Effect of occupational noise on the nocturnal sleep architecture of healthy subjects.

ABSTRACT

BACKGROUND & OBJECTIVES: Noise is considered to be a non-specific stressor which generally causes physiological and psychological effects in an individual. Many occupations involve workers being subjected to loud noise levels without adequate protective measures. The study was done to document the changes, if any, in the nocturnal sleep architecture of healthy persons exposed to loud occupational noise during daytime. METHODS: The study was a retrospective cohort design wherein three groups of eight subjects each, exposed to continuous occupational background noise levels of >75dB for 1-2 years, 5-10 years and >15 years were selected. Corresponding age and gender matched healthy controls (eight for each group) who worked in a quiet atmosphere was also recruited. All night sleep polysomnography was done on all subjects. In the morning, subjects rated their quality of sleep on a Visual Analogue Scale. RESULTS: There is a strong association between occupational exposure to loud noise and poor sleep efficiency (Relative Risk 2.49; Confidence Interval 1.12 to 5.57; P=0.01, Fisher's exact test). The group exposed to noise for 1-2 years had a decrease in Total Rapid Eye Movement Time, Non Rapid Eye Movement Time, Slow Wave Sleep Time, Sleep Onset Latency and Total Sleep Time. The other two groups showed lesser number of changes in sleep architecture. Subjectively there was a decrease for sleep continuity in Group I and an increase for sleep onset in Group II. There is no correlation between loudness of noise in the workplace and sleep efficiency. INTERPRETATION & CONCLUSION: It can be concluded that workers exposed to loud background occupational noise are at an increased risk of having poor quality sleep but adaptation to this effect probably takes place after a few years.