Occupational noise exposure and asymmetric hearing loss: Results from the HUNT population study in Norway

A large population study with adequate data on confounders is required to determine whether asymmetric hearing loss (AHL) is associated with occupational noise exposure.

We performed a cross-sectional population study in Norway (the Health Investigation in Nord-Trøndelag: HUNT) with 24 183 participants, using pure-tone audiometry and questionnaires. AHL was defined as a difference in hearing threshold between the right and left ears of greater than or equal to 15 dB for the pure-tone average of 0.5 to 2 or 3 to 6 kHz.

The mean age of the participants was 53 years (range, 19-99); 53% were women. The prevalence of AHL in this general Norwegian population was 6% for the 0.5 to 2 kHz range and 15% for 3 to 6 kHz. In unadjusted regression models, subjects reporting prolonged occupational noise exposure to high-level noise sources (N = 1652) had a higher risk of AHL at 3 to 6 kHz than those reporting no prior exposure (odds ratio [OR], 1.98; 95% confidence interval [CI], 1.75-2.25). After adjustment for age and sex, OR was 1.08; (95% CI, 0.95-1.24). After additional adjustment for head trauma, ear infections, blasting or shooting (all associated with AHL), smoking, and diabetes, OR was 1.00 (95% CI, 0.87-1.16). No association between occupational noise and right-ear hearing threshold advantage (left-right ear difference) was observed after adjustment for confounders.

Our study suggests that AHL is relatively common in the general population, especially at the high-frequency range in men and elderly subjects. Our study showed no relation between occupational noise exposure and AHL after confounder adjustment.