Effects of Rotating Night Shift and Exposure of Light at Night on Circadian Pattern of Salivary Cortisol and Urinary Melatonin Levels

Objectives: The objective of the present study was to investigate the effects of rotating night shift and light exposure at night on circadian pattern of salivary cortisol and urinary melatonin levels. Methods: 62 healthy nursing professionals of both genders performing day and night shifts (continuous 9 days night shift with alternate day shifts) were recruited. Each month scheduled to continuous 9 days night shift (12 hours in regular 9 nights, from 20:00 to 08:00); after 9 days night shift they perform remaining duties in day shift and 4 days off. Saliva and Urine samples were collected at around 8 hours interval while they were performing night duties and repeated when they were assigned day duties. Saliva and Urine samples were analyzed by the ELISA method. Results: Significant difference was found in night cortisol among night (4.34 ± 3.37) vs day shift (2.70 ± 2.32), (p<0.001). Alteration in morning cortisol was also found between night (3.73 ± 2.47) vs day shift (5.00 ± 2.73). Night melatonin level was decreased as compared to morning melatonin. Significant deference were observed when compared night melatonin between night (16.71 ± 11.98) vs day shift (22.71 ± 13.25) (p<0.001), morning melatonin between night (20.07 ± 14.13) vs day shifts (28.26 ± 14.14) (p<0.001). The circadian pattern of cortisol and melatonin was altered by rotating night shift particularly at night and in the morning time. Conclusion: The present study concluded that the desynchronization was appeared during night shift and entrainment of circadian rhythm in the day shift.