Effectiveness of the Healthy Hearing Promoting Program (HHPP) among workers in large-scale industries: A randomized...

Noise-induced hearing loss remains a significant occupational health concern in industrial settings. Adherence to protective behaviors among workers remains suboptimal, leaving them at continued risk of hearing impairment. Strengthening hearing health promotion is therefore essential.

To evaluate the effectiveness of the Healthy Hearing Promoting Program in promoting noise hazard protection behavior and maintaining hearing capacity among workers in large-scale industries.

This single-blind parallel-group randomized controlled trial included 66 industrial workers from two large-scale factories in central Thailand, randomly assigned to an experimental group (n = 33) and a control group (n = 33). The control group continued routine occupational practices based on existing factory safety policies. Data were collected between December 2023 and July 2024. Noise hazard protection behavior was assessed at baseline, Week 10, and Week 14, while hearing capacity was evaluated at Week 34 (26 weeks after intervention completion). Statistical analyses were conducted using mixed-design ANOVA and Fisher's exact test.

There were no significant differences in baseline data between groups. The experimental group had significantly higher noise hazard protection behavior scores than the control group (F (1,64) = 41.67, p < 0.001, partial η² = 0.394), with significant changes over time (F(2,128) = 48.02, p < 0.001, partial η² = 0.429) and a significant group-time interaction (F(2,128) = 24.12, p < 0.001, partial η² = 0.274). Between-group mean differences in protection behavior scores were 5.91 points (95% CI: 3.6, 8.2) at Week 10 and 7.39 points (95% CI: 5.3, 9.5) at Week 14. All participants in the experimental group demonstrated hearing thresholds within the normal range across all tested frequencies at follow-up. A small proportion of control group participants exhibited abnormal thresholds at frequencies between 500 and 4000 Hz.

The program significantly improved noise hazard protection behaviors but no significant between-group differences in hearing capacity were demonstrated. The findings provide preliminary evidence to support occupational health nurses in developing and implementing theory-driven, multilevel hearing conservation interventions aimed at improving noise hazard protection behaviors among workers in large-scale industries.

Thai Clinical Trials Registry (TCTR20251128006).