Randomized trial of a hearing conservation intervention for rural students: long-term outcomes

We had the rare opportunity to conduct a cluster-randomized controlled trial to observe the long-term (16-year) effects of a well-designed hearing conservation intervention for rural high school students. This trial assessed whether the intervention resulted in (1) reduced prevalence of noise-induced hearing loss (NIHL) assessed clinically and/or (2) sustained use of hearing protection devices.

In 1992-1996, 34 rural Wisconsin schools were recruited and 17 were assigned randomly to receive a comprehensive, 3-year, hearing conservation intervention. In 2009-2010, extensive efforts were made to find and contact all students who completed the original trial. Participants in the 16-year follow-up study completed an exposure history questionnaire and a clinical audiometric examination. Rates of NIHL and use of hearing protection were compared.

We recruited 392 participants from the original trial, 200 (53%) from the intervention group and 192 (51%) from the control group. Among participants with exposure to agricultural noise, the intervention group reported significantly greater use of hearing protection compared with the control group (25.9% vs 19.6%; P = .015). The intervention group also reported significantly greater use of hearing protection for shooting guns (56.2% vs 41.6%; P = .029), but the groups reported similar uses of protection in other contexts. There was no significant difference between groups with respect to objective measures of NIHL.

This novel trial provides objective evidence that a comprehensive educational intervention by itself may be of limited effectiveness in preventing NIHL in a young rural population.