Overall versus individual changes for otoacoustic emissions and audiometry in a noise-exposed cohort

Abstract

Objective: For a noise-exposed group of workers, group-averaged and individual changes were compared for pure-tone audiometry, transient-evoked otoacoustic emissions (TEOAEs), and distortion product otoacoustic emissions (DPOAEs) in order to see if they exhibit the same pattern in time. Design: Baseline and 17-months follow-up hearing status was examined with pure-tone audiometry, TEOAEs, and DPOAEs. Study sample: A total of 233 noise-exposed employees were measured, while 60 subjects from this group contributed to test-retest reliability measures. Results: Group-averaged changes and individual shifts followed similar patterns: decreases for audiometry at 6–8 kHz and DPOAE at 1.5 kHz, and enhancements for DPOAE at 3 kHz. TEOAEs showed an overall deterioration while both individual deteriorations and enhancements were larger than chance. DPOAE at 6 kHz showed the largest group-averaged change, while the number of individual shifts was not significant. There were no clear relations between changes in audiometry and changes in OAE. Conclusion: Significant individual OAE changes do not necessarily follow the same pattern as the group-averaged results. This limits the applicability of OAE testing for the monitoring of individual subjects. Furthermore, hearing deterioration might manifest itself in a local enhancement of otoacoustic emissions and not only in the form of decreases in amplitude.

Key Words::

• Otoacoustic emissions (OAEs)
• noise-induced hearing loss (NIHL)
• monitoring
• hearing conservation
• audiogram
• significant threshold shift
• significant emission shift

Acknowledgements

Thanks to Miranda Neerings (AMC) for all her work in the data collection. Also thanks to the people from Hearing Coach, ArboNed/Keurcompany, ‘De Telegraaf’, and at the AMC who have contributed in one way or another to this paper. R Development Core Team (2007). R: A language and environment for statistical computing. R Foundation for Statistical Computing, Vienna, Austria. ISBN 3 - 900051-07 - 0, URL http://www.R-project.org.

Declaration of interests: The authors report no conflict of interest. The authors alone are responsible for the content and the writing of the paper.