Soldiers sent to battle zones are over 50 times more likely to suffer noise-induced hearing loss (NIHL) than soldiers who do not deploy, according to research published in the December 2005 issue of American Journal of Audiology (AJA). The study, led by Thomas M. Helfer, Nikki N. Jordan, and Robyn B Lee of the U.S. Army Center for Health Promotion and Preventive Medicine, examined the cases of 806 U.S. soldiers diagnosed with NIHL.
The research was publicized in the Feb. 21 edition of the Cleveland Plain Dealer and received feature coverage in the Feb. 22 edition of the Seattle Times.
Thousands of U.S. soldiers sent to Iraq have suffered NIHL due to a lack of education about hearing protection, a reduced force of military audiologists, and a lack of monitoring for threshold shifts, the research states.
Of these soldiers, 5.6% suffered acoustic trauma from a single loud noise, such as a bomb blast. Another 1.6% had broken eardrums, which often heal, but leave soldiers vulnerable to ear infections in unsanitary battlefield conditions. About 29% had a permanent threshold shift, and in 15.8%, the hearing loss was considered significant enough to limit or disqualify a soldier from duty according to military standards. Most visits for eardrum perforation or a permanent threshold shift occurred in April to June 2003, a period that coincided with the heaviest combat operations and blast injuries during Operation Iraqi Freedom.
"These are not just mild hearing losses that you and I might have from listening to music, or from aging," said Brenda Lonsbury-Martin, ASHA chief staff officer for science and research. "These are pretty severe hearing losses that will impact your life."
Many of these injuries could have easily been prevented. However, there was an inadequate supply of earplugs for all soldiers, and a failure to provide unit commanders with information about troops having adequate hearing protection and pre-deployment baseline audiograms.
The Army is also operating with a reduced force of audiologists-about half of the approximately 70 audiologists it employed in the 1990s-and currently only one audiologist is deployed in Iraq at any given time, said Helfer.
The research followed an Institute of Medicine (IOM) study that criticized the military's efforts to protect service members' hearing since World War II, when many veterans returned home with hearing loss. The IOM study, which was requested by Congress, noted that service members are often exposed to high-level noise over a prolonged period. Yet the IOM found that between the early 1980s and 2002, only 30% of Navy or Marine Corps personnel were given hearing tests at the beginning and end of service. For Army and Air Force personnel, only 12% were given hearing tests.
Helfer said a greater effort is under way to test the hearing of all new soldiers in basic combat training and those preparing for deployment. He said the Army in recent months has broadened its distribution of ear protection and increased training.
It is important to note that some NIHL is unavoidable despite use of hearing protection and other measures, Helfer said in the study. "This is because some exposures…are so extreme that they will exceed the protective capability of hearing protective devices. In addition, skull transmission of intense noise, the element of surprise, and the coeffects of inhaled toxins such as carbon monoxide in conjunction with noise can affect hearing loss outcomes."
NIHL is the third most common disability among veterans, the IOM report said, noting that the Department of Veterans Affairs pays $805 million in compensation annually to veterans whose primary impairment is hearing loss or tinnitus.