Hearing impairment in relation to vitamin D status in type 2 diabetic patients: A cross-sectional study

Objectives: To evaluate the association of serum 25 hydroxy vitamin D (25OHD) and hearing impairment type 2 diabetes mellitus (T2DM) patients. In addition, we aimed to examine whether T2DM-associated hearing impairment is correlated with the severity of diabetes. Methods: The present case-control study recruited adult patients with T2DM and healthy controls. Using pure-tone stimuli, we used an audiometer to assess the hearing thresholds of air conduction in each ear separately. Results: 84 patients and 32 volunteers were included. The serum 25OHD was lower in T2DM patients than in healthy control (12.24±1.3 versus 23.19±5.69, respectively; p<0.001). The prevalence of vitamin D deficiency was 100% in the T2DM group, compared to 25% in the control group (p=0.001). T2DM patients exhibited higher hearing thresholds at all tested frequencies compared to the control group (p<0.001). Diabetic patients with hearing impairment had a significantly lower serum 25OHD than the normal hearing group (11.7±1.2 versus 12.6±1.2 ng/d; p=0.02). The multivariate analysis demonstrated that serum 25OHD level was an independent predictor of hearing loss among diabetic patients (β=-0.605; p=0.041). Conclusions: the present study highlights the potential role of vitamin D deficiency in developing hearing impairment in the setting of T2DM. We found a negative correlation between serum 25OHD level and air conduction thresholds at low-mid and high frequencies amongst patients with T2DM.