Association Between HbA1c Level and Hearing Impairment in a Nondiabetic Adult Population

Background: The aim of this study was to investigate whether glycosylated hemoglobin (HbA1c) level in nondiabetic patients is associated with hearing impairment in the general Korean population. Patients and Methods: Data from the Korean National Health and Nutrition Examination Survey 2011-2013 were used in the analyses. Participants were excluded from this study for the following reasons: they could not provide data regarding pure tone audiometry, they had ear disease, they had brain disorders, asymmetric sensory neural hearing loss (HL), or they were younger than 40 years or had diabetes mellitus. Finally, 7449 participants were included in this study. Results: The mean HbA1c levels in the low, middle, and high tertiles were 5.3% +/- 0.2%, 5.7% +/- 0.1%, and 6.1% +/- 0.2%, respectively. The numbers of participants in the low, middle, and high tertiles were 2808, 2509, and 2132, respectively. The low-frequency, mid-frequency, high-frequency, and average hearing thresholds were significantly increased with increasing HbA1c tertile. Linear regression analyses showed that HbA1c level in the nondiabetic participants was associated with components of metabolic syndrome. The mean numbers of metabolic syndrome components in the low, middle, and high HbA1c tertiles were 1.22, 1.53, and 2.02, respectively. The participants in the middle and high HbA1c tertiles had a 1.239- and 1.253-fold increased risk of HL, respectively, compared with those in the low HbA1c tertile. Conclusion: HbA1c level was associated with hearing impairment in the nondiabetic participants of this study. Therefore, the participants with high HbA1c levels should be closely monitored for hearing impairment.