Endocrine Abstracts

Objective: Evidence shows type 1 diabetes leads to vascular damage and neuropathy. The purpose of this study was to perform a systematic review and a meta-analysis to asses the evidence of the effects of type 1 diabetes on hearing function.

Methods: Three different electronic databases were used to identify eligible studies including a manual searching of references. The articles obtained were independently reviewed by two authors using predefined inclusion criteria to identify eligible studies. Meta-analysis was performed on pooled data of hearing loss incidence, PTA thresholds and ABR wave latencies.

Results: Fifteen articles fulfilled the inclusion criteria and passed the quality control evaluation. In most studies, hearing loss (HL) was defined as pure tone greater than 25 dB in the worse ear of at least one frequency. The incidence of HL ranged between 0 and 48% for diabetics, which was higher than in controls (OR=12.43 95% CI 3.09–49.95). The tendency of mean PTA (pure tone audiometry) thresholds were greater in diabetics than in controls for higher frequencies, however the results were not significant. Auditory brainstem response (ABR) latencies were longer in diabetic patients compared to controls. Statistical significance was obtained in wave III and V (Z=3.18, P=0.001 I²=82%; Z=2.55, P=0.01, I²=89% respectively).

Conclusions: Patients with type 1 diabetes have a significantly greater incidence of HL compared to the control group. However, hearing thresholds seems to be not significantly different from control subjects. Mean PTA thresholds were greater at 6000 and 8000 Hz. Despite a trend of higher threshold difference at higher frequencies tested, the mean differences between groups at any frequency were not statistically significant. A significant prolonged ABR of waves III and V latencies in the diabetic group suggest a retro-cochlear involvement in hearing damage in type 1 diabetes.