Shadman Nemati - Rhino-sinus, Ear and Skull base Diseases Research Center, Guilan University of Medical Sciences, Rasht, Iran .
Rasool Hassanzadeh - Rhino-sinus, Ear and Skull base Diseases Research Center, Guilan University of Medical Sciences, Rasht, Iran .
Mojtaba Mehrdad - Department of Endocrinology, Razi Hospital, Guilan University of Medical Sciences, Rasht, Iran.
Sahar Sajedi Kia - Department of Otolaryngology, Head and Neck Surgery and Research Center, Amiralmomenin Hospital, Guilan University of Medical Sciences, Rasht, Iran.

Introduction: It seems that diabetes mellitus (DM) can affect the auditory system due to neuropathy, micro-vascular complications, and hearing cell damage during hyperglycemic states. In the current study, we aimed to compare hearing status in patients with type 2 DM (T2DM) according to their blood-sugar control status.   Materials and Methods: This cross-sectional study was carried out in 104 patients with T2DM attending the diabetic clinics of Guilan University of Medical Sciences within a period of 1 year (2014–2015). One group consisted of 52 patients with poor control and the other consisted of patients with moderate-to-good control (according to glycated hemoglobin [HbA1c] level). All subjects underwent pure tone audiometry (PTA) and distortion product otoacoustic emission (DPOAEs) assessments. A hearing threshold higher than 20 dB and a signal-to-noise ratio ≤3 in each frequency were considered abnormal.   Results: In PTA, poorly controlled patients showed more frequent hearing loss compared with the well-controlled group, especially at higher frequencies (8 kHz: 67.3% vs 46.2% [P=0.029]; 10 kHz: 46.2% vs 21.2% [P=0.025]). Also, patients in the poorly controlled group had worse cochlear function according to the DPOAE test (4 kHz: 32.7% vs 17.3% [P= 0.002] and 8 kHz: 70.6% vs 40.4% [P=0.006]).   Conclusion: DM and poor control status of diabetes can affect hearing sensation and cause hearing loss, especially at high frequencies. According to our findings, it seems that diabetic patients with a duration of diabetes > 10 years, diabetic complications, poor control status or comorbidities should undergo both endocrine and audiologic follow-up to prevent greater sensory neural hearing loss.

Diabetes mellitus type 2, Glycated Hemoglobin a, Hearing Loss, Otoacoustic emissions, Sensorineural, Tinnitus, vertigo