Sensorineural Hearing Loss and Type II Diabetes Mellitus

Abstract

Background: The association between Hearing loss and diabetes, first mentioned by Jardao in 1857, had been under continuous research since then; giving both positive and negative results. This study aims to explore the relationship of hearing loss with type II DM and also to evaluate the impact of glycemic control over degree of hearing loss. Methods: 92 patients with type II DM were enrolled in this study, audiometrically evaluated and compared with equal number of age and sex matched non-diabetic controls. Apart from audiological tests, haematological tests like FBS, PPBS, HbA1c, serum creatinine and cholesterol were carried out to assess glycemic control. Results: It was observed that 31 (34%) of the diabetic patients had mild to moderate sensorineural hearing loss, while only 12 (13%) of the control group suffered from the same, which is statistically significant (p<0.05). Among these 31 patients, 19 (61%) patients had uncontrolled diabetes (HbA1c >8.5) and 12 (39%) had higher creatinine levels (>2.5 mg/dl). Higher frequencies (4 and 8 kHz) were found to be affected more, both in case and control groups. Low stapedial reflex thresholds were observed in 14% patients of case group and 5.4% of the controls. Speech discrimination scores were not significantly different. Otoacoustic emission showed outer hair cell dysfunction in 85% cases and 66% controls. Conclusions: There is a strong correlation between diabetes mellitus and hearing threshold levels especially at higher frequencies. Long duration and uncontrolled diabetes has more implications over hearing threshold. Since the pattern of hearing loss in diabetes and presbycusis is similar, it may be said that hearing level with ageing is significantly impaired earlier in diabetic patients as compared to general population.