Effects of Type 2 Diabetes on Otoacoustic Emissions and the Medial Olivocochlear Reflex

OBJECTIVE: To demonstrate if cochleopathy in patients with type 2 diabetes with normal audiometric hearing threshold can be detected with otoacoustic emissions or medial olivocochlear (MOC) reflex measurements. STUDY DESIGN: Cross-sectional study. SETTING: Tertiary university teaching hospital. METHODS: The study involved 40 type 2 diabetic patients and 24 healthy volunteers. All participants who showed normal otoscopic findings, hearing thresholds, and acoustic admittance were included. Cochlear activity of participants was evaluated by means of distortion product otoacoustic emissions (DPOAEs) and transient otoacoustic emissions (TOAEs). The MOC reflex was evoked with contralateral acoustic stimulation and recorded with DPOAEs and TOAEs. RESULT: A comparison of DPOAE and TOAE levels with a t test between patient and control groups revealed no significant difference (P > .05). A comparison of the MOC reflex response between the 2 groups also revealed no statistically significant difference (P > .05). CONCLUSION: Although decreased OAE amplitude levels were found in diabetic patients, there was no statistically significant difference in OAEs and MOC reflex. Additional studies are needed to evaluate the role of OAEs and MOC reflex in normal-hearing patients with diabetes.