Summary: For most people, the “stress hormone” cortisol hits its lowest point at midnight, allowing the body to recover and rest. However, new research reveals that for nurses working double shifts, this rhythm is dangerously inverted.
The study found a two-fold increase in salivary cortisol levels at midnight in double-shift workers compared to those on single shifts. The findings suggest that prolonged work schedules don’t just cause fatigue—they trigger a fundamental physiological shift that keeps the body in a state of high-alert strain when it should be at its calmest.
Key Facts
- The Normal Rhythm: Cortisol typically peaks in the early morning to provide energy for the day and gradually declines to a “floor” around midnight.
- The Double-Shift Spike: Nurses working double shifts showed cortisol levels twice as high at midnight as their single-shift colleagues.
- Physiological Strain: This elevation indicates a disruption of the circadian rhythm, reflecting intense physiological strain rather than normal alertness.
- The Study Group: Researchers monitored 52 female nurses working rotating shifts to compare the hormonal impact of standard vs. extended hours.
- Health Implications: Chronic disruption of cortisol patterns is linked to long-term health issues, including burnout, cardiovascular strain, and impaired immune function.
Source: Wiley
Levels of cortisol, often referred to as the “stress hormone,” typically peak in the early morning hours, preparing the body for the day’s challenges by increasing alertness and energy levels, and gradually decline throughout the day, reaching their lowest point around midnight.
New research in Nursing Open found an approximately two-fold increase in salivary cortisol levels at midnight in nurses working double shifts compared with those working single shifts.
The study included 52 female nurses, working in rotating shifts. The elevated salivary cortisol levels observed in double-shift workers at midnight suggest that prolonged work schedules are associated with alterations in normal cortisol patterns.
“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.
Key Questions Answered:
A: While the cortisol provides temporary energy, it’s a “emergency” response. Normally, the body uses midnight to lower blood pressure and repair tissues. When cortisol is doubled at midnight, the body never gets that recovery window, leading to chronic “wear and tear” that eventually causes physical and mental breakdown.
A: The study observed these elevated levels in active double-shift workers, suggesting that the physiological strain is an immediate consequence of the prolonged schedule. Over time, these repeated spikes can lead to permanent “circadian misalignment,” where the body forgets how to regulate stress properly even on days off.
A: Both are tough, but the double shift is a unique stressor. Rotating shifts confuse the internal clock, but the double shift overloads it. By forcing the body to stay in a “high-cortisol” state for twice the normal duration, the physiological strain is significantly more acute.
Editorial Notes:
- This article was edited by a Neuroscience News editor.
- Journal paper reviewed in full.
- Additional context added by our staff.
About this stress and circadian rhythm research news
Author: Sara Henning-Stout
Source: Wiley
Contact: Sara Henning-Stout – Wiley
Image: The image is credited to Neuroscience News
Original Research: Open access.
“The Effect of Single and Double Shift Works on Salivary Cortisol Levels in Nurses” by Fadime Ulupınar, Sibel Meler, Engin Şebin. Nursing Open
DOI:10.1002/nop2.70495
Abstract
The Effect of Single and Double Shift Works on Salivary Cortisol Levels in Nurses
Aim
This study aimed to elucidate the effects of single versus double-shift work schedules on salivary cortisol concentrations among nurses.
Design
This research was designed as a comparative descriptive study utilizing repeated measures to assess changes over time and shift types.
Methods
A total of fifty-two female nurses, working in rotating shifts, participated in the study. Saliva cortisol samples were collected from all participants before, after, and at midnight for both a single and a double shift. To assess interactions between time (07:30–08:30, 15:30–16:30, 23:00–24:00) and shift type (single and double), a repeated-measures two-way analysis of variance (ANOVA) was used.
Results
Analyses encompassing both time and shift type demonstrated significant main effects for both variables. Salivary cortisol concentrations were maximal between 07:30 and 08:30, while the trough levels were recorded at midnight. Inspection of the main effect associated with shift type revealed that double-shift workers exhibited higher mean cortisol concentrations.
Specifically, cortisol levels were nearly two-fold higher at midnight in double-shift workers compared to single-shift workers. Additionally, a significant interaction effect between time and shift type was found.
Conclusion
The pronounced effects of double shifts, as evidenced by significant changes in cortisol levels, warrant urgent consideration by healthcare policymakers and administrators, balancing operational efficiency with nurses’ well-being and patient safety.
Patient or Public Contribution
No patient or public contribution.
