Military audiology has achieved cutting-edge research advances, including boothless audiometry for detecting hearing loss in soldiers who are still on the battlefield, new protective devices that prevent noise-related hearing loss while preserving soldiers’ situational awareness and safety, and animal models that are uncovering the mechanisms behind blast injuries.
These impressive research efforts are often done in conjunction with daily, more prosaic but no less important tasks, such as helping fit service members with hearing aids and treating them for the debilitating effects of tinnitus.
Isaac D. Erbele, MD, a lieutenant colonel in the U.S. Army and a neurotologist at Brooke Army Medical Center (BAMC) in San Antonio, Texas, embodies this bench-to-bedside approach. “I have a busy case load both at BAMC and at the South Texas VA,” Dr. Erbele said. “I go back and forth between active duty and veteran populations,” focusing on conditions typical of military personnel, including noise-induced hearing loss and tinnitus. But research is also a keen interest for him.
“I am doing everything from bench studies all the way up to clinical trials, because I pride myself in being a truly translational researcher,” Dr. Erbele said. Many of those research projects are done, he added, via his connections with the Department of Defense (DOD) Hearing Center of Excellence, in San Antonio, and the Uniformed Services University of the Health Sciences, in Bethesda, Md.
One area Dr. Erbele is most excited about involves the use of otic organoids, which are laboratory-grown, three-dimensional structures derived from stem cells that model the inner ear. “Basically, we’re trying to take human pluripotent cells to approximate cochlear hair cells and determine what kind of mechanisms occur with blast trauma to see if there are opportunities for therapeutic interventions,” he explained. “That’s been a little slow-going, but I’m hopeful that we get some publications out soon.” (For more details on otic organoid research, see a recent review coauthored by Dr. Erbele: Bioengineering (Basel). doi: 10.3390/bioengineering11050425).
“We are also doing several blast studies in rats and sheep where we introduce at least temporary, if not permanent, hearing loss threshold shifts and then test several therapeutics to improve the animal’s hearing after their noise trauma,” he said. “So far, we’ve looked at anti-inflammatory agents and have seen some very encouraging results.”
Dr. Erbele is also working on a nerve regeneration therapeutic model in larger animals, “which is great because it affords a closer approximation of the human cochlea and hearing. So, there’s an opportunity for more translational work as well, which we are very excited about.”
Prevention: a Good Place to Start
Although such research efforts are rewarding, Dr. Erbele’s primary focus remains on caring for the hearing health needs of military personnel. As with many clinical conditions, when it comes to hearing loss, prevention is key. For active military personnel, that means the use of hearing protection devices. But that’s not always easy. One of the most difficult places to use such devices is in the field, where service members often have mixed feelings about a device that may adversely affect their situational awareness, safety, and effectiveness during battle or other risky deployments, Dr. Erbele noted. The answer to meeting that challenge, he said, is twofold: education and improved technology.
The education component “comes down to convincing service members that if they don’t use hearing protection, they likely will suffer hearing loss that can hurt their ability to perform on the battlefield or even to continue in military service,” he said. Although baseline thresholds for hearing function vary based on the type of military activity, “our service members need to know that using these hearing protection devices correctly can ensure they continue to meet those performance thresholds.”
There have been some encouraging developments in hearing protection technology, Dr. Erbele noted. He cited, as an example, the 3M PELTOR system, which was designed for combat and combat support operations in conjunction with firearms and ballistic combat helmets. The system employs hearing protectors featuring external microphones that allow for environmental listening, so that “operators can maintain auditory situational awareness,” while safeguarding them from loud noises and other insults in the field, according to the manufacturer (3M. bit.ly/3HXrOUK).
Hearing protection fit testing is another important key to ensuring optimal use, Dr. Erbele stressed. Under a November 2023 mandate from the DOD, fit testing has to be done in all military personnel who have documented noise exposures greater than or equal to 95dBA and who are enrolled in a service hearing conservation program, according to Health.mil, the official website of the Military Health System (https://bit.ly/4oYDJ5g).
“It seems very obvious, but the better these hearing protection devices fit an individual service member, the more likely they are to use them,” Dr. Erbele said.
Jason Adams, MD, an otolaryngologist and researcher at Brooke Army Medical Center in San Antonio, Texas, applauded the DOD’s 2023 mandate for fit testing. “If you just have one day of exposure to occupational noise or some other insult, you have to get fit-tested,” said Dr. Adams, who is a major in the AirForce. “Of course, it’s up to the units to implement the new policy. But it’s a good one and should yield some improvements in terms of prevention, although I haven’t seen that data yet.”
