Download Audiometric analysis of type and degree of hearing

Journal of Advanced Clinical & Research Insights (2015), 2, 189–192
ORIGINAL ARTICLE
Audiometric analysis of type and degree of hearing
impairment and its demographic correlation:
A retrospective study
Sumanth Kanjikar1, Anil Doddamani2, Rajkamal Malige1, Nagbhushan Reddy1
Department of ENT, Bidar Institute of Medical Sciences, Bidar, Karnataka, India, 2Department of ENT, Employees State Insurance Corporation Medical College,
Gulbarga, Karnataka, India
1
Keywords
Audiometry, conductive, demography,
hearing impairment, screening
Correspondence
Dr. Sumanth Kanjikar, Assistant Professor,
Department of ENT, BRIMS, Bidar, Karnataka,
India. e-mail: [email protected]
Received 27 July 2015;
Accepted 5 September 2015
doi: 10.15713/ins.jcri.76
Abstract
Background: This retrospective study was done to know the demographic characteristics
of patients suffering from hearing loss. The type and degree of hearing impairment were
correlated with the demographic characteristics.
Aims and Objectives: (1) To establish the type and degree of hearing loss in patients
(2) evaluate age and gender-wise differences with respect to type and degree of hearing
loss. (3) Correlate age of a patient with degree of hearing impairment.
Materials and Methods: Audiometric data of 252 patients were taken. Demographic
characteristics were compared with types and degrees of hearing impairment.
Results: Sensorineural hearing loss (SNHL) type was the highest with 163 (66.5%)
out of 252 cases. Males were more affected by SNHL, mixed and conductive types. In
the SNHL category, the highest number of cases belonged to the 51-60 yeas age group
(24.5%) whereas in the conductive and mixed types of hearing loss, the maximum
patients were found in the 21-30 age group (51.5% and 25.6% respectively). Least
number of cases was in the age groups of 1-10 years followed by 81-90 years. Bilateral
impairment was more than unilateral impairment.
Conclusion: Our study concludes that men are more affected than women, bilateral
involvement is more common than unilateral, and SNHL type is the most common type
of hearing impairment.
Introduction
Hearing impairment is one of the most prevalent chronic
conditions after hypertension and arthritis.[1] Over 5% of the
world’s population - 360 million people - has disabling hearing
loss (328 million adults and 32 million children).[2]
The prevalence of hearing impairment is increasing with
increase in the ageing population and exposure to noise,
both occupational and at leisure. Hearing loss can impair the
communication skills of the affected person. The individual thus
suffers both physically and socially. In relation to public health,
hearing impairment is known to be associated with depression,
diabetes and dementia.[1] Approximately, one-third of people
over 65 years of age are affected by disabling hearing loss. The
prevalence in this age group is greatest in South Asia, Asia Pacific
and sub-Saharan Africa.[2] There are only a few audiometry based
studies about the demographic characteristics of patients with
hearing impairment. This hospital-based retrospective study
was done to know the demographic characteristics of patients
suffering from hearing loss. There was an attempt to correlate the
type and degree of hearing impairment with the demographic
characteristics.
Methods
This is a retrospective study on the audiometric data of
252 patients in the year 2013, who visited the outpatient
Department of Otolaryngology of Bidar Institute of Medical
Sciences, with different types and degrees of hearing impairment.
The data were compiled and groups based on demographic
characteristics such as age, [Graph 1] and sex were compared
with types and degrees of hearing impairment. The age of the
patients in this study ranged between 1 and 90 years. The types
of hearing impairment were categorized as sensorineural hearing
Journal of Advanced Clinical & Research Insights ● Vol. 2:5 ● Sep-Oct 2015189
Kanjikar, et al.
Audiometric analysis
Table 1: Distribution of study participants based on the type of
hearing impairment
Type
SNHL
n (%)
163 (66.5)
Conductive
33 (13.5)
Mixed
39 (15.9)
Mixed+SNHL
5 (2)
Others
5 (2)
SNHL: Sensorineural hearing loss
Graph 1: Age group distribution (in %) of study participants
loss (SNHL), conductive, mixed, mixed + SNHL, and others
(conductive loss in one ear and mixed or SNHL in the other)
[Table 1].[3] In this study, we also considered unilaterality and
bilaterality of hearing impairment.[3] The degree of hearing
impairment was graded as mild (25-40 dB threshold), moderate
(41-55 dB threshold), moderately severe (56-70 dB threshold),
severe (71-90 threshold), and profound (>90 dB threshold).[4]
All the observations were tabulated and subjected to
statistical analysis using Chi-square test.
