Effects of Prolonged Night Shifts on Salivary <i>α</i>-Amylase, Secretory Immunoglobulin, Cortisol, and Chromogranin A Levels in Nurses

Abstract

Prolonged night shift is associated with high burnout rate, but the physiological effects of a 16 h shift remain undetermined. Here we evaluated fatigue and stress via salivary assays to determine the correlation between stress and fatigue and prolonged night shifts. Twenty-five nurses (9 men, 16 women; 16 h night shift (n = 13), 8 h day shift (n = 12)) from Juntendo University Koshigaya Hospital were evaluated for four consecutive workdays separated by off days. Salivary samples were collected upon waking and before sleep on non-working days, before and after the day and night shifts, and before and after the break during the nocturnal schedule, and analyzed for levels of cortisol, chromogranin A, α -amylase activity and secretory immunoglobulin A (sIgA). On non-working days, cortisol levels showed similar kinetic pattern in both nurses. On working days, day-time nurses’ cortisol levels showed normal circadian pattern throughout the shift. Night nurses’ cortisol levels at the beginning of the shift were comparable to that of the normal morning elevation. α -Amylase activity in the night shift nurses was higher than day shift nurses through each period. No significant differences in chromogranin A and sIgA levels were detected between day and night shift workers. A 16 h night shift may cause marked circadian misalignment in cortisol levels.