Association between diabetes and high-frequency hearing loss among noise-exposed mineworkers in India: a pooled cross-sectional study

High-frequency hearing loss (HFHL) affects nearly seven in ten mineworkers and represents a substantial yet under-recognised occupational health risk. This condition typically progresses insidiously, impairing communication and compromising workplace safety. Diabetes mellitus (DM), a recognised risk factor for hearing loss in the general population, is understudied in occupational settings. We examined the association between DM and HFHL among noise-exposed mine workers while adjusting for demographic, occupational, and health-related factors. We conducted a cross-sectional study using pooled data from two rounds of periodic medical examinations (PMEs) (2020–2022) among randomly selected, noise-exposed lignite mineworkers (≥ 18 years) in Gujarat, India. Data included demographics, occupational history, anthropometry, blood pressure, and blood tests (haemoglobin, glucose, lipid profile, urea, creatinine), and pure-tone audiometry. Diabetes was defined by self-report or random glucose ≥ 200 mg/dL with symptoms. HFHL was defined as a pure-tone average air-conduction threshold > 25 dB HL across 3, 4, and 6 kHz in the better ear. Group differences were assessed using Welch’s t-tests and chi-square or Fisher’s exact tests. Modified Poisson regression with robust standard errors was used to estimate adjusted prevalence ratios (aPRs) for factors associated with HFHL. Among 335 noise-exposed mine workers, 64 (19%) had diabetes. Mean hearing thresholds were higher among diabetic workers, particularly across 3–6 kHz, corresponding to a higher prevalence of HFHL (89% vs. 65%; p < 0.001), which remained higher after multivariable adjustment (estimated prevalence 80% vs. 67%; adjusted prevalence difference 14% points; p = 0.004). Older age (> 50 years) (aPR 1.61, 95% CI 1.14–2.27; p = 0.006), longer occupational noise exposure (aPR 1.02 per year, 95% CI 1.01–1.04; p < 0.001), and diabetes (aPR 1.21, 95% CI 1.07–1.37; p = 0.003) were independently associated with HFHL. Diabetes was independently associated with a 21% higher prevalence of HFHL among noise-exposed mine workers, beyond traditional risk factors such as age and noise exposure duration. These findings suggest that metabolic health may warrant consideration in occupational hearing conservation. Prospective longitudinal studies are needed to determine whether more frequent periodic medical examinations and HbA1c-based glycaemic monitoring improve hearing outcomes before being considered for routine occupational health practice.