Negative consequences of uncorrected hearing loss - A review

Abstract

Hearing loss gives rise to a number of disabilities. Problems in recognizing speech, especially in difficult environments, give rise to the largest number of complaints. Other kinds of disabilities may concern the reduced ability to detect, identify and localize sounds quickly and reliably. Such sounds may be warning or alarm signals, as well as music and birds singing. The communicative disability affects both hearing-impaired people and other people in their environment--family members, fellow workers, etc. Hearing-impaired people are not always aware of all the consequences of the impairment; they do not always know what they are missing. Several studies have shown that uncorrected hearing loss gives rise to poorer quality of life, related to isolation, reduced social activity, and a feeling of being excluded, leading to an increased prevalence of symptoms of depression. These findings indicate the importance of early identification of hearing loss and offers of rehabilitative support, where the fitting of hearing aids is usually an important component. Several studies also point to a significant correlation between hearing loss and loss of cognitive functions. Most of these studies show such a correlation without being able to show whether the hearing loss caused the reduction in cognitive performance or if both the hearing loss and the cognitive decline are parts of a common, general age-related degeneration. A couple of these studies, however, indicate that the uncorrected hearing loss may be the cause of cognitive decline. Whichever alternative is true, the correlation should be seen as a clear indication for early hearing aid fitting for those needing it. Monaural hearing aid fitting in subjects with bilateral hearing loss may give rise to a reduced ability to recognize speech presented to the unaided ear, the so-called late-onset auditory deprivation effect. This functional decline is reversible in some but not all subjects after fitting of a hearing aid also on the previously unaided ear.

Full text

Stig Arlinger
Department of Audiology,
University Hospital,
S-581 85 Linköping, Sweden
E-mail:
Disability and handicap
Hearing loss is an often underestimated disturbance of a sensory
function. It has been shown to negatively affect physical,
cognitive, behavioural and social functions, as well as general
quality of life, and is clearly related to depression and dementia.
It is estimated that approximately 10% of the population in
many Western countries suffer from a hearing loss of a such
a degree that it affects ordinary daily life. The prevalence of
hearing loss is strongly related to age (Davis, 1995; Rosenhall et
al, 1999).
A lesion in the auditory sense organ can give rise to various
forms of impairment, most commonly hearing loss, tinnitus, or
hyperacusis. In this review, the focus is on hearing loss and the
possibilities of overcoming at least some of its effects by means
of hearing aids.
The kind of lesion that dominates in the developed countries
is the sensorineural lesion, primarily involving the cochlea, with
loss of hair cell function. This kind of lesion gives rise to both
quantitative and qualitative effects, both attenuation and dis-
tortion (Plomp, 1978).
A hearing loss gives rise to disabilities of various kinds, e.g.
loss of ability to detect sounds, to recognize speech, especially
in adverse conditions, and to localize sound sources. In response
to questions about problems in understanding speech in back-
ground noise or reverberation, young normal-hearing people
typically answer ‘rarely’ (Cox, 1996), while people with slight-
to-moderate hearing loss, on average, answer ‘often’ (Cox &
Alexander, 1995). In order for hearing-impaired people to pick
up as much as possible of the acoustical world, they have to
concentrate much more than normal-hearing people. The fatigue
caused by this extra concentration is an additional component
among the consequences of uncorrected hearing loss. The
reduced ability to detect sounds may affect sounds such as those
of doorbells or telephones, traffic sounds that may signal
immediate danger, and sounds of importance for quality of life,
such as music or bird song.
Disability may in turn give rise to handicap or, in other
terminology, affect the hearing-impaired person’s participation
in interactions with other people. Increasing difficulties in
recognizing the spoken messages of others, having to ask for
repetition too often, and still not being sure about having
understood correctly, often lead to withdrawal from social
activities, rejection of invitations to parties, and no more visits
to theatres, cinemas, churches, lectures, etc. This, in turn, leads
to reduced intellectual and cultural stimulation, and an in-
creasingly passive and isolated social citizen.
