ABSTRACT
This study investigated the effect of chronic workplace exposure to excessive noise on sleep quality. It involved 40 male workers aged 33 to 50 years, 20 of whom had been exposed to environmental workplace noise levels of 85 dB or more on 40-hour-a-week jobs. Another 20 workers who were not exposed to excessive noise were used as controls. All subjects were interviewed and submitted to physical examination, pure tone and speech audiometry, immittance testing and nocturnal polysomnography. Comparative analysis demonstrated that the two groups were similar, except for the exposure to noise. Fisher's test comparison of pure tone and speech audiometry and immittance testing revealed mild to moderate noise-induced hearing loss (P < 0.001) in the > or = 85-dB group. Indicators of sleep continuity were abnormal in both groups, demonstrating poor sleep quality; however, sleep quantity was normal. Of the 40 individuals, 13 (32.5%) presented respiratory sleep disorders. Of those 13, 10 presented daytime somnolence according to the Epworth Scale. The Mann-Whitney test showed that sleep was identical in the two groups. Fisher's exact test revealed no association between altered sleep and hearing status in either group. Our results show that active men working 40-hour-a-week in the presence of excessive noise without adequate protection for more than eight years presented with noise-induced hearing loss but their quality or quantity of night sleep was unaffected. Sensori-neural deafness may represent an element of adaptation against noise during sleep.