Listen Up! From the NHCA Experts…

Age Adjustments in Audiometric Monitoring

Routine audiometric monitoring is an important step in hearing loss prevention programs, allowing for the assessment of hearing changes across time. Optional age adjustments have been allowed by subtracting out expected “age” effects. Whether to apply age adjustments at the individual level (Figure 1), and which ones to use, has important implications for detecting changes in hearing that may be due to occupational noise exposure.

Figure 1. Simulation of audiometric thresholds for 1,000 individuals across time. Applying the mean (dashed line) age adjustment will under- or overrepresent “age” changes most of the time. The blue and red lines represent two individuals’ changes across time.

The age adjustment tables in Occupational Safety and Health Administration (OSHA) 1910.95 Appendix F were based on a 1970’s National Institute for Occupational Safety and Health (NIOSH) study using a small sample of primarily Caucasian participants, possibly with significant occupational/military noise exposure. The tables extend only to age 60.

Since then, hearing has improved in the U.S. population, and older and more diverse workforces are common. Updated age adjustment tables were recently developed using data representing the current U.S. population (National Health and Nutrition Examination Survey [NHANES] data); extend to ages 85+; and account for known differences in race/ethnicity. These tables were validated against longitudinal data and match hearing results of New York Fire Department (FDNY) and EMS workers for up to 35 years of audiometric monitoring (Figure 2).

Figure 2. Top panel: Longitudinal validation using 35 years of data from FDNY firefighters and EMS workers against the NHANES age adjustment tables (Flamme et al, 2019). Results match longitudinal mean hearing within one audiometric step at all frequencies up to 35 years of service. Bottom panel: The number of audiometric tests conducted across years of service.

Best practice indicates age adjustments should not be applied to hearing thresholds, as it reduces the ability to detect smaller changes in hearing before significant change has occurred. If using age adjustments, OSHA recommends using their updated tables.*

What can you do?

• If stopping age adjustment is not an option, consider a hybrid approach to monitoring hearing, wherein internal action (HPD retraining, fit testing, etc.) is taken based on unadjusted thresholds and external action (OSHA 300 log) is taken based on adjusted thresholds.
• Watch for OSHA guidance and letters of interpretation.
• Encourage age adjustment software developers to update software based on the new tables.*

*Updated OSHA tables can be found at: https://www.tandfonline.com/doi/suppl/10.1080/14992027.2019.1698068?scroll=top

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