Assessment of hearing loss among taxi and agency drivers
in a city in northern Iran in 2011
Beheshti MH, MSc1, Firoozi chahak A,
MSc1*, Alinaghi Langari
AA, MSc2
1-
Faculty Member, Dept. of Occupational Health, Faculty of Health, Gonabad University of Medical Sciences, Gonabad,
Iran. 2- Faculty Member, Dept. of Occupational Health, Faculty of Health, Bam University of
Medical Sciences, Bam, Iran.
Abstract Received:
January 2016,
Accepted: April 2016
|
Background: Taxi drivers have the most
important role in the public transport services. They are exposed to various
harmful agents and occupational hazards. Noise is a harmful occupational
factors and hearing loss is its most important effect. Protection of drivers
against hearing loss is essential.
This study was performed to determine the
prevalence of hearing loss among taxi and agency drivers. Materials and Methods: This cross-sectional study was performed on 95 drivers (43 taxi
drivers and 52 agency drivers)
who were selected via simple random sampling. The
threshold of drivers' hearing was measured by an audiometer. After data
extraction, data were analyzed using Kruskal-Wallis test to compare the
average level of hearing between the left and right ears and drivers. Results: The average age of taxi drivers and agency drivers was 43.5 ±
10.8 and 40.7 ± 8.3 years,
respectively. In addition, the average work experience of
taxi drivers and agency drivers was 9.5 and 6.5 years, respectively. The
average of hearing threshold level in right and left ears of agency drivers
was 12.96 ± 4.2 and 12.74 ± 4.64 dB and of taxi drivers was 12.53 ± 5.16 and
15.61 ± 12.7 dB, respectively.
A hearing threshold of less than 25 dB in each
ear illustrates the lack of hearing loss; thus, the studied drivers did not
have hearing loss. Conclusions: The results showed that the
drivers hearing status was satisfactory.
Furthermore, the prevalence of hearing
loss in taxi drivers was higher than agency drivers. |
Keywords: Hearing loss, Noise-induced
hearing loss, Noise, Drivers, Audiometry.
Introduction
Noise is irregular and unwanted sound waves that generally exposure to them
is inevitable (1(. Noise is one of the factors threatening
the health of workers in different occupations such as taxi driving. Sound can have significant
effects on humans from different aspects. In addition, it can lead to hearing
impairments and physiological effects such as increased blood pressure and
heart rate, impact on visual organs and the human balance control system, psychiatric
and neurological effects, sleep disorders, subjective
effects, interference in communication, and social problems (2-8). Noise in the work environment
can affect individuals' safety and efficacy, and thus, may lead to accidents in
the workplace. Communication problems, failure to maintain alertness and concentration,
and stress and fatigue increase in individuals who are exposed to noise (9-12). Hearing loss is the most
important noise-induced disorder, although noise-induced hearing loss is preventable. However, it is now considered
as a major health problem and one of the* 10 most
common occupational diseases, and thus, as one of the most important
occupational diseases in Europe (13, 14).
The World Health Organization (WHO) has estimated the daily amount of
financial losses caused by noise as nearly 4 million dollars (15).In 1992, it
was estimated that approximately 1.7 million people in the UK were experiencing
hearing loss (16). According to
the WHO, noise pollution is considered as the third harmful factor in large
cities. Although noise pollution in urban areas is caused by a variety of
sources such as road traffic, construction, businesses, airports, and
industrial and residential areas (7, 17),
vehicle traffic is the most important factor in the development of urban
noise (18). This problem
is intensified by the increase in vehicles in urban networks (19). Automobiles are considered as
moving environmental sources of noise (traffic) and also occupational sources
of noise for drivers (17).
Driving is one of the occupations that expose individuals to physical and
psychological stressors such as noise, vibration, oscillation, and ergonomic
problems and safety risks such as accidents (20, 21). Drivers are exposed to high
levels of noise due to working with old and faulty vehicles, on very bumpy
roads, and dealing with different people during their work shift (22).Many
studies have been conducted in industrial environments in relation to
occupational hearing loss; however, very few studies have been performed on
hearing loss in taxi drivers.
