A Modern Approach to Noise-Induced Hearing Loss from Military Operations

9 December 2009

'A Modern Approach to Noise-Induced Hearing Loss from Military Operations' brought together interested parties from the armed forces, the NHS, academic research and the voluntary sector to share and update knowledge of the science relevant to noise induced hearing loss and the practical problems faced during military operations.

Abstracts for each presentation are given below, together with a link to download the presentation, where available.

Abstracts

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Noise Induced Hearing Loss in the Ministry of Defence – role of defence hearing working group

Surgeon Captain David Brown QHP FFOM Royal Navy
Consultant in Occupational Medicine in the Royal Navy

The issue of noise induced hearing loss as a result of military operations was recognised in the immediate aftermath of the two World Wars, where personnel were exposed to intensive combat, however hearing protection was limited to the use of fingers and cotton wool. Subsequent to World War 2, and with the introduction of new military equipment including jet aircraft, major advances were made in the assessment of noise exposure and control measures, including hearing protection, thereby minimising the risk to service personnel. MOD made major efforts to comply with the Health and Safety at Work Act and subsequent Noise at Work regulations, and introduced comprehensive hearing protection programmes. Although weapon noise was long recognised and assessed as a hazard, with Peak Exposure Levels well above 140dB,  it was able to be controlled by hearing protection. However, after the increase in military activity in Afghanistan  from 2006 onwards it became clear that individuals were returning from theatre with Noise Induced Hearing Loss. Urgent action was taken by Land Command to mitigate this risk, and Surgeon General established the Defence Hearing Working Group to bring together all parties involved in the identification. prevention and management of noise induced hearing loss. Progress to date will be outlined and enlarged upon in subsequent presentations.

* Presentation: Noise Induced Hearing Loss in the Ministry of Defence – role of defence hearing working group (pdf file, 471kb)

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Operational Perspective

Col W. Bramble, AD PERS OPS
Chairman of the Army Hearing Working Group

Context:

  • Deployability of Army.  Army manning has a proportion that is either Non Deployable or limited deployable.  Including reference to those Soldiers employed on tasks.
  • Casualty figures.  Cover the current level of casualty figures in order to understand that Hearing Loss is part of the wider casualty management activity.

Occupational and Environmental Context. 

  • Magnitude of Problem.  After HERRICK 6 (Apr 08) HQLF received indication that HL was a problem generated on ops.  This coincided with the work by SG and the US on their Fallujah experiences.  The resulting early analysis of available audiometry showed the average inf bn HL was approx 6% of held strength.  Those inf bns returning from AFG on HERRICK 6 showed HL statistics of up to 14% of held strength.
  • Health Surveillance/ Audiometry.  The detail of audiometry and Health Surveillance will be covered by Lt Col Fiona Folkes later, but the requirement are set by JSP 346 for medical occasions (pre employment screening, routine PULHHEEMS occasions, for medical problems and when leaving the service).  Audiometry requirements due to Noise at Work regulations are contained in Army Hearing Conservation Programme which set bi annual (every 2 yrs) audiometry requirement with increased frequency for those at higher risk.  As a result of these early indicators from troops returning from AFG, it was decided, in Jun 08, that annual audiometry for all personnel would occur.  Furthermore, all personnel deploying on operations to AFG must have a pre deployment audiogram within 6 months of deploying and a post deployment audiogram within 6 months of returning from ops.
  • Operational Experiences.  Operational experiences since Falkland Islands (Balkans, GRANBY, TELIC) have not exposed HL as a significant issue due to the nature of conflict and operating environment.
  • AFG Operational Environment.  However, nature of conflict in AFG, which is significantly different has shown that the in service Hearing protection systems, particularly for those engaged in dismounted close combat, were ergonomically and functionally sub optimal.  Critically, the imperative to utilise all your senses to maximise situational awareness whilst engaged in dismounted close combat in complex terrain and fighting a counter insurgency operation forced many to make a stark choice of retaining situational awareness (including maintaining radio communications and verbal orders) as a short term life preservation essential subordinating the risk of HL to worry about if you were lucky enough to live to retirement.  Furthermore, the nature of COIN operations, and particularly in AFG, is such that there are very practical reasons why Hearing protection may not be worn at the critical moment and when you are least expecting it.
  • Formation of the Army Hearing Working Gp.  Met on 1 May 08 with aim to identify HL problems, provide a single army focus for HL and link into the Defence Hearing Working Group.  The tasks of the AHWG are to understand the problem; review and develop policy; issue direction; improve Health Promotion through education and culture change (which you will hear about from Lt Col Fiona Folkes later).  Finally, the Personal Interfaced Hearing Protection system, which you will hear about later, was brought into service as a result of the AHWG catalysing efforts.
  • Conclusion.  There has been much progress in terms of policy development; Health surveillance and monitoring; Health promotion and culture change; as well as new equipment for those deploying on operations.  Prevention and early identification remain the best way of approaching the issue of Hearing Loss.  However, consequence management remains a key area that we are focussed on in order to address those with Hearing Loss.

