VOLUME 10 NUMBER 4 • NOVEMBER 2013
129
SA JOURNAL OF DIABETES & VASCULAR DISEASE
RESEARCH ARTICLE
Distortion product otoacoustic emissions (DPOAEs):
DPOAEs for the
current study were evaluated on the Capella Madsen diagnostic
machine, as it can measure the response of the cochlear amplifier in
discrete frequency ranges. The stimulus parameters that were used
for DPOAEs are as follows: intensity (L1 = 65 dB SPL, L2 = 55 dB
SPL), ratio (f2/f1 = 1.22) and frequency range (500–8 000 Hz). To be
considered a valid DPOAE, the DP amplitude had to exceed the noise
floor value by at least 6 dB and fall within the normative region.
22
Statistical analysis
For data management and analysis, qualitative and quantitative
statistical analysis of the results was performed. Descriptive statistics
were used to describe socio-demographic characteristics of the
sample and to evaluate whether DPOAE tests are more sensitive
in detecting the early signs of cochlear dysfunction than the basic
pure-tone test battery.
23
Fisher’s exact test was used to determine the prevalence of
cochleovestibular symptoms in order to test the significance of any
association of difference between two independent samples.
24
The
independent-samples
t
-test helped assess the results of the basic
audiological assessment and the DPOAE, assessing the significant
difference between the means of two groups on the dependent
variable.
25
Pearson’s correlation coefficient was used to determine
the relationship between the auditory function in individuals with
T1DM and age of onset, as it measures the degree of relationship
between two variables and allows making predictions from one
variable to another.
26
Results
As indicated in Table 1, the experimental group consisted of nine
individuals (two males and seven females) who were medically
diagnosed with T1DM. The control group consisted of nine
individuals (two males and seven females) without T1DM and with
no known hearing loss. The age of the participants ranged between
19 and 40 years. The mean age for the experimental group was
26.5 years (standard deviation = 6.54) and the mean age for the
control group was 26.2 years (standard deviation = 4.65).
Prevalence of cochleovestibular symptoms such as tinnitus
and vertigo in T1DM
The statistical results from the Fisher’s exact test conducted
indicated no relationship between the cochleovestibular symptoms
and T1DM. The corresponding
p
-value, if below 0.5, indicated a
relationship between T1DM and the cochleovestibular symptoms.
However descriptively (as depicted in Table 2), vertigo was most
prevalent in the experimental group (56%), with tinnitus at 11%.
Results of basic audiological assessment for T1DM individuals
and controls
The otoscopic examination for the experimental and control group
was clear. This means that no obstruction was present and normal
tympanic membranes were clearly visible in all participants. No
differences were noted between the groups.
Impedance audiometry
Tympanometry:
the
p
-value for the middle ear static compliance, ear
canal volume and middle ear pressure are indicated in Table 3. There
were no significant differences in the scores for the experimental and
control group.
Acoustic reflexes:
an independent samples
t
-test was conducted to
compare the acoustic reflexes at each frequency, bilaterally in both
groups. The
p
-values for the acoustic reflexes at each frequency
are presented in Table 3. There were no statistically significant
differences in the scores for the experimental and control groups.
These results suggest that T1DM does not have a statistically
significant effect on acoustic reflexes.
Pure-tone audiometry:
an independent samples
t
-test was
conducted to compare the intensity values at each frequency in
the experimental and control groups. The
p
-value for the intensity
values at each frequency is shown in Table 3. Again, there were no
statistically significant differences in the scores for the experimental
and control groups. These results suggest that T1DM did not have
an effect on pure-tone audiometry in the current sample.
Fig. 1 illustrates the mean values of right and left ear pure tones,
and mean pure-tone average values for both groups, respectively.
Visual descriptive analysis of the data illustrates that although
the mean values for the right and left ear pure tones were within
normal limits for the experimental group, they were higher than
those of the control group. The greatest difference was noted at
6 000 Hz.
Speech audiometry
There was no statistically significant difference for SRT values
(
p
= 0) and SD values (
p
= 0.7) in the experimental and control groups
when the independent samples
t
-test was conducted. These results
suggest that T1DM did not have a statistically significant effect on
SRT or SD. However, descriptively, mean SRT and SD values were
higher in the experimental group compared to the control group.
For the experimental group: SRT (RE) = 12.22 dB HL, SRT (LE) =
10 dB HL; SD (RE) = 98 dB HL, SD (LE) = 97 dB HL. For the control
group: SRT (RE) = 5 dB HL, SRT (LE) = 5 dB HL; SD (RE) = 95 dB HL,
SD (LE) = 96 dB HL.
Table 1.
Demographic profile of the participants
.
Factor
Group 1
(19–25 years)
Group 2
(26–31 years)
Group 3
(32–40 years)
Exp Control
Exp Control
Exp Control
Number of
participants
4
4
3
3
2
2
Age (mean)
21 21
27.3 28.3
36.5 33.5
Males/females
1/3 0/4
0/3 1/2
1/1 1/1
Table 2.
Prevalence of cochleovestibular symptoms for the experimental and
control groups.
Factor
Tinnitus
Vertigo
Yes No
Yes No
Experimental
1
8
5
4
Control
1
8
0
9
p-value
9
undefined