The study conducted by Lewis et al. on drivers showed that the threshold of
hearing in 22% of drivers was high at frequencies ranging from 3000 to 6000 Hz
and its value increased with age (23).
Berjis et al. in their study on drivers of heavy vehicles,
showed that hearing thresholds at 2000 Hz in the left ears of subjects were
significantly higher than the right ears (24). In many studies, the prevalence of hearing loss among
drivers has been reported as 32.6% to 55.4% (25,26). This study aimed to determine
the prevalence of hearing loss among taxi drivers in a city in northern Iran.
Material and Methods
In this cross-sectional study that was conducted in 2011, the hearing of 95
drivers in a northern city of Iran was evaluated. The participants were divided
into two groups of taxi drivers (n = 43) and agency drivers (n = 52). The number of subjects was determined
according to the formula for determination of sample size in descriptive
studies (Equation 1).
The subjects were selected randomly.
The inclusion and exclusion criteria of this study consisted of 1 year work
experience, lack of neurological and hearing disorders, willingness to
participate in the study, and lack of a second job.
It should be noted that confounding factors, such as history of ear
disease, history of working in noisy work environments and risk of hearing loss
caused by it, use of certain drugs such as streptomycin and gentamicin, a blow
to the head, and etcetera that affect the hearing, were excluded from the
study. After
recording the demographic data of drivers, an audiometer (MAICO, Minneapolis,
MN, USA) was used to assess the status of their hearing. The audiometry
test was performed in an acoustic room. The hearing thresholds of drivers were
measured separately for left and right ears at frequencies of 250, 500, 1000,
2000, 4000, and 8000 Hz and were recorded on audiogram sheets. In the next step, the average
of the hearing thresholds was calculated per person at frequencies of 500 to
4000 Hz for each ear.
In this study, all data were analyzed in SPSS software (version 17, SPSS
Inc., Chicago, IL, USA). In addition, Kruskal-Wallis test was used to compare
the average level of hearing between left and right ears and drivers.
Results
The demographic information of these subjects is presented in tables 1 and
2. Mean age of all drivers was 41.9 ± 9.6. Mean age of taxi
and agency drivers was 43.5 ± 10.8 and 40.7 ± 8.3, respectively.
Table 1: The age
range of studied taxi and agency drivers (n = 95)
|
Agency drivers |
Taxi drivers |
Age group |
|
Number (%) |
Number (%) |
|
|
6 (11.5) |
5 (11.6) |
Less than 30 years |
|
13 (25) |
10 (23.3) |
30 to 40 years |
|
26 (50) |
16 (37.2) |
40 to 50 years |
|
7 (13.5) |
12 (27.9) |
More than 50 years |
According to the results of this study, mean work experience of drivers was
7.9 ± 3.4 years, and maximum and minimum work experience of drivers was 22
years and 1 year, respectively.
The range of work experience of the studied taxi and agency drivers is shown
in table 2.
Table 2: The work
experience range of the studied taxi and agency drivers
|
Work experience (years) |
Agency drivers |
Taxi drivers |
|
Number (%) |
Number (%) |
|
|
Less than 5 |
22 (42.3) |
17 (39.5) |
|
5 to 10 |
19 (36.5) |
14 (32.6) |
|
10 to 15 |
4 (7.7) |
3 (7) |
|
15 to 20 |
3 (5.8) |
1 (2.3) |
|
More than 20 |
4 (7.7) |
8 (18.6) |
Mean hearing threshold level (at 500 to 4000 Hz) for right and left ears of
agency drivers was 12.96 ± 4.2 and 12.74 ± 4.64 dB and taxi drivers was 12.53 ±
5.16 and 15.61 ± 12.7 dB, respectively.
Mean hearing loss in the two groups of drivers, according to
sound-frequency, is shown in table 3 and figure 1.
