Twenty Four- Hour Circadian Melatonin Profile Among Women Shift Work Nurses

Background and Objective: According to previous studies shift work could desynchronize the natural circadian rhythm of the body. Although some of the internal physiologic processes become active for adaptation of the body with this desynchronization. One of these physiologic processes is endocrine system and melatonin release. This hormone is one of the most important variants which represent the circadian rhythm in human. Since the pattern of secretion of this hormone in first ours of morning and during the day in Iranian workers in particular in shift workers is unknown, therefore we aimed to determine the ۲۴ hours profile of melatonin in shift work and permanent day shift nurses. Materials and Methods: This experimental study was carried out on forty four female nurses of the Shiraz university hospital, during ۲۰۰۶-۲۰۰۸. Thirty four people in study group had a cyclic shift work and ۱۰ persons in control group had permanent day shift work. The serum samples with ۳ hours intervals during ۲۴ hours were taken from each person. The plasma concentration of melatonin was measured by ELISA. Our study was carried out under realistic conditions. The data were analyzed using one –way ANOVA. Results: The age range was between ۲۲ to ۵۰ years with a mean work history of ۵.۵ years. The highest and the lowest melatonin levels was found in shift work nurses at ۰۴:۰۰ pm (۱۴.۹۱ pg/mL), and ۰۴:۰۰ am (۱۳۱.۴۹ pg/mL). These values for permanent day work nurses in the same times was ۱.۰۲ pg/mL and ۱۷۷.۴۰ pg/mL respectively. There was a significant difference between circadian melatonin profile at different time points (P= ۰.۰۰۰). Conclusion: The results of this study revealed that night work induces a consistent change in melatonin circadian profile with a progressive reduction at early morning (۰۴:۰۰ am) and awaking time (۰۷:۰۰ am). These changes will also disturb sleep cycle and level of consciousness during the night and activities during the day.

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Key words: Melatonin , Female nurses , Shift work