Diabetes-related changes in auditory brainstem responses.

Objectives/hypothesis: Determine effects on auditory brainstem response (ABR) of diabetes mellitus (DM) severity.

Study Design: A cross-sectional study investigating DM severity and ABR in military Veteran subjects with (166) and without (138) DM and with no more than moderate hearing loss.

Methods: Subjects were classified by three age tertiles (<50, 50-56, and 57+). DM severity was classified as insulin-dependent (IDDM), non-insulin-dependent (NIDDM), or no DM. Other DM measures included serum glucose, HbA1c, and several DM-related complications. ABR measures included wave I, III, and V latencies; I-III, III-V, and I-V latency intervals; and wave V amplitude; for each ear at three repetition rates (11, 51, and 71 clicks/second), and both polarities. Outcomes were stratified by age tertile and adjusted for pure tone threshold at 3 kHz. Repeated measures multivariate analysis of covariance modeled the ABR response at each repetition rate for DM severity (main effect) and hearing at 3 kHz (covariate). Modeled contrasts between ABR variables in subjects with and without DM were examined.

Results: Significant differences existed between no DM and IDDM groups in the younger tertile only. Adjusting for threshold at 3 kHz had minimal effect. Self-reported noise exposure was not related to ABR differences, but HbA1c and poor circulation were.

Conclusions: IDDM is associated with an increased wave V latency, wave I-V interval, and reduced wave V amplitude among Veterans under 50 years. Results were related to several DM complications.