Association Between Oxidative Stress Biomarkers and Age-Related Hearing Loss: A Hospital-Based Case–Control Study

Background: Age-related hearing loss (ARHL) is a progressive bilateral sensorineural hearing impairment predominantly affecting high frequencies. Increasing evidence suggests that oxidative stress plays a central role in cochlear degeneration and auditory cell senescence. However, clinical data evaluating systemic oxidative stress biomarkers in ARHL patients remain limited in Iraqi populations. Objective: To assess the association between oxidative stress biomarkers and age-related hearing loss and to evaluate their diagnostic and predictive value. Methods: This hospital-based case–control study was conducted at the Department of Otolaryngology, Al-Kindy Teaching Hospital, Baghdad, between 1st April 2024 and 30th June 2025. A total of 100 participants were enrolled: 50 patients diagnosed with ARHL and 50 age- and sex-matched controls with normal hearing thresholds. All participants underwent pure-tone audiometry (0.5–8 kHz). Hearing severity was classified as mild, moderate, severe, or profound. Serum levels of malondialdehyde (MDA), superoxide dismutase (SOD), and glutathione peroxidase (GPx) were measured using ELISA kits. Statistical analysis included independent t-test, chi-square test, Pearson correlation, logistic regression, and ROC curve analysis. Results: Patients with ARHL demonstrated significantly elevated MDA levels (5.80±1.20 nmol/mL) compared with controls (3.40±0.90 nmol/mL, p < 0.001). Antioxidant enzymes were significantly reduced in cases: SOD (92.50±15.30 vs. 118.60±17.40 U/mL, p < 0.001) and GPx (38.40±6.80 vs. 49.70±7.10 U/L, p < 0.001). MDA showed a strong positive correlation with pure-tone average (r = 0.62, p < 0.001), while SOD (r = −0.58, p < 0.001) and GPx (r = −0.55, p < 0.001) were negatively correlated. Logistic regression identified MDA as an independent predictor of ARHL (Adjusted OR = 3.10, p < 0.001). ROC analysis revealed good diagnostic performance for MDA (AUC = 0.88), SOD (AUC = 0.85), and GPx (AUC = 0.82). Conclusion: Oxidative stress is strongly associated with age-related hearing loss. Elevated lipid peroxidation and reduced antioxidant defense appear to contribute to ARHL severity. MDA, SOD, and GPx may serve as useful biomarkers for risk assessment and early detection of ARHL.