Hearing loss and tinnitus are the top two diagnoses among Service Members of Operations Enduring Freedom and Iraqi Freedom.¹ They are also the most prevalent disabilities recorded for Service Members who served during World War II, the Korean Conflict, the Vietnam Era, and during peacetime periods.¹ Among Veterans, impairment of the auditory system is consistently documented as the second most prevalent bodily system injury after musculoskeletal disabilities.¹ Service-connected disability for hearing loss and tinnitus continues to rise annually, as does the total amount spent on these disabilities.^1,2 Estimates approach $1.2 billion of entitlement for compensation and care of hearing loss and auditory system injuries in over 1.8 million Veterans in 2012 alone.³ Despite efforts to emphasize and improve military hearing conservation programs (HCPs), between 10% and 18% of Service Members enrolled in such programs annually have been diagnosed with significant threshold shifts in their hearing, representing a prevalence of two to five times higher than rates in comparable civilian, industrial HCPs.⁴ However, the actual economic burden of this highly prevalent health condition is not well characterized in active duty populations.

Previous studies addressing the economic burden of hearing loss have focused on the civilian population,⁵ and several studies analyzed U.S. Veteran cohorts.⁶ For example, the Centers for Disease Control and Prevention estimated the disability cost of occupational hearing loss was $242.4 million per year nationally. Based on a report from Washington State in 1991, hearing-related conditions cost about $4.8 million in workers’ compensation disability settlements.⁷ Despite a high prevalence of hearing loss and noise-induced hearing injury and the associated high economic burden, there are no recent, comprehensive, and reliable estimates of costs incurred by the Department of Defense (DoD). In addition, published estimates exclude additional expenses related to hearing loss that are not as transparent. These include outpatient expenditures (ear examinations), travel expenses, productivity losses (reduced income, work absences, reduced lifetime earnings, reduced working hours, early retirement, unemployment, under-employment), support services (special education classes, interpreters, note takers), assistive devices, cost of communication devices (telephone, speech aids), vocational rehabilitation, and out-of-pocket expenses. Auditory impairment also affects total force management through medical dispositions, limitation coding, and retraining with secondary effectors altering operational tempo of nondisabled troops and recruitment needs. The actual economic cost of hearing loss is likely to be higher than what is reported in published estimates.

The goal of this multiphased research effort is to determine the comprehensive economic burden for hearing injury and noise-induced hearing injury among active duty U.S. Service Members. This first phase as reported in this article focuses on developing methods to determine the economic burden from the perspective of the DoD.

The objectives of this study include the following: (1) to identify, define, and categorize all relevant costs incurred by the DoD related to preventing and managing Service Member hearing impairment and noise-induced hearing injury; (2) to develop a flow chart representing an active duty Service Member’s career span to conceptualize potential permutations of hearing outcomes across the continuum of hearing health and injury; and (3) to develop an analytical framework and statistical model to represent the cumulative economic effect of events along the career span, by synthesizing inputs from various sources and projecting the economic burden caused by hearing impairment and noise-induced hearing injury.

To develop a framework and statistical model for economic burden analysis, several steps were undertaken. A literature review involved an in-depth search to identify studies that have reported the cost of health conditions and injuries in the DoD. Published studies and reports on HCPs, epidemiology of hearing loss, recruitment and retention statistics, and demographic profiles of active duty Service Members were also collected and synthesized. Studies were summarized in a background document, and an initial listing of cost items was developed. Our study team assembled an expert panel of Subject Matter Experts (SMEs) to review this initial list of cost items, categorize them into meaningful broad groups, and identify DoD data sources with variables relevant to calculating these costs. The expert reviews involved extensive in-person, e-mail, and telephone consultation.

SME composition included ear-nose-throat doctors, audiologists, industrial hygienists, military training personnel, and HCP officials with work experience with the DoD and Veterans Administration. The SMEs clarified the research team’s understanding of (1) existing Service HCPs, (2) organizational structure, type, and staffing/personnel levels within Service HCPs, and (3) hearing-related workflows of DoD operations. After the initial framework and model were constructed, SMEs also reviewed the “model pathway and components” and commented on its validity, utility, and ease of use. An environmental scan of the data sources, including discussions with DoD data stewards and review of data dictionaries for relevant databases, provided a realistic situation assessment for the research team to further refine the framework and plan for implementation of cost burden models.

