DISCUSSION
Our investigation presents data on comparison of different kinds of
sound amplification technology (advanced and basic) for the first time
described in a developing country. It also adds information on the
short-term effect of hearing aids in attention and memory tasks and
auditory evoked latencies, which should encourage further long-term
studies.
The findings of the present study suggest the short-term beneficial
effect of hearing-aid use in older adults who are naive to sound
amplification devices, despite its level of technology [21,22].
With regard to the relationship between auditory deprivation and
cognitive decline [1–5,11–19], it is believed that the use of
hearing aids represents a determinant for improving the quality of life
among hearing-impaired elderly [36]. To date, we have no instrument
that can directly assess cognition as a whole, so we had to rely on
attention and memory skills, as well as auditory evoked potentials
latency to hypothesize so.
The educational level of our sample, comprising older patients who
depend on the public health service, is representative of the majority
of the population of the developing countries such as ours.
Consequently, the findings of this study only represent those countries
with a similar sociodemographic profile. Poor education is considered a
potentially modifiable risk factor for dementia [10], particularly
in countries such as Brazil [37]. Therefore, strategies for
mitigating these risks are vital in these countries, which plays an
effort to minimize cognitive impairment. Given Brazil´s rapidly aging
population, auditory deprivation may constitute a factor that limits the
quality of life of the elderly. Auditory deprivation is held as the main
modifiable factor in adult life capable of preventing cognitive decline
[10]. The role of audiologists and ENT specialists is thus to
minimize hearing deprivation by diagnosing hearing loss as soon as they
can.
The hearing aids we used in this study reflect the different levels of
technology consistent with the devices available at the time of this
clinical trial. Group A used devices of premium technology, including
features of automatic asymmetric directionality, environmental acoustic
gain optimizer (up to 6 dB gain for less noisy environments), and noise
reduction by environment (noise reduction of up to 10 dB in noisy
environments). Group B (basic technology) used hearing aids with fixed
symmetric directionality (omnidirectional OR directional
simultaneously), with no gain optimizer by environment, and offering
maximum noise reduction of 3 dB. Both Groups A and B used default
manufacturer settings (GN group) for wind-noise reduction, microphone
feedback cancelation, and expansion. Group C (placebo) patients, after
using their hearing aids for 12 weeks with no sound amplification, had
their devices programmed according to the same protocol applied for
fitting groups A and B. All the electroacoustic characteristics we
mentioned here are easily found in the technical specifications of the
hearing aids from the GN group (ReSound).
As shown by a previous studies [21,22,38], our results failed to
show any difference between premium and basic hearing aids, which
suggest that amplification plays the major role in restoring hearing
abilities. It is believed that sound signal processing algorithms may
reduce listening effort [16–19], but robust data supporting these
theories are still lacking.
Although we chose a neuropsychological test that was not sensitive
enough for detecting discrete improvements in memory and attention, the
NEUPSILIN was elected for the present study because it is validated for
its use in older Brazilian patients and thus could be applied in our
sample. One of the tests which differed statistically between pre and
post-intervention was the word recognition task. On this task, the
subject hears the spoken words aloud by the examiner and must decide
whether these are part of the list of words they heard earlier in the
test. In this assessment, the patient must deal with phonemic
distractors, thus the sound amplification itself facilitates the
patient’s performance at it. A comparison of the 3 groups revealed that
this difference occurred only between Groups B and C, pointing to a
possible sample size effect.
The definition used by Moore et al. [39] was originally proposed by
Neisser in 1967 and states that cognition is an individual´s ability to
transform sensorial input into meaning. Hearing aids allow the
individuals to perceive sounds again, but the reassignment of meaning to
these sound stimuli is not immediate and might not take place
spontaneously. In this respect, auditory training and/or speech-hearing
therapy may help hearing impaired people to derive maximum benefit from
sound amplification.
We believe the reassessment with auditory evoked potentials may have
been carried out too early, which prevented the plasticity of the
patients’ auditory system to happen. We also speculate if latency could
be rapidly affected by amplification as waves amplitude were [20].
The differences we observed on the IOI-HA were more likely associated
with sound amplification, regardless of the technology level. This
suggests that for new users, a well-fitted hearing aid may be the main
factor that guides satisfaction.