Results
Age group distribution graph when observed reveals that more
number of patients belonged to the 51-60 years age group
accounting for 21.8% of total cases, followed by 21-30 years age
group with 20.8%. Least percentage of cases belonged to the
1-10 years age group with 0.8% cases [Graph 1]. The average age
of the patients was 45.8 years.
Gender distribution showed that males were more affected
with 66.9% of total cases compared to females with 33.1% of
cases.
Among the type of hearing impairment, SNHL was seen
in 163 (66.5%) out of 252 cases followed by 39 (15.9%) cases
of mixed type. Conductive type of hearing loss was seen in
33 (13.5%) cases. The other types of hearing impairment were
contributing to 2% of cases [Table 1].
When we compared gender-wise distribution of various
types of hearing impairment using Chi-Square test, we observed
that SNHL, mixed and conductive types of hearing impairment
affected more males, i.e., 71.2%, 69.2% and 51.5%, respectively,
compared to females. This difference showed statistically
significant P = 0.04 [Table 2].
Age wise comparison of various types of hearing impairments
among the study participants showed that in the SNHL category,
the highest number of cases belonged to the 51-60 yeas age
group(24.5%) whereas in the conductive and mixed types of
hearing loss, the maximum patients were found in the 21-30 age
group (51.5% and 25.6% respectively). Least number of cases
was in the age groups of 1-10 years followed by 81-90 years.
This difference in age and type distribution showed significant
P = 0.006 [Table 3].
190
Table 2: Comparison of gender‑wise distribution of various types
of hearing impairment using Chi‑square test
SNHL
Sex (n (%))
Total
Chi‑square P value
n (%)
value
Males
Females
116 (71.2) 47 (28.8) 163 (100.0)
8.235
0.04*
Conductive
17 (51.5)
16 (48.5)
33 (100.0)
Mixed
27 (69.2)
12 (30.8)
39 (100.0)
4 (40.0)
6 (60.0)
10 (100.0)
Type
Others
Total
164 (66.9) 81 (33.1) 245 (100.0)
*Statistically significant, SNHL: Sensorineural hearing loss
In our study population, we also observed that bilateral
hearing loss accounted for 89.8% of total cases compared to
10.2% of unilateral cases. Bilateral involvement was observed
in high percentage of the population in all the types of hearing
impairment as shown in Table 4.
When the types of hearing loss were compared with degree
of loss we observed that 27.6% of SNHL, 54.5% of conductive
and 60.0% of mixed + SNHL type patients showed moderate
degree of loss, whereas 51.3% of mixed showed moderately
severe degree of loss. This when compared showed a statistically
significant difference with a P < 0.001 [Table 5].
Discussion
In our study, we found that the age distribution of hearing loss
patients showed two peaks in the 51-60 age group (21.8%)
followed by 21-30 age group (20.8%). This being a hospital based
retrospective study based on pure tone audiometry of patients
presenting to the outpatient department with hearing loss,
prevalence of hearing loss in the population and in the different
age groups cannot be commented on, but the distribution of
hearing loss in this study is a fair indication of the prevalence of
hearing loss in different age groups and both the sexes.
Different studies have shown that the prevalence of hearing
loss increased with age among all demographic groups.[5] In
our study, the first peak was seen in the 21-30 age group maybe
because of the higher incidence of noise exposure in the working
class population and smoking in this age group.[6-8] The 51-60
age group peak could be due to age-related pathophysiologic
changes in the cochlea.[9] The data collected by Agrawal et al.
in their survey of the American population also suggest that the
Journal of Advanced Clinical & Research Insights ● Vol. 2:5 ● Sep-Oct 2015
Kanjikar, et al.
