Journal of Health and Safety at Work

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Introduction: According to the literature, a large number of people working in industries and service providing personnel, such as firefighters, physicians, and nurses, are shift workers. The spread of shift working in industrial societies and the incidence of the problems resulting from shift working have caused the researchers to conduct studies on this issue. The present study also aimed to investigate melatonin and cortisol circadian rhythms in the security guards of Shiraz University of Medical Sciences, Shiraz, Iran.

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Material and Method: The present study was conducted among 20 security guards of Shiraz University of Medical Sciences. In order to collect the required data, blood samples were taken from the participants in different times of the day (1, 4, 7, 10, 13, 16, 19, and 22) and cortisol and melatonin levels were determined using radioimmunoassay and enzyme immunoassay techniques, respectively. Then, the data were entered into the SPSS statistical software (v. 16.0) and analyzed using One-Way ANOVA.

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Result: The results showed that as the intensity of light increased during night time, the level of plasma cortisol increased, as well. Besides, no statistically significant difference was found between the plasma cortisol levels in natural light and 4500-lux light. On the other hand, a significant difference was observed between the level of plasma cortisol in natural light and 9000-lux light as well as 4500- and 9000-lux lights. The study findings also showed that as the intensity of light increased at night, the level of plasma melatonin decreased. In addition, a statistically significant difference was found between the plasma melatonin levels in natural light and 4500-lux light. Nevertheless, no significant difference was observed between the plasma melatonin levels in natural light and 9000-lux light as well as 4500- and 9000-lux lights.

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Conclusion: The present study aimed to investigate the subsequences of shift working in the security guards of Shiraz University of Medical Sciences and showed that occupational exposure to bright light could affect some biological markers, such as melatonin and cortisol secretion.

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Introduction: This paper aims to explore the main effect of night shift rotation speed on the pattern of melatonin secretion and the sleepiness, among control room operators (CORs) in a petrochemical industry
Material and method: In this study, 60 CORs operators within two different patterns, including 7 nights and 3 nights shift works were selected from a petrochemical industry to investigate the influence of rotation speed on their melatonin secretion and the sleepiness pattern. Thus, melatonin was sampled from saliva, and the sleepiness and sleep quality were assessed using Karolinska Sleepiness Scale (KSS) index. Data analysis was carried out using spss18, Chi square, t-test, and GLM model.
Results: Melatonin values and their general changes during shift were noticeably different in two proposed patterns (P <0.05). The sleepiness index was significantly different only at 3:00 in both patterns, whereas the interaction of light and caffeine on both melatonin changes and sleepiness was not significant (P <0.05). Moreover, a significant difference was observed between the process of melatonin changes and sleepiness in the two studied patterns (P <0.05).
Conclusion: Adopting slower shift schedules rotations would be more appropriate, from the viewpoints of the importance of alertness and performance for human error prevention, among people working in serious worksites such as control rooms.