Neuropathy is frequently a late complication of diabetes mellitus. Auditory neuropathy and microangiopathy of inner ear are the possible causes of hearing loss in diabetics. To study the correlation between glycaemic control and hearing threshold in patients with type 2 diabetes mellitus and to determine the differences of hearing threshold between groups treated with different modality. This single blind randomized controlled study was performed at the Department of Medicine and Department of Otorhinolaryngology, Hospital Universiti Kebangsaan Malaysia (UKM) between 1st May 2003 and 31st September 2004. This study was approved by Research Ethics Committee (code number FF-137). Subjects were randomized into two groups. Group 1 were patients treated with conventional oral hypoglycemic agents. The patients in group 2 were those treated with insulin injection. The subjects were seen 4 weekly for 3 months. Audiometric test were performed in all subjects at each visit. Blood were taken for fasting blood glucose, Hb1Ac, and fructosamine at every visit to determine the glycaemic controls of the subject. They were 11 patients (22 ears) treated with oral hypoglycemic agents and 17 patients treated (34 ears) with subcutaneous insulin. There is no significant difference between mean pure tone threshold before and after treatment at all frequencies in both groups. There is also no significance different in fasting glucose level and fructosamine. However, there is significant difference HbA1c levels between the two groups after treatment (P < 0.05). This study has shown that glycaemic control does not have significant impact on hearing. The hearing threshold is neither affected by insulin treatment nor by the glycaemic control.
Keywords: Diabetes mellitus; Fructosamine; Glycemic control; Hearing loss; Insulin.