Nursing Open
Double shifts double late-night cortisol levels of nurses
Clinical takeaway: Extended shift schedules may increase physiologic stress and disrupt circadian rhythm, with potential implications for fatigue, performance, and long-term health.
Cortisol follows a predictable circadian pattern, peaking in the morning and reaching its lowest levels at night. This study examined whether double shifts alter that pattern in nurses working rotating schedules.
In this repeated-measures study of 52 female nurses, salivary cortisol was measured before, after, and at midnight during both single and double shifts.
Double shifts were associated with higher cortisol levels overall, with the most pronounced difference at midnight, where levels were nearly two-fold higher compared with single shifts. This suggests disruption of normal circadian rhythm and increased physiologic strain during prolonged work periods. Cortisol levels at the end of the shift did not differ substantially between single and double shifts.
These findings support concerns that extended and overnight work schedules may contribute to chronic stress, sleep disruption, and downstream health effects. The small sample size and single-setting design may limit generalizability.
“Our findings indicate that extended shift schedules may be associated with alterations in the circadian pattern of cortisol, reflecting increased physiological strain in nurses working prolonged hours,” said corresponding author Fadime Ulupınar, RN, MSc, of Erzurum Technical University in Turkey.
Source: Ulupınar F, et al. Nursing Open. April 8, 2026. The Effect of Single and Double Shift Works on Salivary Cortisol Levels in Nurses