Finally, we synthesized input from various sources to develop a Markov model based on a Service Member’s career trajectory, including influence and interaction of HCPs, attrition numbers, and need for retraining after hearing loss. This type of model is a useful tool for an economic burden analysis for any heath condition, illness, or injury.^8,9 Within a Markov model, the natural history of a disease is represented by multiple mutually exclusive health states, and individuals move between these health states with the cyclical transition probabilities over time. The length of a cycle depends on the disease and on the interventions that are being evaluated. The average amount of time that an individual spends in the various states of the model is then associated with costs or utility, which will be used to calculate the expected values of costs and health outcomes. For this study, Markov model states will be represented by events associated with auditory impairment.

Evidence-based decision making in public health increasingly demands that the allocation of research and program funds consider all the costs and consequences of diseases competing for limited resources. Studies on cost of injuries and illnesses are important for providing information on (1) the burden of injury/illness; (2) the comparison of cost burdens of different injuries and illnesses; (3) cost inputs to be incorporated into economic evaluation studies including cost-minimization, cost-effectiveness, cost-utility, and cost-benefit analyses; (4) the most influential cost drivers of specific injuries/illnesses warranting prioritized prevention efforts; and (5) past trends in costs and projection of future costs.^14,15 For occupational injury and illness, a broader, societal perspective analyzes costs that accrue not only to the employer, health care system or the insurance provider but to the worker or society in general.

In subsequent phases of this study, the direct and indirect costs incurred by DoD for hearing loss will be quantified using the framework and Markov model as proposed, and using different available secondary and administrative data sources identified in the present phase. Factors influencing the economic impact will be described (e.g., severity of hearing loss, region of duty station, military occupational specialty). Other factors introducing variance and inaccuracy into the model will also be discussed, such as the general trend toward delayed diagnosis, and cumulative losses that accrue within and between stages and transitions that build over time without triggering sensitivity thresholds.

Suboptimal resource allocation often arises because of partial accounting of hearing loss costs as evidenced in earlier studies. There will be a broad-based stakeholder involvement at every step which will ultimately help DoD decision makers to understand and capture the full range of costs associated with this preventable health condition. Outputs from this study will provide decision makers with a valuable tool for future decision making on resource allocations.

If risk and cost data are extended to include risk factors for hearing injury and noise-induced hearing injury, comorbid disease components and relevant costs, then cost burden modeling can be performed on simultaneous multidisease or multi-injury assessments. This will allow certain comorbidities of hearing loss to be included in the risk assessment modeling (e.g., traumatic brain injury, post-traumatic stress disorder, tinnitus). Investigation of sensitivity analyses in this model can be performed by establishing an uncertainty range for each input, then exercising the model many times, using an algorithmically calculated input that varies randomly within the uncertainty range for each input.

There are some limitations associated with such modelling. First, data necessary to calculate incidence and event probabilities across the demographic variables are often not available for the active duty population. Second, privacy concerns and the de-identification methodology may interfere with the calculation of model parameters for some demographic value combinations. Next, data availability for deployment timelines may constrain the ability to calculate probabilities and other parameters related to the deployment state.

Another concern is the frequency of audiometric testing and costs thereof, which may depend on the frequency and duration of deployment, and may occur more frequent than annually. Also, some processes occurring in hearing injury and noise-induced hearing injury intervention may be poorly represented with an annual cycle length, such as multiple clinical encounters for assessment and fitting of hearing assistive and rehabilitation devices.

Hidden hearing injury and noise-induced hearing injury is also a concern, particularly for those injured while deployed, as a hearing injury and noise-induced hearing injury is less likely to be observed and reported in the presence of other potentially life-threatening injuries. When a hearing injury is unreported, the calculated incidence rate will be lower than the actual incidence rate.

Finally, despite our efforts to capture, categorize, and define all relevant costs, our study may not be able to identify appropriate data sources to estimate every cost. However, the items identified and discussed will be useful references for future studies that plan to investigate injury and illness.

However, despite the limitations inherent in the available data, our cost estimates may be the most complete to date. Further, the use of the Markov model is an innovative advance to cost burden studies of hearing loss. This model allows multiple independent and mutually exclusive categories to be combined using observational data to estimate transitions, provides a coherent and systematic way to simulate complex processes, and produces cost burden estimates for each component as well as total cost.

To our knowledge, the models as developed and proposed in this study, have not been previously used in the DoD to calculate the economic burden of hearing loss conditions. Despite its dependence on a number of assumptions and the fact that reliable and valid outputs depend on accurate, complete, and comprehensive data inputs, these models should prove to be a valuable decision-making tool for DoD policy makers. This tool could identify high-burden groups, enable proactive measures for concerted education and training, identify best practices to standardize, and develop return-to-duty programs following hearing injury and noise-induced hearing injury, all of which may lead to retention of skilled, experienced, and mission-ready Military personnel.