
hearing loss only).
CONCLUSIONS
Hearing aids, and the programmable aid with the directional microphone
in particular, were substantially more effective in this randomized trial.
This conclusion was supported by 2 forms of hearing-related quality-of-life
data (outcome measures and qualitative analyses), self-rated communication
ability, adherence to hearing device use, and willingness-to-pay data.
Cost-effectiveness analyses are needed to understand the trade-offs
between improved effectiveness and added expense of the programmable aid with
the directional microphone.
We cannot state which features are responsible for the improvements
in effectiveness. Future definitive randomized efficacy and effectiveness
trials are needed to evaluate features such as digital processing and directional
microphones to identify the technologies that are truly responsible for improved
effectiveness.
AUTHOR INFORMATION
Accepted for publication June 11, 2001.
This study was supported by Career Development Award CD-98318 from the
Health Services Research and Development Service, Veterans Health Administration,
Department of Veterans Affairs, Seattle, Wash (Dr Yueh).
Presented at the meeting of the American Auditory Society, Scottsdale,
Ariz, April 8, 2000.
We thank the following audiologists at the VA Puget Sound Health Care
System for their enthusiastic participation: Kathryn-Anne Anselmi, Marilyn
Dille, Billie Garber, June Hensley, Eric James, Paula Johnston, Sami Styer,
Hope Weaver, and Leah Wilkinson.
The views expressed in this article are those of the authors and do
not necessarily represent the views of the Department of Veterans Affairs.
Corresponding author and reprints: Bevan Yueh, MD, Surgery Service
(112OTO), VA Puget Sound Health Care System, 1660 S Columbian Way, Seattle,
WA 98108 (e-mail: byueh{at}u.washington.edu).
From the Health Services Research and Development Service (Drs Yueh
and Hedrick and Ms McDowell), the Surgery and Perioperative Care Service (Dr
Yueh), and the Rehabilitation Care Service (Ms Collins and Dr Loovis), VA
Puget Sound Health Care System, Seattle, Wash; and the Center for Cost and
Outcomes Research (Drs Yueh, Ramsey, and Deyo) and the Departments of Otolaryngology/Head
and Neck Surgery (Dr Yueh), Speech and Hearing Sciences (Dr Souza), Health
Services (Drs Yueh, Hedrick, Ramsey, and Deyo), and Internal Medicine (Drs
Ramsey and Deyo), University of Washington, Seattle.
REFERENCES
| |
1. US Department of Commerce. Statistical Abstract of the United States. 117th ed. Washington, DC: US Dept of Commerce; 1997.
2. Cruickshanks KJ, Wiley TL, Tweed TS, et al. Prevalence of hearing loss in older adults in Beaver Dam, Wisconsin:
the Epidemiology of Hearing Loss Study. Am J Epidemiol. 1998;148:879-886.
FREE FULL TEXT
3. Gates GA, Cooper JC Jr, Kannel WB, Miller NJ. Hearing in the elderly: the Framingham cohort, 1983-1985, part I: basic
audiometric test results. Ear Hear. 1990;11:247-256.
ISI
| PUBMED
4. Kay DW, Roth M, Beamish P. Old age mental disorders in Newcastle upon Tyne, II: a study of possible
social and medical causes. Br J Psychol. 1964;110:668-682.
5. Herbst KG, Humphrey C. Hearing impairment and mental state in the elderly living at home. BMJ. 1980;281:903-905.
6. LaForge RG, Spector WD, Sternberg J. The relationship of vision and hearing impairment to one-year mortality
and functional decline. J Aging Health. 1992;4:126-148.
FREE FULL TEXT
7. Carabellese C, Appollonio I, Rozzini R, et al. Sensory impairment and quality of life in a community elderly population. J Am Geriatr Soc. 1993;41:401-407.
ISI
| PUBMED
8. Appollonio I, Carabellese C, Frattola L, Trabucchi M. Effects of sensory aids on the quality of life and mortality of elderly
people: a multivariate analysis. Age Ageing. 1996;25:89-96.
FREE FULL TEXT
9. Mulrow CD, Aguilar C, Endicott JE, et al. Association between hearing impairment and the quality of life of elderly
individuals. J Am Geriatr Soc. 1990;38:45-50.
ISI
| PUBMED
10. Mulrow CD, Aguilar C, Endicott JE, et al. Quality-of-life changes and hearing impairment: a randomized trial. Ann Intern Med. 1990;113:188-194.
11. Mulrow CD, Tuley MR, Aguilar C. Sustained benefits of hearing aids. J Speech Hear Res. 1992;35:1402-1405.
12. Jerger J, Chmiel R, Florin E, Pirozzolo F, Wilson N. Comparison of conventional amplification and an assistive listening
device in elderly persons. Ear Hear. 1996;17:490-504.
ISI
| PUBMED
13. Knebel SB, Bentler RA. Comparison of two digital hearing aids. Ear Hear. 1998;19:280-289.
ISI
| PUBMED
14. Arlinger S, Billermark E, Oberg M, Lunner T, Hellgren J. Clinical trial of a digital hearing aid. Scand Audiol. 1998;27:51-61.
FULL TEXT
|
ISI
| PUBMED
15. Boymans M, Dreschler WA, Schoneveld P, Verschuure H. Clinical evaluation of a full-digital in-the-ear hearing instrument. Audiology. 1999;38:99-108.
ISI
| PUBMED
16. Valente M, Sammeth CA, Potts LG, Wynne MK, Wagner-Escobar M, Coughlin M. Differences in performance between Oticon MultiFocus Compact and ReSound
BT2-E hearing aids. J Am Acad Audiol. 1997;8:280-293.
PUBMED
17. Valente M, Fabry DA, Potts LG, Sandlin RE. Comparing the performance of the Widex SENSO digital hearing aid with
analog hearing aids. J Am Acad Audiol. 1998;9:342-360.
PUBMED
18. Yueh B. Clinical challenges in otolaryngology: digital hearing aids. Arch Otolaryngol Head Neck Surg. 2000;126:1394-1397.
FREE FULL TEXT
19. Valente M, Sweetow R, Potts LG, Bingea B. Digital versus analog signal processing: effect of directional microphone. J Am Acad Audiol. 1999;10:133-150.
20. Gravel JS, Fausel N, Liskow C, Chobot J. Children's speech recognition in noise using omni-directional and dual-microphone
hearing aid technology. Ear Hear. 1999;20:1-11.
21. Brook RH, Lohr KN. Efficacy, effectiveness, variations, and quality: boundary-crossing
research. Med Care. 1985;23:710-722.
ISI
| PUBMED
22. Flay BR. Efficacy and effectiveness trials (and other phases of research) in
the development of health promotion programs. Prev Med. 1986;15:451-474.
FULL TEXT
|
ISI
| PUBMED
23. Folstein MF, Folstein SE, McHugh PR. "Mini-Mental State": a practical method for grading the cognitive state
of patients for the clinician. J Psychiatr Res. 1975;12:189-198.
FULL TEXT
|
ISI
| PUBMED
24. Byrne D, Dillon H. The National Acoustic Laboratories' (NAL) new procedure for selecting
the ga |
