Fasting Glucose, Haemoglobin A1C (HbA1c), Blood Lipid, and Triglyceride–Glucose Index Parameters in Relation to Subjective Tinnitus

<b>Objectives:</b> This study aimed to analyse blood glucose and lipid levels in subjective tinnitus compared to healthy controls. <b>Method:</b> A total of 414 patients with subjective tinnitus and 274 healthy participants were enrolled. All participants underwent comprehensive laboratory testing, which included measurements of fasting blood glucose, HbA1c, and blood lipids. <b>Results:</b> The tinnitus group had significantly higher glucose levels than the control group (<i>p</i> = 0.024). Additionally, the HbA1c levels were higher in the tinnitus group (<i>p</i> = 0.006). Tinnitus patients exhibited elevated levels of total cholesterol (<i>p</i> < 0.001), triglycerides (<i>p</i> < 0.001), and LDL (<i>p</i> < 0.001). However, HDL levels showed no significant difference (<i>p</i> = 0.984). Although the triglyceride-glucose index tends to show higher values in the tinnitus group, this difference is statistically insignificant (<i>p</i> = 0.688). ROC indicated that LDL had the highest sensitivity for predicting tinnitus (AUC = 0.620; <i>p</i> < 0.001, 95% CI: 0.573-0.668). Other parameters showed significant results, excluding the triglyceride-glucose index (AUC = 0.514; <i>p</i> = 0.688, 95% CI: 0.443-0.585), which was not a significant predictor. Glucose levels significantly correlate with age (rho = 0.338, <i>p</i> < 0.001) and tinnitus onset (rho = 0.107, <i>p</i> = 0.034). Additionally, age showed a significant correlation with total cholesterol levels (rho = 0.156, <i>p</i> = 0.002) and triglycerides (rho = 0.121, <i>p</i> = 0.020) and tinnitus onset (rho = 0.344, <i>p</i> < 0.001). Logistic regression analysis revealed that the presence of tinnitus was significantly associated with elevated HbA1c levels (<i>p</i> = 0.007) and TG levels (<i>p</i> = 0.001). Furthermore, the occurrence of chronic tinnitus was significantly influenced by elevated glucose levels (<i>p</i> = 0.026). <b>Conclusions:</b> The results showed increased glucose and blood lipid levels in tinnitus. LDL levels exhibited the highest sensitivity in predicting tinnitus. However, the TyG index was not a significant predictor. Given the cross-sectional design of the study, which may limit the results, further longitudinal studies are necessary.