Figure 1:
Mean hearing loss according to sound-frequency
among taxi and agency drivers
Table 3: Overall
hearing loss in taxi and agency drivers
|
Group |
Ear |
Hearing loss |
Overall hearing
loss |
|
Agency drivers |
Right |
12.96 ±
4.4 |
13.42 ± 4.2 |
|
Left |
12.74 ±
4.64 |
||
|
Taxi drivers |
Right |
12.53 ±
5.16 |
14.6 ± 8.17 |
|
Left |
15.61 ±
12.7 |
In this study, 77.5% of
agency drivers and 6.98% of taxi drivers had partial hearing loss. Overall hearing loss in taxi
and agency drivers is shown in table 3.
According to table 3, the incidence of hearing loss was higher in taxi
drivers than agency drivers.
Kruskal-Wallis test results showed no significant difference between the
two groups in terms of hearing loss (P > 0.050). Spearman’s correlation
coefficient showed that in agency drivers and taxi drivers there was a
significant relationship between hearing loss and age with correlation
coefficients of 0.497 and 0.666, respectively, (P < 0.001). There was a significant
correlation (r = 0.485) between hearing loss and work experience in taxi
drivers (P ý<ý 0.001). However, no
significant correlation was observed between hearing loss and work experience
in agency drivers (P > 0.050).
According to the Kruskal-Wallis test results, there was no significant
difference in the mean threshold of hearing of right and left ears between the
two groups (Pleft = 0.920) (Pright = 0.280).
Discussion
The results of this study indicated that the drivers’ hearing status was
satisfactory. This may be due to lack of traffic on roads and streets and lack
of noise-producing resources in their city. The low work experience of drivers
may also be the cause of this result. The study by Pourabdian et al. showed
that the prevalence of bilateral noise-induced hearing loss in drivers in
Isfahan, Iran, was 18.1% (27). The prevalence rates were higher in the left ear
(6.5%) than the right ear (3.0%) (27).
The results of the present study showed that hearing loss or, in other
words, average hearing threshold level in taxi drivers was higher than agency
drivers. One reason
for this could be that taxi drivers drive throughout their work shift and
circulate in the streets. Nevertheless, agency drivers only drive and are
exposed to noise when they have passengers and stop at the agency when they do
not. As shown in
many studies, average of hearing threshold at 4000 Hz in the left and right ear
of drivers is greater than other frequencies, which confirms occupational
hearing loss (28, 29).
The results of this study show that the hearing threshold of agency drivers
in the right ear was higher than the left ear. This finding is not in agreement
with the results of the study by Berjis et al. (24). Lopes et al. in their study
showed that hearing loss is significantly associated with age and work
experience of drivers (23), which is in contradiction with the results of this
study. Many studies
(30,31)have shown that hearing loss affects health and
quality of life (QOL) and the prevalence of hearing loss may be growing because
of an aging population and increasing noise exposure. The study by Agrawal
showed that in 2003-2004, 16.1% of US adults (29 million Americans) had voice
frequency hearing loss (30). In the youngest age group (20-29 years), 8.5%
exhibited hearing loss, and the prevalence seemed to be growing among this age
group. The odds of
hearing loss were 5.5 times higher in men compared to women and 70% lower in
black subjects compared to white subjects. Increases in hearing loss prevalence
occurred earlier among participants who smoked, were exposed to noise and at
risk of cardiovascular diseases (30). The study by Shargorodsky also showed
that the prevalence of any hearing loss in adolescents in the US increased
significantly from 14.9% in 1988-1994 to 19.5% in 2005-2006 (31). Thus, the prevalence of hearing
loss among a sample of adolescents in the US aged 12 to 19 years was higher in
2005-2006 compared with 1988-1994 (31).
