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Noise Study

NOISE Study: Examining Hearing Loss, Tinnitus in the U.S. Military

Schultz, James AuD; Cline, Jordan MS; Griest, Susan MPH; Grush, Leslie AuD; Henry, JamesA. PhD

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doi: 10.1097/01.HJ.0000689448.28258.92
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Hearing loss and tinnitus can occur due to noise exposure and may be associated with adverse effects on overall well-being due to anxiety, depression, sleep disorders, and various comorbidities.1 Determining the exact cause, circumstances of onset, and contributing factors to hearing loss and/or tinnitus can be challenging. In some cases, hearing loss can be attributed to a singular medical cause such as a disease, genetic condition, autoimmune disorder, medical treatment, or head trauma. However, in many individuals who are diagnosed with bilateral sensorineural hearing loss, the root cause may be difficult to determine, especially when considering a lifetime of exposures to noise and other ototoxicants. Evidence from animal research suggests that noise exposure may result in delayed-onset auditory system damage, which means that traditional audiometric testing may not immediately reveal noise-related auditory damage.2 Additionally, tinnitus is an entirely subjective experience that cannot be measured directly, and time-consuming psychoacoustic testing for tinnitus is not feasible in many clinical situations.3 Lastly, it can be difficult to accurately and precisely assess how hearing loss and tinnitus may have impacted a patient's quality of life; such an assessment relies on subjective patient reports usually gathered in conversations during a clinical appointment.

Shutterstock/wavebreakmedia, audiology, noise, military.

As audiology clinicians, our responsibility includes educating patients about factors that may contribute to hearing loss, helping them understand what may have caused the loss, mitigating hearing loss progression to the extent possible, and developing plans for future management of hearing loss and/or tinnitus. However, clinical appointments do not always allow adequate time for thorough and accurate case history review. With limited information derived from a case history and audiologic assessment, it may be difficult to determine the cause, onset, and risk for progression of auditory decline. To accurately understand an individual's hearing history as it relates to noise exposure, detailed information is needed about types, extent, and frequency of exposures throughout the patient's life. It is challenging but important to consider the fullest possible range of potential noise exposure, such as musical concerts, sporting events, fireworks, lawn equipment, noisy restaurants and bars, firearms, and motorsports. Assessment is all the more difficult because there is no widely accepted and meaningful way to interpret and quantify all relevant exposures. Audiologists must primarily hypothesize how a patient's noise exposure history may contribute to the eventual onset of hearing loss and/or tinnitus, and exercise best clinical judgment based on experience to project future outcomes. Audiologists use Occupational Safety and Health Administration (OSHA) and National Institute for Occupational Safety and Health (NIOSH) exposure guidelines to counsel patients on the proper use of hearing protection to prevent auditory damage, but have few options when counseling to explain hearing damage that may have already occurred.

Epidemiologic research is needed to better understand longitudinal relationships between noise exposure, hearing loss, and tinnitus.4 To address these relationships, the Noise Outcomes in Service Members Epidemiology Study (NOISE Study) was developed as a joint effort by the Department of Veterans Affairs (VA) Rehabilitation Research & Development (RR&D) National Center for Rehabilitative and Auditory Research (NCRAR) in Portland, OR, and the Department of Defense (DoD) Hearing Center of Excellence (HCE) in San Antonio, TX.5 This article explains the importance of longitudinal epidemiologic research as it relates to hearing health care, describes the data collection methods of the ongoing NOISE Study, and discusses how some NOISE Study tools can be used in clinical practice to improve patient outcomes.

NEED FOR LONGITUDINAL EPIDEMIOLOGIC RESEARCH

Active duty military service members and veterans may be more susceptible than the general public to hearing loss and tinnitus, likely due to risk factors associated with military service, including noise exposure, chemical and blast exposures, and traumatic brain injury (TBI).6 In 2018, tinnitus and hearing loss were the two most prevalent military service-connected disabilities, with over two million cases.7

In 2006, the Institute of Medicine (IOM) acted on a congressional mandate to address issues related to hearing loss and tinnitus in the military. The IOM published “Noise and Military Service: Implications for Hearing Loss and Tinnitus,” which encouraged researchers to collect longitudinal data from service members and veterans relating to military and nonmilitary risk factors, auditory function, presence and severity of tinnitus, and other potentially correlated variables.8 The objectives of the IOM's recommendations were to learn more about the onset of hearing loss and tinnitus and how they change over time. This type of research would help to identify cohorts at greatest risk for auditory injury, guide effective hearing conservation programs, inform the development of advanced treatments to mitigate the underlying causes of hearing loss, and determine whether delayed-onset hearing loss and/or tinnitus occurs in humans. The NOISE Study was initiated as a direct result of the IOM's recommendations.

NOISE STUDY: THE MORE DATA, THE BETTER

The NOISE Study, which began recruitment in 2014, aims to determine the prevalence, etiology, and effects of early-onset tinnitus and hearing loss among military service members in active duty and those who have recently left (within the past two and a half years ).5 Ultimately, this will involve a cohort of at least 1,500 participants and longitudinal annual follow-up data. Data collected for the study include noise and ototoxicant exposures, audiometric measurements, pre-existing medical conditions, including a history of TBI and mental health conditions, and perceived effects on quality of life. Recently, separated service members are being recruited to participate in the NOISE Study at the NCRAR, and active duty service members are being recruited at the HCE. To date, over 1,000 participants have been enrolled.