Audiometric analysis
Table 3: Age wise comparison of various types of hearing impairments among the study participants using Chi‑square test
Type
71‑80
16 (9.8)
81‑90
7 (4.3)
Total
n (%)
Chi‑square
value
P value
61‑70
26 (16.0)
163 (100.0)
45.111
0.006*
2 (6.1)
1 (3.0)
0 (0.0)
0 (0.0)
33 (100.0)
5 (12.8)
6 (15.4)
5 (12.8)
1 (2.6)
0 (0.0)
39 (100.0)
1 (10.0)
4 (40.0)
1 (10.0)
1 (10.0)
0 (0.0)
10 (100.0)
27 (11.0)
52 (21.2)
33 (13.5)
18 (7.3)
7 (2.9)
245 (100.0)
SNHL
1‑10
2 (1.2)
11‑20
12 (7.4)
21‑30
23 (14.1)
Age (years) (n (%))
31‑40
41‑50
51‑60
18 (11.0) 19 (11.7) 40 (24.5)
Conductive
0 (0.0)
4 (12.1)
17 (51.5)
7 (21.2)
2 (6.1)
Mixed
0 (0.0)
6 (15.4)
10 (25.6)
6 (15.4)
Others
0 (0.0)
1 (10.0)
1 (10.0)
1 (10.0)
Total
2 (0.8)
23 (9.4)
51 (20.8)
32 (13.1)
*Statistically significant, SNHL: Sensorineural hearing loss
Table 4: Comparison of distribution of different types of hearing
impairments with respect to the affected sides
Type
SNHL
Side affected (n (%))
Total
Chi‑square P value
n (%)
value
Unilateral Bilateral
6 (3.7) 157 (96.3) 163 (100.0)
29.926
<0.001*
Conductive
7 (21.2)
26 (78.8)
33 (100.0)
Mixed
12 (30.8)
27 (69.2)
39 (100.0)
0 (0)
5 (100.0)
5 (100.0)
0 (0.0)
5 (100.0)
5 (100.0)
Mixed+SNHL
Others
Total
25 (10.2) 220 (89.8) 245 (100.0)
*Statistically significant, SNHL: Sensorineural hearing loss
prevalence of hearing loss is increasing among the younger age
groups (20-29 and 30-39). This correlates with the findings of
our study.[5]
Evidence from several studies suggests that age-related
hearing loss differs between men and women.[9,10] In our study,
66.9% of the participants were male and 33.1% were females.
When we compared gender-wise distribution of various types
of hearing impairment using Chi-square test, we observed that
SNHL, mixed and conductive types of hearing impairment
affected more males, i.e. 71.2%, 69.2% and 51.5%, respectively,
compared to females. This difference showed statistically
significant P value of 0.04. This suggests that male sex itself is a
risk factor for developing hearing loss. This correlates well with
other studies.[1] A study on Korean population by Hong et al.
suggests that being male was independently associated with highfrequency mild hearing impairment.[1] Agrawal et al. conclude
that a disproportionate burden of hearing loss is experienced
by male and white (and to a lesser extent Mexican American)
participants and is manifest in the third decade of life. Their
study also suggests that men generally had higher prevalence of
bilateral, unilateral, and high-frequency hearing loss across the
age range compared with women.[5] It is likely that men have
a tendency to experience more occupational noise exposure,
more likely to smoke and more prone for other risk factors like
smoking and hypertension.[7,8,11]
In our study, Bilateral hearing loss accounted for 89.8% of the
cases and Unilateral for 10.2% cases. In all types of hearing loss,
bilateral involvement was seen more than unilateral loss.
In the study by Agrawal et al. they reported that approximately
50% speech frequency hearing loss was unilateral and 50% was
bilateral.[5] Though we did not divide the patients into speech
frequency and high frequency hearing loss categories, we had
significantly more number of patients in the bilateral category.
More percentage of people in the bilateral category could be
due to the fact that patients with bilateral hearing loss are more
likely to come to the hospital seeking help. Unilateral loss may
go unnoticed or not considered significant by the patient.
