Risk Of Hearing Impairment Among Type 2 Diabetic Adults

Objective:The study was to examine the prevalence of hearing impairment in Type 2 Diabetes Mellitus(T2DM), the risk factors of DM-related hearing loss and the application of audiological examination method in diabetes hearing impairment. And to investigate the effect of glycemic control and lipoic acid on diabetic hearing impairment. Design and Methods:160 diabetics and 42 healthy subjects participated in the study. Participantswere investigated by tympanogram, pure-tone audiometry(PTA), distortion product otoacoustic emissions(DPOAEs) and auditory brainstem responses(ABRs). All individuals were interviewed and completed clinical examination.Results: Character of Diabetic- related Hearing Impairment: Significantly difference was observed in PTA thresholds of diabetic subjects at 0.5, 1, 2, 4, 6, and 8 k Hz compared with controls(P<0.05). Diabetic patients significantly increased the latencies V and the interwave latencies III-V and I-V of ABR compared with control groups(P<0.05). DPOAE amplitude was reduced in diabetic patients at all frequencies of both ears(P<0.001). The comparison of DPOAE by hearing status showed significant differences at all frequencies of both ears, except 0.75 k Hz of right ear. Michigan Neuropathy Screening Instrument, vibration perception threshold, and Semmes-Weinstein Monofilament were associated with decrease in hearing thresholds. Diabetic nephropathy, e GFR, blood urea nitrogen, diabetic neuropathy and A1 C were related to hearing in PTA and/or DPOAE.Correlation among PTA, ABR and DPOAE: An abnormal increase of ABR latencies was present in 84.72%(n=61) diabetes subjects. Only 44 of 61 impaired-ABR subjects(72.13%) were observed with hearing loss. Absence of DPOAE in diabetes was found in 23 subjects bilateral or unilateral(36.51%). The association of hearing impairment with impaired cochlear response was noted in 21 of the 23 subjects. The results indicate that ABR and DPOAE contribute to early detect diabetic hearing impairment.Effect of glycemic control and lipoic acid on diabetic hearing impairment: The control group with 14 diabetes mellitus received short-term intensive insulin therapy. 24 diabetes mellitus received intravenous drip of lipoic acid(600mg/d) for 10 to 14 days. The mean PTA thresholds were increased at any frequencies after glycemic control, and the significant difference was observed in 0.25, 0.5 k Hz of left ear and 4 k Hz of right ear. The mean PTA thresholds were lower after short-term intensive insulin therapy, however,the difference did not reach significance.Conclusion: The present study suggests that hearing loss are common in diabetic subjects, involved both cochlear and retrocochlear parts. Diabetic nephropathy, e GFR, blood urea nitrogen or diabetic neuropathy may play an important role in diabetic hearing impairment. In addition, we suggested that the ABR and DPOAE test would be considered as supplementary procedures to monitor early dysfunction in auditory pathway and neurological measurements could be used to predictive the hearing loss in diabetic patients. Lipoic acid could improve diabetic hearing impairment.