Objectives: Metabolic syndrome (MetS) is a complex metabolic disease characterized by central obesity, impaired glucose metabolism, dyslipidemia, arterial hypertension, insulin resistance, and high-sensitivity C-reactive protein. Some factors associated with MetS may increase the risk of hearing loss; we hypothesized that cases with MetS would have an acceleration of hearing loss compared to those without MetS. The purpose of this study was to analyze the association of insulin resistance and MetS with hearing impairments and to prove our hypothesis.
Methods: This study was a retrospective study performed in a medical center. The subjects in this study were the employees from a single company. Homeostasis Model Assessment for Insulin Resistance (HOMA-IR) was used as the index of insulin resistance. The pure tone audiometric data of a 10-year-period were retrieved from the computerized database. The 10-year shifts of average hearing levels, including conventional frequencies (0.5, 1, 2 kHz) and high frequencies (4, 6, 8 kHz), were used to analyze the correlations with HOMA-IR and MetS. Linear regressions were used to estimate the coefficients of age, sex, HOMA-IR, and metabolic syndrome to hearing level shifts. The level of statistical significance was set as p<0.05.
Results: Data from169 cases, including 162 men and 7 women, were analyzed in this study. Age was the most relevant factor to hearing loss. After adjusting for age and sex, HOMA-IR was found to be associated with a high-frequency hearing level shift (coefficients=0.156, p=0.035), while HOMA-IR was not found to be significantly associated with conventional frequency hearing loss. However, MetS was not found to be significantly associated with either conventional or high frequency hearing level shifts. Conclusions: Insulin resistance is associated with the acceleration of age-related hearing loss, while MetS is not shown to increase the risk of hearing loss. Based on the findings of this study, agents that help lower insulin resistance may play a role in the deceleration of age-related hearing impairment.