FUNCTIONAL IMPAIRMENT IN SERVICE MEMBERS WITH NORMAL AUDIOMETRIC THRESHOLDS

Military service is more hazardous to hearing than almost any other occupation, and both the line and medical components of the Department of Defense (DoD) have a responsibility to protect Service members from the harmful effects of noise exposure. Despite the best efforts of a comprehensive DoD-wide hearing conservation program, hearing loss and tinnitus continue to be the most frequent permanent injuries in the military; nearly 30% of Service members experience a permanent threshold shift and just over 30% report tinnitus. These problems propagate to our Veteran population, resulting in almost 1.5 million Veterans receiving compensation for hearing loss and tinnitus. Of further concern is the increasing incidence of Service members reporting hearing difficulty and/or tinnitus in the presence of normal hearing. These factors could have a significant impact on readiness and resilience in the active duty population.

The goal of this research effort is to advance our understanding of the etiology and implications of noise- and blast-related hearing damage in our active duty population with normal or near-normal audiograms, and obtain normative data for tests that could be used to efficiently assess these problems in DoD Audiology Clinics. This will be accomplished by three studies. The first study will be a direct evaluation of the relationship between objectively measured noise dosimetry and subjective noise surveys. These data will be used to improve the ability to obtain reliable self-reports of noise exposure. In the second study, auditory tests that are sensitive to objective differences in performance among Service members with normal or near-normal thresholds and varying levels of noise and blast exposure will be identified, to establish normative data in those tests that will facilitate their direct transition to clinical use. Finally, auditory and functional tests that are sensitive to differences in performance among Service members with normal or near-normal thresholds and various levels of bothersome and non-bothersome tinnitus will be identified, and normative data will be established to facilitate direct transition to clinical use. It is expected that clinical norms will be available in Year 2 of this project. The availability of clinical norms should facilitate assessment and diagnosis of hearing and tinnitus complaints.