Dr. Adams agreed that convincing service members to wear protective devices can be a challenge, even after ensuring a good fit. Echoing Dr. Erbele, he noted that concerns over situational awareness are one of the most common reasons for pushback. “But I’ve also found that a bit of education on that score goes a long way,” he said. “I try to make them understand the implications of losing hearing from even one occupational noise exposure, not only in terms of their own quality of life but also their ability to support their unit effectively, not to mention remaining deployable. Plus, there can be administrative punishments for not wearing protective devices. That messaging really resonates.”
John Marinelli, MD, a neurotology fellow at Mayo Clinic in Rochester, Minn., also has found that education can help improve compliance with hearing protection devices. But he cautioned that it doesn’t always work. “I have plenty of friends who are in the infantry, and they tell me there’s a real incentive to take their hearing protection out when they’re in the middle of a firefight because you must hear the people around you to stay safe and effective in battle. So, in some cases, they are going to risk hearing loss to make sure they and their fellow soldiers stay alive.”
That’s why the new improvements in hearing protective devices are so encouraging, noted Dr. Marinelli, who spent five years as a neurotology resident in the San Antonio Military Medical Center, managing hearing-related conditions in active-duty service members and veterans.
An Early Warning System
Screening is another important tool, if not for preventing hearing loss, at least for intervening as early as possible. Dr. Erbele cited an innovative technology known as boothless audiometry, where personnel can be fitted with specialized headphones to gain an accurate reading of their hearing thresholds. To date, the technology has been used in two successful pilots, with another pilot in progress, according to a VA Diffusion Marketplace report (bit.ly/4g2bCOt).
Samuel A. Spear, MD, who spent three years as the chief of the DOD’s Hearing Center of Excellence when work in boothless audiometry was done, lauded the technology. “It’s important to be able to get screening done in a way that fits in with the realities of military life,” said Dr. Spear, who is now in private practice at ENT and Allergy Associates of Florida. “Boothless technology allows us to detect hearing loss much earlier than would otherwise be feasible and get noise-exposed service members to treatment quicker, whether it be steroids or hearing aids or other interventions.”
Dr. Adams is yet another fan of boothless audiometry. “It should be very effective in identifying acute threshold shifts from hearing loss in the field,” he said. “The sooner we can treat that hearing loss, whether it be with oral or injectable steroids or some other therapeutic, the better.”
He also noted that boothless audiometry is just one example of impressive work done on screening by the DOD. He cited as an example the DOD’s Hearing Conservation Program, which includes baseline hearing tests done as early as possible in a service member’s military career. Those individuals are then screened annually for threshold shifts that might denote hearing changes.
“When active-duty personnel leave the service, they are given another audiogram,” Dr. Adams said. “That way, neurotologists, audiologists, and other clinicians in the field are well positioned to address any hearing loss that is detected as these service members enter civilian life.”
Dr. Marinelli said he has grown to appreciate the breadth of screening protocols for hearing loss in service members. “If they’ve experienced a deficit, we can detect it and intervene early,” he said. Nevertheless, “it still takes a lot of hearing loss—and time—to be caught by screening. If you look at audiograms in people after years of noise exposure, often it’s the high frequencies—around 4,000 hertz—that tend to be disproportionately affected.”
In such cases, he added, normal speech frequencies are preserved, which makes awareness of the condition problematic. But over time, the hearing deficits, often accompanied by tinnitus, tend to accumulate. “That’s why if you look at reimbursement for veterans’ care, hearing loss and tinnitus are the number one and number two most compensated disabilities in the U.S.,” he said.
Good News on Hearing Aids
Once hearing loss has occurred, other interventions are needed, with hearing aids one of the most common treatments. The good news for military personnel is that coverage for these devices is significantly better than in the private sector, where most state Medicare and Medicaid plans do not include hearing aid benefits; private insurers offer similarly limited coverage. That’s according to one of the largest studies of hearing aid coverage conducted to date, by researchers at the USC Caruso Department of Otolaryngology–Head and Neck Surgery, in Los Angeles (bit.ly/4nlaI2l).
Dr. Erbele underscored the importance of this coverage. “All of our active-duty service members and their dependents, as well as our veterans, have access to free hearing aids, which is a really nice benefit.” He added that “everybody should have that same benefit,” but at least for service members, “it is definitely nice to be able to rely on hearing aids to make sure we’ve done everything possible for a patient’s hearing loss rehabilitation before talking about other interventions.”
