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چکیده
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Background: Night shift works are usually accompanied by reduced cognitive performance, sleepiness, and higher possibility for human error, and related incidents. It is, therefore, crucial to improve individuals’ performance and alertness in sensitive places like industries’ control rooms to improve efficiency and reduce the number of possible incidents. Previous research has indicated that blue light is a critical cue for entraining circadian rhythm. Objectives: As a result, the present study aimed at investigatingwhether blue-enriched white light illumination was a practical strategy to decrease melatonin and sleepiness and improve cognitive performance during the night shifts. Methods: The present study, with its before-after interventional design, was conducted on 30 control room staff members of petrochemical industry. After baseline assessments under the existing lighting conditions, every participant was exposed to 2 new lighting conditions (namely, 17,000 K and 6,500 K blue-enriched white light), each lasting for a week. Subsequently, assessments were conducted again. More specifically, melatonin assessment was conducted using salivary and Eliza technique. On the other hand, karolinska sleepiness scale (KSS) was used to assess the degree of sleepiness, while n-back cognitive test and continuous performance test were applied to measure the cognitive performance. Results: The results revealed that compared to normal lighting conditions, participants’ sleepiness and melatonin rhythm significantly declined when they were exposed to blue-enriched white light. Furthermore, the experimental condition had a significant effect on the reduction of working memory errors. It also decreased omission errors and the reaction time during the sustained attention task. Conclusions: Using blue-enriched white light may be a proper ergonomic strategy for improving performance and alertness in sensitive environments like control rooms, especially during the night time.
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