There is no conflict of interest.
Highlights
- The study's objective was to examine the impact of hearing protection device (HPD) fit trainings on health and safety outcomes.
- The study used a randomized controlled trial to assign participants to one of three trainings: experiential HPD, integrated, or current (control group). Using data collected during HPD fit-testing, the authors compared the post-training passing rates between the groups.
- The study found that training method was significantly related to post-training passing rates, with higher passing rates among participants in the experiential HPD and integrated training groups compared to participants in the current training group.
- This study receives a low evidence rating. This means we are not confident that the estimated effects are attributable to the HPD fit trainings; other factors are likely to have contributed.
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Features of the Study
The study was a randomized controlled trial conducted at the U.S. Marine Corps (USMC) Recruit Depot in Parris Island, South Carolina. The USMC training recruits received the standard hearing conservation program orientation as part of their basic training. Recruits completed a baseline hearing protection device (HPD) fit-test where they had to fit a foam earplug to meet a minimum noise threshold (25 decibels). Of the 821 recruits who completed the baseline HPD fit-test, 341 recruits failed the HPD fit-test and required further training.
The authors randomly assigned the 341 recruits to one of three trainings: experiential HPD (eHPD) training, integrated training, or current training (the control condition). The current training consisted of a 30-minute proctored session where recruits watched a military-themed training video within small groups. The eHPD training included a brief one-on-one training session with an expert who described and demonstrated proper use of the earplug followed by the expert inserting the earplug in the recruits’ ears. The integrated training approach included watching the current training video and participating in the eHPD training.
The study collected participant HPD fit-test data (personal noise attenuation ratings) before and immediately after training. The data from 20 recruits were not included in the analysis, resulting in 105 recruits in the eHPD training group, 105 recruits in the integrated training group, and 111 recruits in the current training group. The authors used statistical analyses to compare the post-training passing rates between the groups.
Findings
Health and safety
- The study found that the training method was significantly related to the improvement in noise reduction, where participants who received the eHPD training or integrated training were more successful in properly fitting the HPD in their ears compared to those who received the current training.
Considerations for Interpreting the Findings
Although the authors used a randomized controlled trial, the study had high attrition. In such cases, a study can still receive a moderate causal evidence rating if the analysis controls for differences in background characteristics of the treatment and control groups. However, the authors did not provide demographic information about the groups. It is unknown if they differ in group composition by age, race/ethnicity, or sex. These preexisting differences between the groups—and not the HPD fit trainings—could explain the observed differences in outcomes.
Causal Evidence Rating
Research Guidelines
Review Protocol: Living Systematic Annual Search and Review Protocol
Review Guidelines: Causal Evidence Guidelines