Abstract: Objective To compare the differences of distortion product otoacoustic emission (DPOAE) among pre-diabetic patients with normal pure tone threshold and the controls and to investigate the characteristics of hearing loss in pre-diabetic patients. Methods All participants underwent oral glucose tolerance test(OGTT). Thirty pre-diabetic patients with normal pure tone threshold and younger than 60 years were enrolled with 30 age and sex matched controls. Weight, height, and other general information are collected in all subjects. Laboratory tests including hemoglobin A1C, fasting blood glucose, 2-hour postprandial blood glucose, triglyceride, high density lipoprotein cholesterol, low density lipoprotein cholesterol were carried out. Urine albumin-creatinine ratios were calculated. All subjects underwent DPOAE examination. All relevant parameters including DPOAE amplitude were collected. Results DPOAE amplitude at each frequency in the pre-diabetes group was lower than the control group, with statistical significances at 0.7,1, 1.5, 2, 3, 4 kHz in left ear and 1.5, 2, 3, 4, 6 kHz in right ear (P<0.05). Abnormal detection rate at each frequency in the pre-diabetes group was higher than the control group, with statistical significances at 3 kHz(P=0.037). Conclusion When pure tone threshold is normal, the function of outer hair cells of cochlea have been impaired in the pre-diabetes mellitus. The advantage of the right ear was weakened. The distortion product otoacoustic emission is more sensitive than pure tone audiometry.

Key words: pre-diabetes mellitus, pure tone audiometry (PTA), distortion product otoacoustic emissions (DPOAE)