DPOAEs in young normal-hearing subjects with histories of otitis media: evidence of sub-clinical impairments.

To investigate the origin of the susceptibility to noise in subjects with histories of otitis media (OM), we assessed early sub-clinical impairments in normally hearing subjects with a history of OM using distortion product otoacoustic emissions (DPOAEs). DPOAEs of 213 normal-hearing subjects aged 18-24 years were obtained and comparisons of DPOAE levels in several groups as a function of OM past infections were tested by ANOVA. A main finding was that young normal-hearing subjects with a history of OM had significantly lower DPOAEs over all octaves tested compared to normal-hearing subjects without antecedent of OM. The mean difference was 3.5+/-1.1 dB in the 2-4 kHz zone, which was especially marked in subjects (n=21) that had undergone a myringotomy (6.6+/-1.5 dB) in the 4 kHz zone. The level of impairment seemed to depend on the severity of the past infection as characterised by the importance and the duration of the infectious effusions.