Subclinical Cochlear Dysfunction in Tinnitus Patients with Normal Hearing: Association with Tinnitus Severity

Background: Tinnitus with normal hearing may be associated with cochlear dysfunction undetectable by conventional audiometry. Distortion product otoacoustic emissions (DPOAEs) can identify these early cochlear changes. Aim: The study aimed to evaluate DPOAE amplitudes in tinnitus patients with normal hearing and to assess their association with tinnitus severity. Methods: This case–control study included 80 participants (40 tinnitus patients and 40 controls) recruited through convenience sampling over a 5-month period (November 2025–March 2026). Eligible participants were adults aged 18–45 years with normal hearing and middle-ear function. Individuals with otologic or systemic disorder that could affect auditory function were excluded. All participants underwent otoscopic examination, tympanometry, pure-tone audiometry, and (DPOAEs). Tinnitus severity was assessed using the tinnitus handicap inventory. Results: Tinnitus patients demonstrated significantly lower DPOAE amplitudes compared to controls at all frequencies ( P < 0.05). Mean amplitudes ranged from 2.76 to −7.61 dB SPL in the tinnitus group compared with 7.03–0.28 dB SPL in controls. Moderate-to-severe tinnitus was associated with significantly reduced DPOAE amplitudes between 3200 and 4800 Hz. Tinnitus severity was significantly associated with duration, pattern, and laterality ( P < 0.05). No significant association was found between sound quality and tinnitus severity. Conclusions: In normal hearing, individual’s tinnitus is associated with reduced DPOAE responses, indicating possible subclinical cochlear dysfunction. Tinnitus severity is related to clinical characteristics and selective frequency-specific cochlear changes; therefore, DPOAEs may serve as a useful adjunct in evaluating cochlear involvement in tinnitus.