* Presentation: Operational Perspective (pdf file, 1.06Mb)

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The extent of operational noise-induced hearing loss

Surg Cdr Chris Pearson MBA MA FRCS(ORL) RN
Defence Consultant Adviser in ORL

A diagnosis of noise-induced hearing loss requires a history of exposure to sufficient noise and audiometric evidence of a high-frequency hearing loss of the appropriate configuration. Whereas exposure in industry may be assessed relatively simply, sporadic exposure to very high levels of noise generated by weapons means that this is not the case in the operational environment. In the Service hearing conservation programme it is, therefore, necessary to place greater reliance upon individuals' audiograms.

Newspaper reports in 2008 implied that between 5% and 10% of troops had become non-deployable due to NIHL on recent operations, but audit of their medical records shows that this was so in only one-third of cases.

Comparison of pre- and post-deployment audiometry in 100 Reserve personnel who deployed in Op Herrick 6 showed that 10% had a definite deterioration in their hearing and a further 32% had a measurable loss.

Of 181 Royal Marine 42 CDO troops who deployed in Op Herrick 9, 69% had audiograms that were consistent with NIHL. Both the proportion of affected individuals overall, and the proportion who were affected to a greater extent was significantly greater than a baseline study of RAF personnel that was undertaken prior to Op Herrick and Telic.

* Presentation: The extent of operational noise-induced hearing loss (pdf file, 471kb)

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Introduction to the ear, hearing and the effect of noise

Prof David Kemp
Emeritus Professor of Auditory Biophysics at University College London and Founder and Director of Otodynamics Ltd

The ear is a sensitive and delicate mechanism normally able to respond to ear drum movements smaller than the size of an atom. Today’s researchers access powerful techniques which can help us visualise the intricate mechanism of the ear at work.  Much more than just a microphone- the ear is an energetic machine able to manipulate, amplify and analyse sound energy on a nanometre scale before it is passed to the brain.

Its long been known that intense or persistent noise can permanently erode hearing sensitivity but the exact location and nature of this damage was unclear. Today we know that it is the energetic ‘engines’ of the ear – the ‘outer hair cells’ - which suffer most from the physical and biological stresses induced by noise. They become deactivated and eventually die causing a thousand-fold loss in hearing sensitivity.  We can record the progression of this damage with forensic precision.   Strengthening and even restoring these cells may be an option in the future but the immediate need is for practical means to detect the earliest signs of weakness in individuals before permanent hearing damage accrues.  Genetic studies should explain why some ears are much more susceptible to noise than others.

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Tinnitus – Gain, Pain and the Brain

Professor David McAlpine
Professor of Auditory Neuroscience and Director of the Ear Institute

Cochlear damage can trigger the development of central hyperactivity, but the underlying mechanisms remain elusive. Physiological studies indicate that the perception of tinnitus is linked to aberrant spontaneous activity (hyperactivity) of neurons in the central auditory system. Tinnitus-related hyperactivity has been found in the dorsal cochlear nucleus, the auditory cortex, and recently also in the inferior colliculus. Computational modelling indicates that activity stabilization through homeostatic plasticity could explain the development of hyperactivity and tinnitus. This presentation will describe some of the possible causes and consequences of tinnitus, including the possibility that noise-induced hearing loss not detected by conventional audiometry, can elicit tinnitus symptoms. Mechanisms contributing to the tinnitus percept may be related to normal brain mechanisms that control sensory gain. The outcome can be likened to phantom limb pain, where the absence of sensory input is compensated for by modifications of the neural representation of the damaged or missing limb.

