VOLUME 10 NUMBER 4 • NOVEMBER 2013
131
SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
as the values are close to 6 dB, the minimum limit for normal
DPOAE measurements.
Relationship between auditory function in individuals with
T1DM and duration of T1DM
Fig. 4 indicates that the PTA was highest for an individual with
a 20-year duration of T1DM. However, the PTA decreased for
individuals who had had TIDM for 21 years and longer. The Pearson
correlation coefficient was 0.047. This statistical value had no
significance but this may have been due to the small sample size of
the current study.
Discussion
According to the research literature, auditory function has been
reported in individuals with T1DM, using a combination of
audiometric testing procedures such as pure-tone audiometry,
tympanometry, OAEs and ABRs.
11,13,14,28-31
The results from the
auditory characteristics in individuals diagnosed with T1DM in
Gauteng, South Africa, are discussed in accordance with the sub-
aims of the study.
On examination of prevalence of cochleovestibular symptoms
such as tinnitus and vertigo in T1DM, the current results indicated
that vertigo was most prevalent (56%), with tinnitus presenting
in 11% of the sample. This is consistent with the literature, which
suggests that individuals with T1DM may have cochleovestibular
symptoms such as tinnitus and vertigo,
8, 32,33
and tinnitus has been
found to precede hearing loss.
14
The current findings have implications for audiologists who
should be cognisant of these cochleovestibular symptoms when
assessing and managing individuals diagnosed with T1DM. Vertigo
can have detrimental effects in an individual if not treated in terms
of propensity to falls; and both vertigo and tinnitus can have a
serious and negative impact on quality of life. Probing for these
symptoms during routine medical follow up of individuals with
T1DM can ensure early identification and intervention.
With regard to the description of the results of the basic
audiological assessment of individuals diagnosed with T1DM and
the controls, otoscopic examination in both groups indicated
normal middle ear function bilaterally. The findings from impedance
audiometry indicated no differences between the control and
experimental groups, suggesting that T1DMdoes not have anegative
effect on impedance audiometry. These findings are consistent
with published data,
30
which concluded that individuals with T1DM
have normal impedance audiometry. Pathophysiologically, it can
be argued that middle ear function would not be expected to be
impacted on by T1DM.
The results of the pure-tone audiometry indicated no statistically
significant difference between the experimental and control group
data. Furthermore, none of the individuals with T1DM had a clinical
hearing loss based on the PTA (i.e. all PTAs were below 26 dB).
However the mean auditory threshold of each frequency in the
right and left ear and the PTA value in both ears were higher at
all frequencies in the experimental group, compared to those in
the control group. This was more clearly noted at 6 000 Hz for
both ears and was noteworthy at 8 000 Hz as well. These findings
indicate that individuals with T1DM have auditory thresholds that
are higher than those without T1DM. This finding is supported by
Ferrer
et al.
29
and Pessin
et al.
14
In addition, the elevated thresholds at 6 000 and 8 000 Hz may
be an indication of progression of a possible high-frequency hearing
loss. This is characteristic of T1DM, which affects predominantly the
higher frequencies.
31
It is crucial that audiologists in South Africa
are mindful that individuals with T1DM have elevated thresholds in
the high frequencies, specifically 6 000 and 8 000 Hz.
The mild degree of clinical audiological changes in the current
sample could have been a feature of T1DM or it may have been
influenced by the younger age range of the participants as well as
the small sample size. Nonetheless, the findings indicate a need
for more in-depth research in this group with a wider range of
participants who have had T1DM for a longer period of time.
Speech audiometry results also indicated no statistically
significant difference between the experimental and control group
data. This finding is the same as that by Parving
et al.
32
who also
found no significant difference between individuals with T1DM
and healthy individuals and their corresponding mean values for
SRT and SD. However, the mean SRT and SD speech level values
were again found to be elevated in the experimental group. This
is consistent with the elevated pure-tone audiometry results in
the T1DM group. Impaired speech audiometry findings have a
significant impact on quality of life of the impaired individual as
Fig. 4.
Duration of T1DM in years versus PTA.
Fig. 3.
Mean values of left and right ear DPOAEs and pure tones.
