Background: Noise induced hearing loss can only be prevented by eliminating or lowering noise exposure levels. Where the source of the noise can not be eliminated workers have to rely on hearing protective equipment. Several trials have been conducted to study the effectiveness of interventions to influence the wearing of hearing protection and to decrease noise exposure. We aimed to establish whether interventions to increase the wearing of hearing protection are effective.
Objectives: To summarise the evidence for the effectiveness of interventions to enhance the wearing of hearing protection among workers exposed to noise in the workplace.
Search strategy: We searched the Cochrane Ear, Nose and Throat Disorders Group Specialised Register, the Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 2 2005), MEDLINE (1966 to June 2005), EMBASE (1980 to June 2005), NIOSHTIC, CISDOC, CINAHL, LILACS (1982 to June 2005) and Scientific Electronic Library Online. The date of the last search was June 2005.
Selection criteria: Studies were included if they had a randomised design, if they were among noise exposed (> 80 dB(A)) workers or pupils, if there was some kind of intervention to promote the wearing of hearing protection (compared to another intervention or no intervention), and if the outcome measured was the amount of use of hearing protection or a proxy measure thereof.
Data collection and analysis: Two reviewers selected relevant trials, assessed methodological quality and extracted data. There were no cases where the pooling of data was appropriate.
Main results: Two studies were found. One study was a two-phased randomised controlled trial. A computer-based intervention tailored to the risk of an individual worker lasting 30 minutes was not found to be more effective than a video providing general information among workers, around 80% of whom already used hearing protection. The second phase of the trial involved sending a reminder to the home address of participants at 30 days, 90 days or at both 30 and 90 days after the intervention, or no reminder. No significant differences in the mean use of hearing protection were found. A second randomised controlled trial evaluated the effect of a four year school based hearing loss prevention programme among pupils working at their parents farms (N=753) in a cluster randomised controlled trial. The intervention group was twice as likely to wear some kind of hearing protection as the control group that received only minimal intervention. All results are based on self reported use of hearing protection.
Authors' conclusions: Limited evidence does not show whether tailored interventions are more or less effective than general interventions in workers, 80% of whom already use hearing protection. Long lasting school based interventions may increase the use of hearing protection substantially. These results are based on single studies only. Better interventions to enhance the use of hearing protection need to be developed and evaluated in order to increase the prevention of noise induced hearing loss among workers.