In a German study (Kiessling et al, 1996), a group of 99
subjects of various ages with slight-to-moderate hearing loss
were asked to fill in a questionnaire, the Gothenburg Profile,
which assesses both disability and handicap caused by the
Original Article
International Journal of Audiology 2003; 42:2 S17–2 S20
Negative consequences of uncorrected
hearing loss––a review
Stig Arlinger
Department of Audiology,
University Hospital,
Linköping, Sweden
Key Words
Hearing loss
Speech communication
Quality of life
Depression
Cognitive functions
Auditory deprivation
?
Abstract
Hearing loss gives rise to a number of disabilities. Problems in recognizing speech, especially in difficult
environments, give rise to the largest number of complaints. Other kinds of disabilities may concern the
reduced ability to detect, identify and localize sounds quickly and reliably. Such sounds may be warning
or alarm signals, as well as music and birds singing. The communicative disability affects both hearing-
impaired people and other people in their environment—family members, fellow workers, etc. Hearing-
impaired people are not always aware of all the consequences of the impairment; they do not always
know what they are missing. Several studies have shown that uncorrected hearing loss gives rise to
poorer quality of life, related to isolation, reduced social activity, and a feeling of being excluded,
leading to an increased prevalence of symptoms of depression. These findings indicate the importance
of early identification of hearing loss and offers of rehabilitative support, where the fitting of hearing
aids is usually an important component. Several studies also point to a significant correlation between
hearing loss and loss of cognitive functions. Most of these studies show such a correlation without being
able to show whether the hearing loss caused the reduction in cognitive performance or if both the
hearing loss and the cognitive decline are parts of a common, general age-related degeneration. A
couple of these studies, however, indicate that the uncorrected hearing loss may be the cause of cognitive
decline. Whichever alternative is true, the correlation should be seen as a clear indication for early
hearing aid fitting for those needing it. Monaural hearing aid fitting in subjects with bilateral hearing
loss may give rise to a reduced ability to recognize speech presented to the unaided ear, the so-called
late-onset auditory deprivation effect. This functional decline is reversible in some but not all subjects
after fitting of a hearing aid also on the previously unaided ear.

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International Journal of Audiology, Volume 42 Supplement 2
hearing loss. To questions regarding the degree of problems in
recognizing speech, the average response was ‘half the time’. To
questions regarding handicap, focusing on how the hearing loss
affects social interactions with other people, or behaviour and
reactions in various situations, the average answer was ‘now and
then’.
In the USA, Ventry & Weinstein (1982) administered a 25-
item questionnaire to 100 persons above 65 years of age with
varying degrees of hearing loss, from none at all to profound.
The questions concerned two categories—emotional conse-
quences of hearing impairment, and problems and reactions
related to specific situations. On a scale running from 0 to 100,
the subjects with hearing thresholds within normal range scored,
on average, 9.9, those with mild hearing loss scored 23.7, those
with moderate hearing loss scored 42.7, and those with severe-
to-profound hearing loss scored 76.0.
A hearing loss affects communication with other people. Thus,
the effects concern not only hearing-impaired people, but also, to
a high degree, people around them—family, fellow workers, etc.
Also, these people have to put more effort into communication
with the hearing-impaired person: they need to speak more slowly
and with better articulation, turn their face towards the hearing-
impaired person to allow lipreading, and move closer rather than
talking from a distance or from a neighbouring room. As a
consequence of these increased demands, there is a high risk that
people will make less contact with the hearing-impaired person,
who will become still more isolated.
Often, the hearing-impaired person is not clearly aware of all
the consequences of the hearing loss. This may be due to the
slow progress of the loss, which is the typical pattern, as well as
to the fact that the hearing-impaired person does not think of
the existence of all the sounds that have become inaudible. This
is clearly illustrated by the finding often reported by people after
having been fitted with their first hearing aids of rediscovering
sounds the existence of which they had long since forgotten.
Wellbeing and quality of life
As pointed out above, longstanding uncorrected hearing loss
in the elderly often results in withdrawal from a variety of social
activities, which in turn may affect quality of life as well as
mental health and wellbeing. Reduced auditory and intellectual
stimulation may give rise to changes in the central nervous
system, and may affect the development of dementia.