Longitudinal and epidemiologic studies lend themselves to collecting an abundance of data. The NOISE Study captures comprehensive audiometric measures gathered through pure-tone air conduction (0.25-16 kHz) and bone conduction (0.5-4 kHz) audiometry, immittance testing (tympanometry and acoustic reflexes), speech audiometry (speech reception thresholds and word recognition), Speech Recognition in Noise Testing (SPRINT), dichotic digits testing, distortion product otoacoustic emissions (DPOAE), and, when applicable, tinnitus loudness match, pitch match, and maskability testing (minimum masking level). This thorough audiometric evaluation takes approximately 90-120 minutes conducted first at the time of enrollment and then repeated every five years.

The NOISE Study also administers multiple questionnaires (15 for all participants, 18 for those with tinnitus) upon enrollment into the study, prior to audiometric evaluation, and again annually over the life of the study. In the first five years of the study, questionnaires were administered as paper forms in packets of up to 70 single-sided pages. Many participants found it cumbersome to manage and return the bulky questionnaire packets every year. This led to frequent data collection and processing lags and the need for time-consuming reminder phone calls and e-mails. In late 2019, all NOISE Study questionnaires were converted to an electronic format and made accessible via a web-based, HIPAA-compliant data collection tool (Research Electronic Data Capture or REDCap).9,10 While the use of this platform is still relatively new to the NOISE Study, we have already seen faster and higher rates of return on the annual follow-up questionnaires and observed fewer data error incidents.

POTENTIAL CLINICAL UTILITY

The NOISE Study's successful transition to an electronic data collection platform highlights the potential value of automated data collection for clinical purposes. Clinical appointment time is frequently limited, forcing clinicians to prioritize and manage their time carefully and to consider what can be done to make clinical encounters as effective and beneficial as possible for patients. While it is not possible to administer all available instruments and outcome measures that might be informative, some of the NOISE study questionnaires could be implemented practically in clinical settings. Instead of asking patients to spend an additional 60 minutes in the medical office to fill out questionnaires, they could be given the option to complete the questionnaires electronically at their convenience before or after their appointment and from the comfort of their own home. This may help clinicians develop a more comprehensive understanding of their patients, and, in turn, give patients more confidence in the thoroughness of their care and treatment plan. The following questionnaires used in the NOISE Study could be of interest to practicing clinicians.

Tinnitus Screener (TS). This six-item tool was designed to determine the presence of tinnitus and to categorize identified tinnitus as constant, intermittent, occasional, or temporary.11 It also determines whether tinnitus is acute (more than six months) or chronic (less than six months). The TS takes only two to three minutes to complete, and can be included as an initial tool if a patient has specific questions about tinnitus, part of a routine case history, or administered before or after audiologic assessment. It can be a helpful starting point for counseling to determine whether intervention for tinnitus may be necessary.

Tinnitus and Hearing Survey (THS). When determining the need for clinical intervention, it is essential to distinguish between tinnitus and hearing difficulties.12 The THS is a 10-item instrument that can be used to distinguish problems due to tinnitus from those due to hearing loss or decreased sound tolerance (hyperacusis).13 Patients often describe their hearing difficulties as tinnitus, or vice versa. For these cases, the THS, which was designed to assess subjective distress related to a specific issue, can be used to examine hearing and tinnitus complaints separately. Two survey items address hyperacusis since this is often reported by patients who have tinnitus.

Many patients with hearing loss are hesitant to proceed with hearing aids. They may be unaware that tinnitus and hearing loss can be related, so they don't consider amplification to be potentially therapeutic for tinnitus. The THS may help in developing a better understanding of the source of a patient's auditory complaints.

Lifetime Exposure to Noise and Solvents Questionnaire (LENS-Q). This is an in-depth, self-report questionnaire used to quantify a lifetime history of continuous and impulse noise exposures as well as exposure to potentially ototoxic chemicals/-solvents from military occupational, non-military occupational, and non-occupational/recreational sources.14 Respondents are asked yes or no exposure questions in each section. Those who answer yes are asked to provide information concerning exposure duration, frequency, and use of hearing protection or other safety equipment. These details are essential to the longitudinal epidemiologic identification of potential risk factors for hearing loss and tinnitus.

Although the LENS-Q is not yet available for clinical use because the normative data have not yet been published, this instrument could eventually provide a basis for standardized scoring that describes an individual's risk level for hearing loss due to noise or chemical exposures. On average, the questionnaire takes 30 minutes to complete. If made available for completion prior to an audiologic clinical appointment, its findings could be very helpful as a framework for counseling.

Determining the onset and cause of hearing loss can be difficult, especially for patients who present with a lengthy history of noise and/or solvent exposure. No universally accepted method exists to identify individuals who are at increased risk for hearing loss based on exposure history, and no tool can effectively predict the impact of noise exposure on auditory function later in life. The ongoing NOISE Study aims to evaluate such effects in military service members and veterans. Tools and methods that have been created and/or implemented for the NOISE Study can also benefit patient outcomes in the audiology clinic setting. These tools can be adapted to obtain standardized measures and provide helpful perspectives to guide management plans.

Editor's note: The U.S. Army Medical Research Acquisition Activity, 820 Chandler Street, Fort Detrick MD 21702-5014 is the awarding and administering acquisition office. This work was supported by the Office of the Assistant Secretary of Defense for Health Affairs, through the Joint Warfighter Medical Research Program under Award No. W81XWH-17-1-0020. Opinions, interpretations, conclusions, and recommendations are those of the authors and are not necessarily endorsed by the Department of Defense. The use of REDCap acknowledges support from grant No. UL1TR002369.

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