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Research into Noise Induced Hearing Loss

Captain Montcalm Smith and team ONR
US department of Defense

This presentation summarises research into Noise Induced Hearing Loss.

* Presentation: Research into Noise Induced Hearing Loss (pdf file, 799kb)

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Limiting exposure to noise

Lieutenant Colonel Sef Folkes
Consultant Occupational Physician Army Medical Directorate 

Service life exposes personnel to many occupational hazards that differ from the civilian environment, in the non operational environment the risk of these hazards causing harm can be addressed and have been reduced to the lowest practicable level to meet and in many cases better than that which is required by the legislation.  In the operational environment, the increasing tempo of operations and exposure to novel noise hazards increases the risk of noise induced hearing loss.

The principles of reduction of exposure to all occupational hazards also apply to noise exposure in the military. The principles of limiting exposure are laid out in a number of policy documents JSP 375, 2006DIN07-008 Implementation of Noise and Vibration at Work Regulations 2005  and in the Army this is further interpreted in the and Forces Standing Order 3303 - Land Forces Hearing Conservation Policy.
Non–deployable Environment – key identification of potential noise hazards this is undertaken by line managers and unit safety officers.  Areas to cover are identification of potential noise hazards, identify persons at risk, arrange for a noise assessment, reduction of risk , provision of appropriate hearing protection, ensure arrangements are made for health surveillance, hearing protection zones, education, monitoring noise control measures and consultations including Unit Health Cttes.

Operational and Overseas training exercises - personnel are exposed to a wide variety of potentially damaging noise sources that cannot always be identified and managed.  As part of the health force protection measures each operation and exercise has specific measures and hearing protection measures outlined in the mounting instructions.  Where possible the options must be taken to taken to ensure the use of hearing protection when predictable noise exposure is planned e.g. wearing hearing protection when transiting in an aircraft or armoured vehicles

Education

  • Extensive work has been undertaken over the last year to develop additional hearing protection education material.
  • Production of a 10 minute DVD ‘Listen to Sense’ which is targeted at Service personnel in Initial Training but for use throughout a career to highlight the fact that hearing loss can be caused by operational contacts, firing weapons, operating machinery unprotected or listening to loud music .  Highlights hearing loss is progressive, often painless and permanent and importantly will have significant effect on promotional chances and the ability to deploy on operations.  The DVD is supported with additional material to guide the presenter though the discussion that should follow watching the film.
  • Supported by Commanders guide and Individuals Guide as well as posters x 3
  • There have been slots on Garrison radio complementing the Listen to Sense programme and it is covered at Regional Health Fairs.
  • Army Net open will also shortly have a Listen to Sense section with the educational material.
  • DVD to be shown ‘Listen to Sense - Protect Your Ears’ - 10 minutes

Screening

  • Audiometry as Health surveillance is part of the Army Hearing Conservation Policy.
  • Frequency and means of testing, grading and interpreting laid down in MOD policy and further supplemented by single service guidelines.
  • JSP 346 pre-employment screening and then SGPL 12/06 and 05/09 provide medical guidelines. Army DGAMS policy letter 09/08 Health Surveillance for Noise at Work in the Army and specific employment groups have additional requirements e.g. aircrew.
  • Army now require audiometry to be undertaken pre-entry, at Service PULHHEEMS, annually and within 6 months prior and after operational deployment (this should fulfil annual requirement, on discharge or retirement and at the discretion of the clinician.

* Presentation: Limiting exposure to noise (pdf file, 648kb)

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Hearing Protection Dismounted Infantry

Mrs Gillian Williams - SE CESO ASE Noise DE&S
Defence Equipment and Support

Gill will discuss the background and range of equipment that MOD supplies to meet the requirement before going on to cover the MOD’s work towards procuring equipment to meet changing needs of infantry soldiers.