The National Council on the Aging in the USA (Seniors
Research Group, 1999) organized a study in which 2304 elderly
hearing-impaired persons, hearing aid users as well as non-users,
answered a questionnaire. In addition, 2090 significant others of
hearing-impaired people answered another questionnaire. The
results showed that hearing-impaired people who did not use
hearing aids more often stated that they felt sad or depressed,
were worried, showed paranoid tendencies, took part in less
social activity, and experienced more emotional turmoil. Both
the affected people and their significant others reported benefits
from hearing aid use in terms of better relationships at home,
more confidence, and better relationships with others. Family
members reported such benefits more often than the hearing-
impaired people themselves. The most common reasons for not
using hearing aids in this group were that they felt that their
hearing was not bad enough or that they got along without one.
Scherer & Frisina (1998) at the Veterans Administration in
the USA compared two groups, each with 20 subjects in the age
range 60–81 years; one group had normal hearing (average
hearing threshold levels at 1, 2 and 4 kHz 11 dB, range 5–16
dB), while the other group had slight-to-moderate hearing loss
(average 25 dB, range 13–41 dB). Both groups showed normal
cognitive functions. Although the groups were small, the results
showed that even a slight hearing loss gives rise to increased
problems of speech recognition in noise and reduced feeling of
wellbeing.
Cognitive functions
A research group in Berlin, Germany, has reported a series of
studies concerning the correlation between changes in sensory
function with age and intellectual and cognitive functions.
Lindenberger & Baltes (1994) reported on a study of 156
persons in the age range 70–103 years (mean age 85 years). In
the age range 70–84 years, the mean hearing loss (five-frequency
average 0.5–4 kHz) was 50 dB for the men and 44 dB for the
women. In the group above 85 years of age, the corresponding
values were 59 dB and 58 dB, respectively. Only about 17% of
the subjects had access to hearing aids. In addition to hearing
thresholds, visual acuity was tested, and cognitive functions
were assessed by a series of tests. Taken together, the results
from the visual and auditory tests explained close to half of the
total variance and 93% of the age-related variance in the
cognitive tests. The authors interpret these results as support for
a model in which age-related differences in cognitive functions
represent an indirect consequence of age-related differences
in vision and hearing. Sensory function is seen as a strong
predictor in late life of individual differences in intellectual
function. The authors admit, however, that the results may be
interpreted as visual and auditory acuity being very sensitive to
negative age changes in cognitive functions such as attention
and discrimination. Unfortunately, the subgroup that had access
to hearing aids was not compared with those who did not.
A later report from the same authors (Lindenberger & Baltes,
1997) presented the results from an extended group of 516
persons in the same age range, with 16% of the subjects using
hearing aids. The results here essentially confirmed the results
from the previous study: sensory function is significantly cor-
related with cognitive function in elderly persons. The model
that they present suggests that the relationship between age,
sensory function and cognitive function implies that age-related
differences in cognitive functions are so strongly related to
sensory–sensorimotor function (vision, hearing, balance) that
age in itself has no significant effect on cognitive functions after
control for sensory–sensorimotor function.
A third report from the same group (Baltes & Lindenberger,
1997) concerned 687 subjects over the wider age range from 25
to 103 years by complementing the 516 from the previous study
with 171 younger subjects in the age range 25–69 years. None of
the younger subjects used hearing aids. The results showed that
sensory function was a good predictor of age-related differences
in cognitive function, and that the relationship between sensory
function and cognitive function increased with age. The authors
conclude that the mechanisms behind age-related changes in
sensory function are also behind age-related changes in cognitive
function. However, their results still do not allow an interpre-

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Arlinger
Negative consequences of uncorrected
hearing loss––a review
tation in terms of cause and effect, i.e. that reduced sensory
function gives rise to reduced cognitive function through sensory
deprivation.