One such intervention is cochlear implants (CIs). In the civilian population, as with hearing aids, access to CIs remains a challenge, with utilization rates lagging far behind the number of patients who are eligible for the procedure. In one study, investigators estimated that only between 2% and 13% of people in the U.S. undergo CI, depending on the audiometric CI criteria used (Otol Neurotol. doi: 10.1097/ MAO.0000000000003513).
Dr. Erbele said he was not aware of any data on CI utilization rates in the military, but he certainly is aware of the overall nationwide trend of low CI uptake, because he and fellow researchers cited this low uptake in their own review of CI trends (Laryngoscope. doi: 10.1002/ lary.32037). Dr. Erbele and his colleagues offered one potential fix: making CI surgery a requirement for otolaryngology residency education. “This would ensure that general ENTs actually have that skill,” he said. “Of course, it’s one piece of a much bigger puzzle for increasing CI utilization. But it’s an important one: If our surgeons in GME [graduate medical education] programs—including our own in the military—have the ability to perform CIs, then more patients who need them will get them.”
Tackling Tinnitus
Tinnitus is another common condition that Dr. Erbele and his military audiology colleagues often see in their patients. The two conditions are strongly linked, with some research suggesting that up to 80% of patients with unilateral or bilateral tinnitus are also diagnosed with hearing loss using standard pure-tone audiometry (Front Neurol. doi: 10.3389/fneur.2017.00605). Fortunately, recent advances, particularly for tinnitus rehabilitation, are encouraging.
Dr. Erbele said the one he is most excited about is Lenire (lenire.com), a U.S. Food and Drug Administration-approved device for treating tinnitus that alters the way the brain experiences phantom sounds by simultaneously providing sound stimuli to the ear and electrical stimuli to the tongue. In one clinical study, the device had a response rate of approximately 92%, with a mean tinnitus improvement of about 28 points on the Tinnitus Handicap Inventory and no device-related serious adverse events (Commun Med [Lond] doi: 10.1038/ s43856-025-00837-3).
“The way this device operates is through biofeedback,” Dr. Erbele said. “It works similarly to cognitive behavioral therapy, which is one of the tools we already have to manage tinnitus.” Coupled with some preliminary work using CI as a suppression tool for severe tinnitus, “there are some exciting advances here to look forward to.”
Dr. Marinelli’s own take on tinnitus focused on two underappreciated comorbid conditions—anxiety and depression. In a recent study of nearly 9,000 patients, those with tinnitus were more likely to suffer from depression (OR = 2.033, 95% CI [1.584; 2.601], P<0.0001), anxiety (OR = 1.841, 95% CI [1.228; 2.728], P=0.0027), or somatic symptom disorders (OR = 2.057, 95% CI [1.799; 2.352], P<0.0001) than individuals without the hearing disorder (J Clin Med. doi: 10.3390/ jcm12031169).
“You have to screen for these psychological conditions when caring for patients with tinnitus,” he said. “Sure, we have effective masking devices and other interventions for the sound component, but the accompanying anxiety and depression can be incredibly debilitating and also need to be addressed.”
For Dr. Adams, successfully treating tinnitus is one of the most satisfying parts of his practice. “When a service member or veteran comes in with hearing loss and is significantly impacted by tinnitus— which, unfortunately, has limited effective treatment options—it can be challenging,” he said. “But when we’re able to properly calibrate the hearing aid and they report noticeable relief and say, ‘I’m good to go,’ it’s incredibly rewarding.”
Looking Ahead
Over the next decade, “we are on the cusp of some incredibly exciting advances, including gene therapy for potentially reversing profound hearing loss—as long as hearing research remains a funding priority,” Dr. Erbele stressed. He added that such advances are not reserved for civilians. In fact, Dr. Erbele said he prides himself on using his research and clinical relationships to ensure that patients in the service “have as much access to cutting-edge clinical trials as anyone else.”
In casting his own eye toward the future, Dr. Marinelli cited expanding access to CIs for veterans. There are myriad reasons why CIs are only implanted in a fraction of all eligible adults in the U.S.—and probably in fewer veterans, he noted. For veterans, one factor is the many comorbid conditions they tend to have, which makes the surgical procedure a challenge, particularly when general anesthesia is used. “But the field is making gains with awake CIs,” he said (J Int Adv Otol. doi: 10.5152/iao.2022.20005). “So hopefully that will move the needle.”
David Bronstein is a freelance medical writer based in New Jersey.
The views expressed herein are those of the authors and do not reflect the official policy or position of Brooke Army Medical Center, the U.S. Army Medical Department, the U.S. Army Office of the Surgeon General, the Department of the Army, the Department of the Air Force, the Department of Defense, the Defense Health Agency, or the U.S. government.
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