Occupation and 20-year hearing decline: findings from The HUNT Study

BACKGROUND: Studies show that certain occupations are associated with an increased risk of hearing loss. However, many studies are cross-sectional, and the few longitudinal studies are mostly small or focus on only one occupation. AIMS: We aimed to quantify the long-term hearing decline among workers in different occupations and assess whether the change differs between the occupations. METHODS: The study population was 4525 adults who participated in two population-based health studies in Norway, HUNT2 1996–1998 and HUNT4 2017–2019. Linear regression models assessed the association between occupations (clerks as reference) and 20-year hearing decline (hearing thresholds at 3–6 kHz, averaged over both ears) from HUNT2 to HUNT4. Models were adjusted for age, sex, recurrent ear infections, smoking and ear pathology. RESULTS: Among the participants (40% men), the mean age at HUNT2 was 31.2 ± 5.4 years (range 20–39) and the average 20-year hearing decline was 11.3 ± 9.8 dB. Occupations that were associated with larger hearing decline included other craft and related trades workers (3.9 dB, 95% confidence interval [CI] 0.2–7.7) and building frame and related trades workers (3.4 dB, 95% CI 1.3–5.4). Among occupations with larger hearing decline, a higher proportion of the workers reported exposure to noise. CONCLUSIONS: This large longitudinal study shows a larger long-term hearing decline among building frame workers and craft and related trades workers. Differences between occupations were modest, which may indicate successful preventive measures in Norway during the last two decades.