Age “Correction” in Hearing Conservation Programs
By: Gregory A. Flamme and Kristy K. Deiters, Contributors
Employers may elect to adjust observed hearing threshold changes as an attempt to account for typical age-related change. However, there is no guarantee that age “correction” correctly represents the influence of age, and adjusted threshold shifts are not interpretable for individuals or small groups—because age-related changes vary widely across people. Further, age adjustments are only valid if they represent longitudinal trends.
Age-adjustment tables currently included in U.S. regulations are based on differences between small groups of people in the 1970s. Thus, employers choosing to age-adjust audiograms are making an implicit assumption that 1970s cross-sectional trends represent current age-related changes. Employers should carefully consider whether this assumption is reasonable.
We have recently developed age-adjustment tables using nationally representative data and validated them using a large occupational hearing conservation database (Flamme et al., 2019). These tables represent current population trends; account for differences in race/ethnicity; span ages 18 to 85 years; and match (within one 5dB audiometric step) median longitudinal changes among male workers through 30 years on the job.
Shallower cross-sectional trends were observed for people identifying with non-Hispanic Black race/ethnicity, and overall trends imply substantially less age-related change in hearing thresholds than is assumed in current U.S. regulations [see chart]. Employers applying 1970s-based age adjustments will substantially overestimate current age-related effects, and threshold shifts due to other factors (e.g., occupational/non-occupational exposure, disease) would be missed.
Regulations have not been modified to include recent adjustment tables, so employers must either (1) use tables that do not represent current trends; or (2) forego age adjustment. NIOSH has advised against using age “corrections” for decades and recent findings support that advice.
[Gregory A. Flamme and Kristy K. Deiters, are with Stephenson & Stephenson Research & Consulting Researchers are also and National Hearing Conservation Association (NHCA) Experts. Visit NHCA at: https://www.hearingconservation.org/]