The effect of blue-enriched white light on cognitive performances and sleepiness of night-shift workers: A field study

• Published in: Physiology & behavior Vol. 177; pp. 208 - 214
• Main Authors: Motamedzadeh, Majid, Golmohammadi, Rostam, Kazemi, Reza, Heidarimoghadam, Rashid
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.08.2017
• Subjects: Adult; Attention - physiology; Attention - radiation effects; blue light; Blue-enriched white light; circadian rhythm; Circadian Rhythm - physiology; Circadian Rhythm - radiation effects; cognition; Cognition - physiology; Cognition - radiation effects; Cognitive performance; Enzyme-Linked Immunosorbent Assay; Humans; Light; Lighting; Male; Melatonin; Melatonin - analysis; memory; Memory, Short-Term - physiology; Memory, Short-Term - radiation effects; Neuropsychological Tests; Night work; oil and gas industry; Psychiatry; Saliva - chemistry; Shift Work Schedule - psychology; Sleep - physiology; Sleep - radiation effects; Sleepiness; Wakefulness - physiology; Wakefulness - radiation effects; white light; Work Schedule Tolerance - physiology; Work Schedule Tolerance - psychology; Cognitive performance; Melatonin; Sleepiness; Night work; Blue-enriched white light
• ISSN: 0031-9384; 1873-507X; 1873-507X
• DOI: 10.1016/j.physbeh.2017.05.008

Night-shift works are basically 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 room with the ultimate goal of increasing efficiency and reducing the number of possible incidents. Previous research has indicated that blue light is a critical cue for entraining circadian rhythm. As a result, the present study was an attempt to investigate whether blue-enriched white light illumination was a practical strategy to decrease sleepiness and improve cognitive performance during night shifts. The study, which adopted a before-after interventional design, was conducted among 30 control room staff members of petrochemical industry. After baseline assessments under existing lighting conditions, every participant was exposed to two new lighting conditions (namely, 17,000K and 6500K blue-enriched white light), each lasting for a week. Assessments were conducted again at the end of these treatments. In order to measure the subjective sleepiness, Karolinska Sleepiness Scale (KSS) was utilized. Subjects also performed the Conners' Continuous Performance Test II (CPT-II) and 1-back test in order to gauge their cognitive performance, and melatonin assessment was carried out using salivary and Eliza technique. The data was analyzed using two-way repeated measure ANOVA. The results indicated 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. Thus, using blue-enriched white light may be a proper ergonomic strategy for improving performance and alertness, especially during night, in sensitive environments like control rooms. •Blue light is known as a critical cue for entraining circadian rhythm and enhanced cognitive performance.•This interventional study investigated the influence of blue-enriched white light on melatonin, sleepiness, and cognitive performance.•Blue-enriched white light illumination can be used as a suitable strategy to reduce sleepiness and enhance cognitive performance in industrial environments at night.