Impact of different modifiable factors on hearing function in type 1 and type 2 diabetic subjects. A preliminary study.

INTRODUCTION AND OBJECTIVE Hearing impairment in diabetic subjects is more prevalent than in the general population. Ageing, noise exposure and smoking are known as risk factors of hearing loss. The aim of this study was to assess whether other factors, such as HbA(1c), blood pressure, serum lipids and BMI have an impact on hearing function among relatively young diabetic subjects. MATERIALS AND METHODS 58 patients, 31 with type 1 diabetes and 27 with type 2 diabetes, aged < 45 years, with diabetes duration < 10 years and without overt hearing impairment were included. In all subjects, vital signs, laboratory tests, pure-tone audiometry and trancient-evoked otoacoustic emissions (TEOAE) were evaluated. RESULTS Hearing impairment was revealed in 20 subjects. This group had a lower HDL-cholesterol level compared with normal hearing patients (44.2 mg/dl vs. 57.6 mg/dl, p=0.007). Absence of otoacoustic emissions was diagnosed in 16 subjects. These patients also had a lower HDL-cholesterol level compared with subjects with TEOAE present (45.4 mg/dl vs. 55.2 mg/dl, p=0.018). Hearing threshold was inversely correlated with HDL-cholesterol level, and positively correlated with triglycerides. Patients with HDL-cholesterol level ≥50 mg/dl had lower hearing threshold at frequencies 0.5-12 kHz, as well as higher TEOAE amplitude. Subjects with triglycerides above median had a higher hearing threshold at frequencies 0.5-12 kHz, as well as lower TEOAE amplitude. Patients with elevated BMI (≥25 kg/m(2)) had a higher hearing threshold at frequencies 2-12 kHz, as well as lower TEOAE amplitude. CONCLUSIONS Hearing impairment is frequent among relatively young diabetic subjects. The preseted study reveals that factors like HDL-cholesterol, triglycerides, and BMI may affect hearing function in this group.