Systemic causes like atherosclerosis or Diabetes mellitus are
more common which lead to bilateral loss rather than unilateral
loss.[12-16]
Among the type of hearing impairment, SNHL was seen
in 66.5% cases followed by mixed type (15.9%). Conductive
type of hearing loss was seen in 13.5% cases. Such a big
burden of sensorineural hearing loss cases maybe due to an
ageing population,[9] more occupational and recreational
noise exposure,[7] increasing hypertension,[11] and diabetes
incidence.[13,14]
Age wise comparison of various types of hearing impairments
among the study participants showed that in the SNHL category,
the highest number of cases belonged to the 51-60 yeas age group
(24.5%) whereas in the conductive and mixed types of hearing
loss, the maximum patients were found in the 21-30 age group
(51.5% and 25.6% respectively). Least number of cases was in
the age groups of 1-10 years followed by 81-90 years. This again
indicated the effect of age on hearing loss of the sensorineural
type and effect of occupational noise exposure and smoking in
the working class population (21-30 years). We feel that the
lesser number of cases in the 1-10 and 81-90 age groups is an
underestimate of the true burden of hearing loss in these age
groups, as these patients are less likely to visit the hospital for
hearing problems because of school in the 1-10 years category
and because of other physical disabilities in the older age group.
This reiterates the importance of audiometric screening of
school going children to detect early onset hearing loss and
manage it so that the academic and social performance of these
children does not suffer.
In our study, most of the patients across the spectrum of
the types of hearing loss presented to the hospital when their
hearing loss was either moderate degree (27.6% of SNHL, 54.5%
of conductive and 60.0% of mixed + SNHL type patients) or of
moderately severe degree (51.3% of mixed type). This indicated
that either the mild hearing loss is not noticed by most of the
patients because it does not cause them significant problems in
Journal of Advanced Clinical & Research Insights ● Vol. 2:5 ● Sep-Oct 2015191
Kanjikar, et al.
Audiometric analysis
Table 5: Comparison of distribution of different types of hearing impairments with respect to the degree of impairment
Type
Total
n (%)
Chi‑square
value
P value
Profound
32 (19.60)
163 (100.00)
55.181
<0.001*
0 (0.00)
0 (0.00)
33 (100.00)
20 (51.30)
4 (10.30)
2 (5.10)
39 (100.00)
1 (20.00)
0 (0.00)
0 (0.00)
5 (100.00)
Degree UB (n (%))
Mod‑severe
Severe
40 (24.50)
19 (11.70)
SNHL
Mild
27 (16.60)
Moderate
45 (27.60)
Conductive
13 (39.40)
18 (54.50)
2 (6.10)
Mixed
1 (2.60)
12 (30.80)
Mixed+SNHL
1 (20.00)
3 (60.00)
Others
2 (40.00)
0 (0.00)
2 (40.00)
0 (0.00)
1 (20.00)
5 (100.00)
Total
44 (18.00)
78 (31.80)
65 (26.50)
23 (9.40)
35 (14.30)
245 (100.00)
*Statistically significant, SNHL: Sensorineural hearing loss
their daily activities or there is a tendency to neglect mild hearing
loss. In India, many patients with age-related hearing loss don’t
seek medical help. Therefore, audiometric screening is necessary
in apparently healthy people to detect mild hearing loss so that
these persons can be helped by dealing with the correctable
causes, taking care of the risk factors and by giving them suitable
hearing aids. Agrawal et al. also suggested that audiometric
screening is critical to capture the true prevalence of hearing loss,
particularly at an early pathogenetic stage among young adults.[5]
Conclusion
It can be said in conclusion that hearing loss prevalence is
increasing globally because of the increase in life expectancy and
in the younger age group because of occupational and recreational
noise exposure and smoking. It is of utmost importance to detect
the mild hearing loss cases early by audiometric screening at the
school level for effective management of these cases. The general
population has to be made aware of the risk factors for hearing
loss like smoking, noise exposure. There is also a need for a crosssectional study in India to estimate the true prevalence of hearing
loss.
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How to cite this article: Kanjikar S, Doddamani A, Malige R,
Reddy N. Audiometric analysis of type and degree of hearing
impairment and its demographic correlation: A retrospective
study. J Adv Clin Res Insights 2015;2:189-192.
Journal of Advanced Clinical & Research Insights ● Vol. 2:5 ● Sep-Oct 2015