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

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 nonworking days, cortisol levels showed similar kinetic pattern in both nurses. On working days, daytime 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.