* Presentation: Hearing Protection Dismounted Infantry (pdf file, 719kb)

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Potential for pharmacological intervention in noise-induced hearing loss

Andrew Forge
Centre for Auditory Research, UCL Ear Institute

With the exception of intense blast noise which causes complete, irreversible disruption of the sensory tissues of the cochlea, the major cause of noise-induced hearing loss (NIHL) is the death of the sensory “hair” cells. Once lost, hair cells are not replaced so the consequent functional deficit – hearing impairment – is permanent. Understanding the biochemical pathways that lead to hair cell death and how they are triggered by noise has indicated possible means for pharmaceutical intervention to prevent or ameliorate hair cell loss. One major trigger initiating the cell death programmed is excess production of  “free radicals”, highly reactive forms of molecular species that breakdown cell components. Noise exposure leads to free radical generation in the cochlea. Some potential “otoprotectants” target specific components of the cell death pathway, but these may difficult to deliver to the cochlea easily. A number of  different “anti-oxidants”, which “scavenge” free radicals and neutralise them or enhance natural cellular scavenging systems, have been suggested to reduce the extent of noise-induced hair cell loss. Many of these chemicals are small molecules able to cross the physiological “barrier” between the blood supply and the cochlear fluids, and thus potentially could be taken systemically. However, the doses required, and for how long before and/or after exposure to traumatising conditions such dosing needs to continue are not known.

* Presentation: Potential for pharmacological intervention in noise-induced hearing loss (pdf file, 3.18Mb)

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Fitness for work and occupational rehabilitation for NIHL within the MOD

Lt Col Holden
Consultant in OM since 1997 and responsible for advising SG since Oct 2008.
Defence Medical Services Department

The presentation will cover:

  • Current UK hearing acuity grading system
  • Linking this system to deployability on military operations
  • A proposed future hearing acuity grading system
  • Management of potential NIHL cases
  • Looking at knowledge gaps (true prevalence, consistency and quality monitoring of audiometry
  • Opportunities to improve future knowledge – more research, use of DMICP data

* Presentation: Fitness for work and occupational rehabilitation for NIHL within the MOD (pdf file, 648kb)

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Integrating hearing and balance services: vision, benefits and challenges for populations who serve in armed forces

Professor Adrian Davis BSc, MSc, PhD, FFPH, FSS, O.B.E
Director MRC Hearing and Communications Group, University of Manchester Director of the Newborn Hearing Screening Programme for England.

There has been much debate about the extent to which noise exposure in young people affects their hearing in later life. There has been no formal consensus but an agreement that noise, especially the noise experienced by ex-service personnel, is a major public health issue in later life that needs to be addressed. Clearly prevention is best. But prevention is only part of the major issue which is how those who have immediate or later impacts of noise get the best quality services to reduce the impact on activities that people normally need to do or enjoy doing. The later impacts are usually dealt with reasonably effectively by the NHS, but the age at which people realise there is a problem is often too late. Recognition that ex service personnel are at raised risk of developing hearing problems needs to more widely disseminated and it is not unreasonable to think that a targeted screening programme would idenitfy those with hearing problems that can be addressed by hearing rehabilitation would have substantial quality of life benefits. These should be routine innovations that could be introduced if there was a governance and funding stream agreed. But do we need to think about equity as well? Beyond hearing loss the situation is more complex. It is not just hearing problems, but more complex issues regarding tinnitus, balance and other impacts that noise and trauma may create. The NHS is not necessarily well equipped to look at these longer term more complex issues. How should it respond, what partnerships are necessary to improvce current services and is there a need to establish a baseline for what NHS services ex service personnel are currently receiving for these problems?

* Presentation: Integrating hearing and balance services: vision, benefits and challenges for populations who serve in armed forces (pdf file, 903kb)

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US Experience

Stephen Fausti PhD
Director, National Center for Rehabilitative Auditory Research (NCRAR)

  • Auditory dysfunction is the most prevalent service-connected disorder
  • One in four service members returning from OEF/OIF conflicts complains of hearing loss and/or tinnitus (Fallon, 2006)
  • As the Veteran population ages, hearing loss will become more prevalent and more Veterans will require rehabilitation
  • Effective hearing loss prevention strategies must be implemented in order to reduce the financial and personal costs of auditory disabilities
  • For the veteran, the most relevant cost is the reduction in “readiness for life”

* Presentation: US Experience (pdf file, 2.37Mb)

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