Support for the central theory of tinnitus generation: a military epidemiological study.

Tinnitus is poorly reflected by audiometric (cochlear) data, indicating that central nervous system (CNS) components are involved in its development. This study aimed to provide support for the neurophysiological theory of tinnitus as a result of combined peripheral and central nervous dysfunctions. Our main findings were the sudden. significant, stepwise increase in tinnitus after 10 years of service, as opposed to the almost linear increase in noise-induced hearing loss (NIHL) with age. Furthermore, the absence of a correlation between the incidence of tinnitus and the severity of tinnitus was linked to the NIHL. We suggest that, in tinnitus, the central screening apparatus which normally inhibits conscious awareness of irrelevant, spurious and non-informative internal and external noise shows a possibly fatigue- or age-related deterioration over time. Further support was provided by low blood levels of vitamin B1 and B12. which are essential to CNS function.