DPOAEs AND SUSCEPTIBILITY TO TINNITUS IN NORMAL HEARING SUBJECTS EXPOSED TO NOISE

Job A (1), Raynal M (2), Kossowski M (2).

(1) CRSSA centre de recherches du service de santé des armées, France; (2) Hopital d'instruction des Armées de Percy, France.

We investigated potential markers of susceptibility to tinnitus in a population of normal hearing young pilots aged 25-35 years and with 8 ± 5 years of aircraft noise exposure. A sample of 316 pilots were interviewed about their tinnitus status and were tested for hearing thresholds (audiograms) and distortion products otoacoustic emissions (DPOAE-grams). There was no subject with permanent tinnitus. 23 % reported to perceive occasionally tinnitus after flight missions and 77 % reported never having experienced tinnitus after flight missions. General discomfort in the ears to noise was higher in the occasional tinnitus group (15 % vs  6%). The major finding was that difference of susceptibility to tinnitus in normal hearing subjects exposed to noise on a daily basis seemed to be clearly related to lower DPOAEs, bilaterally, in the 1500-2800 kHz range. However, no difference could be observed between groups, on audiograms at the 2 kHz frequency range. This study provided evidence of outer hair cell dysfunctions in normal hearing subjects exposed to noise, susceptible to tinnitus. Hypersensitivity to noise and DPOAEs decreases in a non noise-specific frequency range supported the idea of another alteration mechanism than noise itself. This point was discussed in the light of recent publications.

 

E-mail: ajob.crssa@gmail.com