Research in Medicine

Background : Noise-induced hearing loss is among the most common cause of occupational-related hearing loss. Nowadays, noise-induced hearing loss is a disastrous event of industrial world that may influence all races, ethnics and age groups.

 Methods : This cross sectional study was performed on 100 workers exposed to noisy environment (greater 85db) in Azmayesh factory. Having excluded all confounding variables, sixty 25-64 year-old workers were included and a thorough physical examination and desired laboratory tests were instituted. PTA was achieved 48 hours after occupational resting for both ears.

 Results : Noise with the frequency of 4000Hz could impair hearing function since only 48.3% of workers had normal hearing parameters. This impairment may be more significant as the duration of exposure increased. Meanwhile, 72.2% of workers who have been exposed less than 10 years to noisy environment had normal hearing function, while after 20 years of exposure this figure was as low as 33.3%. Age was inversely correlated with hearing function. As 60% of 25-34, 76.5% of 35-44, 37.5% of 45-54, and 42.9% of 55-64 year-old workers had normal hearing function.

Conclusion : Hearing loss is a frequent complication of noisy environment. All industrial factories are strongly recommended to observe protective facilities if their workers are exposed to noisy environment of greater than 85db. Periodic hearing assessment is also suggested for susceptible workers.