Department of Clinical Science, Intervention and Technology, Karolinska Institutet, and the Department of Audiology, Karolinska University Hospital, Stockholm, Sweden The Swedish Armed Forces, The Occupational Health Center at the Garrison of Halmstad, Sweden valence values of hearing impairment and self-asses uditory symptoms among young Swedish men, 1971 - 20 Per Muhr, Ulf Rosenhall Presenter: Ulf Rosenhall, MD, PhD
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Prevalence values of hearing impairment and self-assessed auditory symptoms among young Swedish men, 1971 - 2005. Per Muhr, Ulf Rosenhall. Presenter: Ulf Rosenhall , MD, PhD. Department of Clinical Science, Intervention and Technology , - PowerPoint PPT Presentation
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Department of Clinical Science, Intervention and Technology, Karolinska Institutet, and the Department of Audiology,
Karolinska University Hospital, Stockholm, SwedenThe Swedish Armed Forces, The Occupational Health
Center at the Garrison of Halmstad, Sweden
Prevalence values of hearing impairment and self-assessed auditory symptoms among young Swedish men, 1971 - 2005
The Swedish Armed Forces have relied on a conscript system where allyoung men, liable for compulsory military service, constitute the
fundament - recently also voluntary for women
The conscript systemwas introduced in 1811
The conscript system isphased out in July 2010after almost 200 years
1866
1914
2004
All servicemen who are drafted undergo medical examinations, including screening audiometry at:
1) Conscription at age 18 years2) Reporting to service at 18 – 22 years of age 3) Discharge after 260 days of military service 4) Any occasion during military service, if indicated
All medical data are filed and available to research after ethical approval
There is a possibility to add questionnaires for quality assurance
Numbers of participants in the study (n: 301 873) and participation rate
Prevalence values of mild – moderate hearing loss in six age cohorts of 18-year old men from 1971 to 1995
Prevalence of hearing loss at discrete frequencies (0.5 to 6 kHz), in the total material 1971 - 1995. Threshold elevations 25 – 30 dB
HL, 35 – 40 dB HL, and ≥45 dB HL. Left ear
A, Left ear
0
1
2
34
5
6
7
8
0,5 1 2 3 4 6
Frequency
Pre
vale
nce
, %
>=45 dB
35 - 40 dB
25 - 30 dB
Prevalence values of threshold elevations
• 13.1 % All threshold• 11.9 % High frequency
threshold• 3.2 % Bilateral high
frequency thresholds
• 7.5 % Left ear• 6.2 % Right ear
0
2
4
6
8
10
Per
cen
t
1971 1976 1981 1986 1991 1995
Year of Conscription
LEFT EAR
0
2
4
6
8
10
1971 1976 1981 1986 1991 1995
Year of Conscription
0.5kHz
1kHz
2kHz
3kHz
4kHz
6kHz
RIGHT EAR
Development of hearing loss at discrete frequencies in 18-year old men from 1971 to 1995
High frequency hearing loss decreased from 15.3 % in 1971 to 8.3 % in 1981, and increased to 14.3 % in 1995 above all at 6 kHz
0
2
4
6
8
10
12
14
16
18
1971 1976 1981 1986 1991 1994
Year
Pre
vale
nce
% >= 45 dB HL
35-40 dB HL
25-30 dB HL
Prevalence of at least one threshold 25 dB HL in one or both ears at 3, 4 or 6 kHz, %
>40 dB HL the prevalence decreased from 3.8% in 1971 to 1.9% in 1995
Peak level156 dB SPL
103-107 dB(A)
Peak level 175-184 dB SPL
Hearing in young men – The influence of military noise exposure
Two groups of conscriptsstudied 1999 – 2000, and 2002 - 2005Design: prospective, longitudinal and
cross-sectional studies n: 1724
1. Hearing in young men – The influence of military noise exposure
• To investigate the incidence and the relative risk of hearing deterioration during primary military service among military servicemen with different noise exposure
• To investigate if those of the conscripts who had a mild hearing loss when reporting for training had an increased risk of hearing
Incidence of STS, RR and CI among the conscripts with and without a mild hearing loss at reporting for
training relative the comparison group.
Hearing thresholds at
reporting
Total
number
Incidence of
STS, number
Incidence of
STS, %
RR CI, 95 %
Comparison group 138 4 2.9
All freq. 20 dB HL or
better
652 43 6.6 2.2 0.8 – 6.0
At least one freq. >20
dB HL
95 16 17 6.8 2.1-29
There still occurs hearing deterioration above all in the artillery in spite of the military hearing preservation program
Those of the conscripts who already at reporting for training had a mild hearing loss seemed to be at higher risk
Hearing decline: Controls: 2.9%; Military servicemen: 7.9%Conscripts with HI at reporting to service: 17% From 2.3% to 23.2% related to military noise exposure
The study resulted in stricter military safety rules in 2000
Conclusions1. Hearing in young men – The influence of military
noise exposure
2. Hearing in young men – The influence of military noise exposure
• To estimate prevalence and incidence values of and relations between auditory symptoms, slight hearing loss, and noise exposure before and during primary military service
• To study prognostic values of tinnitus and ototraumatic indicators on auditory deterioration during military service
• To study knowledge, attitude to and efficacy of the present Hearing Conservation Program in the Swedish Armed Forces
839 servicemen, aged 19 - 22 years, studied longitudinally 2002 – 2005 at reporting to training and at the end of the service. Length of military service: 260 days (7.5 - 11 months)
Military units: Anti-aircraft regiment; Artillery regiment; Armoured regiment
Methods: screening audiometry and questionnaires
Reporting Discharge
Hearing problems 20.7 (1.7) 28.4 (3.3)
Hearing probl. in noise 35.7 (2.3) 37.6 (4.8)
Tinnitus 23.2 (3.4) 31.9 (4.8)
Sensitive to noise 15.5 (1.9) 18.9 (2.2)
Conscription Reporting Discharge
0.5 – 8 kHz 6.3 14.5 24
3, 4, 6 kHz 2.6 7.4 12.3
8 kHz 3.5 9.8 14.8
Hearing impairment<20 dB HL(per cent)Prevalence values
• High prevalence values of self-assessed problems and of noise exposure
• Risk factors for tinnitus: Tinnitus/TTS after noise exposure; Active music performance; Frequent otitis media in childhood; History of concussion and loss of consciousness
• Elevated incidence of hearing decline during military service, especially for those who reported acoustic accidents
• Auditory symptoms and hearing loss are common at reporting among the group (4%) who interrupted the training because of hearing problems
2. Hearing in young men – The influence of military noise exposure
The risk of hearing decline during military service has decreased (RR: 2.7 in the late 90:ies to 1.8) but has not been eliminated
Conclusions and Summary
Audiometric data collected by the Swedish Armed Forces during the last 40 years have been used to study the epidemiology of mild - moderate hearing loss in young men
Long-term fluctuations of prevalence values of pure tone threshold elevations have been demonstrated, with increasing prevalence of high frequency hearing loss to the mid 90:ies
Military service implies a risk for hearing impairment and auditory symptoms (e.g. tinnitus). The risk is related to the noise levels during military trainingImprovements of the Hearing Conservation Program for the Swedish Armed Forces, now with professional personnel, are suggested
Research group
P MuhrU RosenhallPA HellstromB ManssonB HagermanF Rasmussen