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Department of Clinical Science, Intervention and Technology ,

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 ,

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Department of Clinical Science, Intervention and Technology ,

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  1. 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, 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

  2. 1914 2004 1866 The Swedish Armed Forces have relied on a conscript system where all young men, liable for compulsory military service, constitute the fundament - recently also voluntary for women The conscript system is phased out in July 2010 after almost 200 years The conscript system was introduced in 1811

  3. All servicemen who are drafted undergo medical examinations, including screening audiometry at: 1) Conscription at age 18 years 2) 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

  4. Prevalence values of mild – moderate hearing loss in six age cohorts of 18-year old men from 1971 to 1995 Numbers of participants in the study (n: 301 873) and participation rate

  5. 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 • 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

  6.    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

  7. 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

  8. Hearing in young men – The influence of military noise exposure Two groups of conscripts studied 1999 – 2000, and 2002 - 2005 Design: prospective, longitudinal and cross-sectional studies n: 1724

  9. 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 decline compared to those with normal hearing 747 servicemen, aged 20 - 24 years, studied 1999 - 2000 291 military engineers, 252 infantry men, 204 artillery men Subgroup: 95 conscripts (12.7%) who had a mild hearing loss at reporting for training Comparison group: 138 men followed from the conscription to reporting for training

  10. Incidence of significant threshold shift (STS), risk ratio (RR) and 95% confidence interval (CI) relative the comparison group

  11. Incidence of STS, risk ratio (RR) and 95% confidence interval (CI) relative the comparison group and military servicemen with different noise exposure

  12. Incidence of STS, RR and CI among the conscripts with and without a mild hearing loss at reporting for training relative the comparison group.

  13. Conclusions 1. Hearing in young men – The influence of military noise exposure 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 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 The study resulted in stricter military safety rules in 2000

  14. 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

  15. 2. Hearing in young men The influence of military noise exposure Self-assessed auditory symptoms (per cent) Prevalence values (often always) Hearing impairment <20 dB HL (per cent) Prevalence values

  16. 2. Hearing in young men – The influence of military noise exposure • 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 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

  17. 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 training Improvements of the Hearing Conservation Program for the Swedish Armed Forces, now with professional personnel, aresuggested

  18. Research group P Muhr U Rosenhall PA Hellstrom B Mansson B Hagerman F Rasmussen

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