An Italian study (Appolonio et al, 1996) involved 1192
subjects in the age range 70–75 years in northern Italy. Both
cross-sectional and longitudinal data obtained over a 6-year
period were presented. The subjects were divided into three
groups according to auditory and visual function. Group A (275
subjects) were considered to have normal auditory and visual
acuity, while group B (673 subjects) had reduced visual and/or
auditory acuity with access to correction by glasses and/or
hearing aids. The third group C (244 subjects) had reduced
visual and/or auditory acuity without access to any correction.
Of these, 20 were affected in both vision and hearing, 106 had
hearing loss but normal vision, and 118 had normal hearing but
reduced visual acuity. Socio-economic status, quality of life and
cognitive functions were assessed by means of questionnaires.
Health state was assessed in terms of use of medical care, and
mortality was recorded during the 6-year study period. The
statistical analysis showed significant differences between the
groups. Group C showed significantly poorer outcome than
groups A and B in quality of life and cognitive function. When
controlling for differences in socio-economic factors, significant
differences remained in quality of life between groups B and C
and between groups A and B. The analysis of mortality during
the 6-year period showed a significantly higher mortality rate
among men in group C than among men in group A and group
B after correction for differences in socio-economic status and
general state of health. No differences were found for women.
The conclusion drawn by the authors is that poor health as such
cannot alone explain the differences in mortality between the
men in the three groups in the study, but that auditory and
visual function play an indirect role through their effects on
general physical health and on social relations. They consider
the results as strongly supporting the need to check visual and
auditory functions among the elderly, and to encourage them to
use sensory aids when these functions are reduced.
Cacciatore et al (1999) studied 1332 persons older than
65 years (mean age 74 years) in southern Italy. They assessed
hearing loss, cognitive function, depression and quality of life
by means of questionnaires. Hearing loss was reported by 27%
of the subjects. Use of hearing aids was recorded. A strong
correlation was found between hearing loss and reduced cognitive
function, independent of age and educational level. Also, the
correlation between hearing loss and depression was statistically
significant. Use of hearing aids reduced the symptoms of
depression. Greater hearing loss was associated with reduced
quality of life. The conclusion drawn by the authors is that the
use of hearing aids may have a protective effect against reduced
cognitive function and provide better quality of life for elderly
people.
Similarly, a Japanese study has shown a significant cor-
relation between hearing loss, cognitive function and depression,
based on 747 subjects in the age range 65–98 years (Naramura et
al, 1999). The authors could not draw any conclusions about
cause and effect, however, but suggested that regular checks of
hearing for early detection of hearing loss may contribute to the
preservation of good quality of life among the elderly.
Uhlmann et al (1989), in the USA, investigated a group of 100
elderly (above 65 years) subjects with dementia, and a control
group of equal size, matched for age, gender, and educational
level. Hearing acuity was measured (0.5–3 kHz), and cognitive
function and depression were assessed by means of validated
questionnaires. Hearing aids were used by 17 subjects in the
dementia group and 13 in the control group. Hearing loss was
significantly more common in the test group than in the control
group. The probability of dementia was significantly higher in a
subgroup where hearing loss exceeded 40 dB. The degree of
hearing loss showed a significant correlation with reduced
cognitive function in both the test group and the control group.
This significant correlation remained after control for differences
in age, level of education, gender, medication, and depression.
The authors concluded that their results support the hypothesis
of hearing loss contributing to reduced cognitive function in the
elderly. This, in turn, may increase the symptoms of dementia
and result in reduced functionality. Correcting the hearing loss
by the use of hearing aids cannot be expected to prevent
dementia, but may reduce the consequences of the disease.
A common finding among the reports reviewed above is a
significant correlation between hearing loss and reduced cognitive
function. This makes a study from The Netherlands interesting
(Smits et al, 1999); this showed cognitive function to be signi-
ficantly correlated with the probability of surviving a 5-year
period in a group of 2380 subjects, randomly selected in the age
range 55–85 years. Speed of information processing was the
specific cognitive function that showed the strongest correlation
with mortality. The authors assume a general biological decline
to be the most likely hypothesis to explain the predictive ability
of the cognitive functions.
