The influence of hearing impairment on sleep quality among workers exposed to harmful noise.

OBJECTIVE: To assess connections between sleeping quality and hearing impairment due to prolonged exposure to industrial noise.

DESIGN: Observational cross-sectional study.

SETTING: Occupational clinic of the Clalit Health Services in Israel.

PARTICIPANTS: 298 male volunteers occupationally exposed to harmful noise, who had an audiometric examination performed by an occupational nurse as a part of the national workers health supervision programs.

MEASUREMENTS AND RESULTS: The participants underwent an audiometric testing, and their sleep quality was measured by a validated Mini Sleep Questionnaire (MSQ). Participants with hearing loss greater than 25 dBA in the range of 1000-4000 Hz were defined as the research group (n = 99) and were compared to those with no hearing impairment (n = 199). Sleeping disorders were age related (30% higher MSQ score among workers above 50 years, P = 0.003). Tinnitus was the highest sleep disturbing factor, with 75% higher score among those affected, P = 0.001. In multiple linear regression analysis, tinnitus was the leading sleep-disturbing factor (regression coefficient B = 8.66, P < 0.001) followed by hearing impairment (regression coefficient B = 2.42, P = 0.084), adjusted for age (or years of exposure) and coffee drinking. A part of the MSQ, related to insomnia, was further evaluated using logistic regression models. Tinnitus was again the leading sleep disturbing factor [OR = 11.91; CI95% (1.56-91.2)], followed by hearing impairment [OR = 3.051; CI95% (1.18-7.86)].

CONCLUSION: Although tinnitus was the main sleep disrupting factor, hearing impairment among workers occupationally exposed to harmful noise, independently contributed to sleep impairment, especially to insomnia, regardless of age and years of exposure.