Effective factors in differentiating between the results of studies are
driving type (urban or suburban) and vehicle type (light or heavy vehicle). Other effective factors in
desirability of Hearing status of drivers investigated in this study can be
their work experience,
because work experience of 42.2% of agency drivers and 39.5% of taxi
drivers was less than 5 years that included more than a third of the drivers. However, based on the results of
this study, taxi drivers did not have noise-induced hearing loss. Nevertheless,
human exposure to noise can lead to effects and complications such as
temporary and permanent hearing loss, neurological and psychiatric disorders,
reduced efficiency, and increased hazards (32, 33). Furthermore, noise has
indirect effects on human performance including efficiency and productivity
reduction, and increased risk of accidents due to lower focus (34).
Therefore, you must first apply the sound control on the devices that produce a
lot of noise.
Conclusion
According to results of this study, the average of
hearing threshold level in right and left ears of agency drivers was less than
25 dB and the studied drivers did not have hearing loss.
Acknowledge
We would like to thank the drivers who participated in this project and
helped us in performing this project.
Conflict of
interests: None declared.
References
1.
Golmohammadi
R. Noise and vibration engineering. 3rd ed. Hamadan: Daneshjo Press;
2007.
4.
Berrien
FK. The effects of noise. Psychol Bull 1946; 43(2):141-61.
10.
Hétu
R, Quoc HT. Psychoacoustic performance in workers with PAIR. In: Axelsson A, Borchgrevink H, Hamernik RP,
Hellstrom P, Henderson D, Salvi RJ, editors. Scientific basis of noise-induced
hearing loss. New York: Thieme; 1996. P.264-85.
13.
Monson
RR. Occupational epidemiology. 2nd ed. Boca Raton, FL: CRC Press;
1990.
16.
Godlee
F. Noise: breaking the silence. BMJ 1992; 304(6819):110-3.
19.
Ouis
D. Annoyance from road traffic noise: a review. J Environ Psychol 2001;
21(1):101-20.
24.
Berjis
N, Soheilipoor S, Poorabdian S, Akbari S. Evaluating the Relative Frequency
or Hearing Loss on Heavy Vehicles Derivers. Journal of Isfahan Medical School
2011; 28(120):1-6.
26.
Barbosa AS,
Cardoso MR. Hearing loss among workers exposed to road traffic noise in the
city of São Paulo in Brazil. Auris Nasus Larynx 2005; 32(1):17-21.
27.
Janghorbani M,
Sheikhi A,
Pourabdian S. The prevalence and correlates of hearing loss in drivers in
Isfahan, Iran. Arch Iran Med 2009; 12(2):128-34.
28.
Brant LJ,
Gordon-Salant S, Pearson JD, Klein LL, Morrell CH, Metter EJ, et al. Risk
factors related to age-associated hearing loss in the speech frequencies. J Am
Acad Audiol 1996; 7(3):152-60.
29.
Weisz N, Hartmann
T, Dohrmann K, Schlee W, Norena A. High-frequency tinnitus without hearing loss
does not mean absence of deafferentation. Hear Res 2006; 222(1-2):108-14.
30.
Agrawal Y, Platz
EA, Niparko JK. Prevalence of hearing loss and differences by demographic
characteristics among US adults: data from the National Health and Nutrition
Examination Survey, 1999-2004. Arch Intern Med 2008; 168(14):1522-30.
31.
Shargorodsky J,
Curhan SG, Curhan GC, Eavey R. Change in prevalence of hearing loss in US
adolescents. JAMA 2010; 304(7):772-8.
32.
Crocker MJ,
Ivanov IN. Noise and vibration control in vehicles. 1st ed.
Petersburg, Russia: Interpublish Ltd; 1993.
33.
Zulkarnain RZ,
Nor MJM. Noise control using coconut coir fiber sound absorber with porous
layer backing and perforated panel. Am J Appl Sci 2010; 7(2):260-4.
34.
Saeki T, Fujii T,
Yamaguchi S, Harima S. Effects of acoustical noise on annoyance, performance
and fatigue during mental memory task. Appl Acoust 2004; 65(9):913-21.
* Corresponding author: Ali Firoozi chahak,
Dept. of Occupational Health, Faculty of Health, Gonabad
University of Medical Sciences, Gonabad, Iran.
Email: ali_firoozi66@yahoo.com