Mulrow et al (1990) reported on a study concerning 188
elderly persons with hearing loss, in which half of the subjects
were randomly selected for hearing aid fitting, and the other half
were placed on a waiting list for hearing aids. The groups were
comparable with regard to demographic and clinical variables
and degree of hearing loss. Quality of life, depression and
cognitive functions were assessed initially, as well as after
6 weeks and 4 months. Changes over the 4-month period differed
significantly between the two groups. The hearing aid group
reported significant improvements in social, emotional and
communicative functions, as well as in cognitive function and
depression. Also, assessment by significant others regarding
social and communicative function agreed with this.
A later report (Mulrow et al, 1992) concerned 192 elderly
(mean age 72 years) hearing-impaired people over a period of
12 months after the fitting of hearing aids. Using standardized
questionnaires for quality of life, depression and cognitive
function, they found a significantly improved quality of life and
reduced degree of depression; this effect was stable over the
observation period. Cognitive functions showed only small
changes, which returned to baseline after 12 months; however,
only two of the subjects showed significantly reduced cognitive
function.
Late-onset auditory deprivation
A special aspect of untreated hearing loss concerns the auditory
deprivation effect, which may occur in people with bilateral,
essentially symmetrical, hearing loss with only monaural hearing
aid fitting (Arlinger et al, 1996). The effect appears as a reduced
ability to recognize speech presented to the ear that has not been

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International Journal of Audiology, Volume 42 Supplement 2
fitted with a hearing aid and which has therefore been exposed
to significantly less auditory input than the aided ear for a long
time; both ears show essentially identical unchanged pure-tone
hearing thresholds. The first report came from the USA (Silman
et al, 1984). The effect typically appears after one or a few years
of monaural hearing aid use, and has been shown in both
children and adults (Gelfand & Silman, 1993; Hattori, 1993).
After changing to binaural hearing aid fitting, the effect may
disappear completely or partially, but in some cases the effect
may remain despite this. A follow-up study reported on six adult
patients showing the effect but with rather different recovery
patterns after they started using binaural fittings for at least
8 h/day (Gelfand, 1995). Two of the cases showed complete
recovery after 1 year of binaural use. Two other cases showed
partial recovery with remaining asymmetry even after 2 and
5 years of binaural use, respectively. The two remaining cases
showed no recovery even after 5 or 6 years of reported binaural
hearing aid use. No obvious factors could predict the different
recovery patterns. None of the studies reported on binaural
speech recognition in sound fields, and thus it is not known
whether the effect also involves reduced ability to make use of
binaural integration.
Conclusions
Uncorrected hearing loss represents an auditory disability
involving reduced speech recognition ability, especially in difficult
environments, and reduced ability to detect, identify and localize
sounds. This affects the lives of both the hearing-impaired person
and significant others. The hearing-impaired person is not always
aware of all the consequences.
Uncorrected hearing loss gives rise to a poorer quality of life,
related to isolation, reduced social activity, a feeling of being
excluded, and increased symptoms of depression. There is a
significant correlation between uncorrected hearing loss and
reduced cognitive functions. There is no clear proof that hearing
loss is the cause of the reduced cognitive function, but indirect
evidence from some studies supports this hypothesis. If the
hearing loss is indeed a cause of cognitive decline, this is a very
strong argument for early detection of hearing loss and fitting of
hearing aids. However, hearing loss and cognitive decline having
a common cause is also a good reason for early detection and
fitting of hearing aids: The cognitive decline will exacerbate the
consequences of missed information due to the hearing loss. The
more auditory information that is available, the easier it will be
for the impaired cognitive system to process it successfully.
Monaural hearing aid fitting in subjects with bilateral hearing
loss may give rise to a late-onset auditory deprivation effect,
appearing as a reduced ability to recognize speech presented to
the ear that has been deprived of significant auditory stimula-
tion. The effect may or may not be reversible. This is considered
a strong argument for bilateral fitting being the standard
procedure in hearing aid dispensing (Arlinger et al, 1996).
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