Is this STS work-related? ISO 1999 predictions as an adjunct to clinical judgment

Area of Science:

• Occupational audiology
• Epidemiology of hearing loss
• Industrial hygiene

Background:

• Physicians and audiologists frequently assess if standard threshold shifts (STSs) are work-related.
• Epidemiological data is crucial for informing these work-relatedness decisions.

Purpose of the Study:

• To present predictions from the ISO 1999 model for age-related and noise-induced hearing threshold shifts.
• To provide tools (tables, graphs, spreadsheet calculator) for estimating hearing thresholds based on age, sex, and noise exposure.
• To illustrate how these predictions can differentiate contributions of aging and occupational noise to STSs.

Main Methods:

• Utilized the ISO 1999 model to estimate age-related hearing thresholds based on age and sex.
• Applied the ISO 1999 model to estimate noise-induced threshold shifts based on noise level and duration.
• Calculated final hearing thresholds by summing expected age-related and noise-induced shifts for a given individual's profile.

Main Results:

• Standard threshold shifts (STSs) in early careers, particularly with high noise exposure, are predominantly noise-induced.
• After approximately ten years of occupational noise exposure, the majority of STSs become primarily attributed to age-related hearing decline.

Conclusions:

• The ISO 1999 model provides valuable estimates of age and noise contributions to hearing shifts.
• These estimates can effectively supplement clinical judgment when evaluating the work-relatedness of STSs in employees.
• Worker's age, sex, and occupational noise exposure history are key inputs for the ISO 1999 model.