Hearing loss in military aviation and other trades: investigation of prevalence and risk factors.

INTRODUCTION

Continuous increase in the cost of claims for noise-induced hearing loss in Canadian Forces personnel prompted a review of hearing conservation practices. Investigations comprised retrospective analyses of hearing test results and a prospective survey of risk factors for hearing loss.

METHOD

There were 1057 individuals working in 107 air, land, and sea trades who contributed their current and first hearing test results. Subjects completed a 64-item questionnaire relating to demographics, occupational and non-occupational noise exposure history, training in and use of hearing protection, and non-noise risk factors, including head injury, ear disease, medications, and solvent exposure. Subject recruitment, hearing assessment, and questionnaire distribution were carried out by military personnel. Apparatus and protocols for hearing testing conformed to current clinical practice.

RESULTS

Prevalence of moderate to severe hearing loss progressed with age, with hearing thresholds in those over 45 yr ranging broadly from normal to over 70 dB HL. Unprotected exposure to noise and solvents appeared to be the likely determinates of adverse outcome. Head injury, ear disease, and the use of ototoxic medications had minimal impact. The data for individuals in 17 selected trades in the 3 environments modeled that of the total sample.

DISCUSSION

Responses to the questionnaire suggested that training on noise hazard and selection and use of hearing protection were inadequate. Hearing protection was reported to be incompatible with other gear, uncomfortable, and an impediment to communication. Approaches for upgrading hearing conservation strategies, including the creation of end-user focus groups, were considered.