Background: We assessed the auditory function of 94 patients with type 2 diabetes mellitus and 94 age- and sex-matched healthy subjects.
Methods: To study the influence of the clinical characteristics of the disease on the auditory function, after a clinical interview with ophthalmological assessment, subjects were evaluated using pure-tone audiometry, speech audiometry, auditory brainstem responses, the Michigan Diabetic Neuropathy Score and albuminuria. The mean age when diabetes was diagnosed was 42.8 +/- 6.5 years (mean +/- SD) and the time elapsed since diabetes diagnosis was 7.2 +/- 5.4 years.
Results: Forty-eight patients (62%) had HbA1c >8%; diabetic retinopathy was evident in 14 patients (14%) and microalbuminuria was identified in 12 patients. Compared to healthy subjects, diabetic patients showed an increase of the perception threshold at 8000 Hz (p <0.01), higher hearing levels to discriminate at least 90% of 10 monosyllables (p <0.01), and longer latencies of wave V, interwave I-V and interwave III-V (p <0.01). Significant correlation was found between the hearing threshold at 8 KHz and patient age, and the former and the time elapsed since the diabetes was diagnosed (p <0.001).
Conclusions: Patients with type 2 diabetes mellitus can have subclinical hearing loss and impaired auditory brainstem response, independent of peripheral neuropathy, retinopathy or nephropathy.