Journal of biological rhythmsSep 26, 2023

Changes in Melatonin and Cortisol Rhythms in Police Officers Working Rotating Shifts

Circadian Biology Weekly Brief ↗PubMed ↗DOI ↗OA ↗

Updated Mar 25, 2026

Abstract

After a series of night shifts, 30% of police officers adapted to a night-oriented schedule based on .

Before shifts, 60%-89% of officers were adapted to a day schedule based on aMT6 rhythms.
71%-78% of officers were adapted to a day schedule based on rhythms before shifts.
Officers who adapted to night shifts experienced significantly larger phase-delay shifts in aMT6s (-7.3 ± 0.9 h) and cortisol (-6.3 ± 0.8 h) compared to non-adapted officers.
A large proportion of police officers remained in a state of circadian misalignment after working night shifts.

Simplified

Misalignment of behavior and circadian rhythms due to night work can impair sleep and waking function. While both simulated and field-based studies suggest that circadian adaptation to a nocturnal schedule is slow, the rates of adaptation in real-world shift-work conditions are still largely unknown. The aim of this study was to evaluate the extent of adaptation of 24-h rhythms with (aMT6s) and in police officers working rotating shifts, with a special attention to night shifts. A total of 76 police officers (20 women; aged 32 ± 5.4 years, mean ± SD) from the province of Quebec, Canada, participated in a field study during their 28- or 35-day work cycle. Urine samples were collected for ~32 h before a series of day, evening, and night shifts to assess circadian phase. Before day, evening, and night shifts, 60%-89% of officers were adapted to a day schedule based on aMT6 rhythms, and 71%-78% were adapted based on cortisol rhythms. To further quantify the rate of circadian adaptation to night shifts, initial and final phases were determined in a subset of 37 officers with suitable rhythms for both hormones before and after 3-8 consecutive shifts (median = 7). Data were analyzed with circular and linear mixed-effects models. After night shifts, 30% and 24% of officers were adapted to a night-oriented schedule for aMT6s and cortisol, respectively. Significantly larger phase-delay shifts (aMT6s: -7.3 ± 0.9 h; cortisol: -6.3 ± 0.8 h) were observed in police officers who adapted to night shifts than in non-adapted officers (aMT6s: 0.8 ± 0.9 h; cortisol: 0.2 ± 1.1 h). Consistent with prior research, our results from both urinary aMT6s and cortisol midpoints indicate that a large proportion of police officers remained in a state of circadian misalignment following a series of night shifts in dim-light working environments.

Key numbers

30%

Adaptation Rate for

Percentage of officers whose rhythms adapted to night shifts.

24%

Adaptation Rate for

Percentage of officers whose rhythms adapted to night shifts.

6.4 h vs. 5.8 h

Cumulative Sleep Difference

Average cumulative sleep per day for adapted vs. non-adapted officers during night shifts.

Full Text

We can’t show the full text here under this license.

View Full Text ↗

Changes in Melatonin and Cortisol Rhythms in Police Officers Working Rotating Shifts

Abstract

Key numbers

Full Text

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief

Abstract

Key numbers

Full Text

Related papers

You found one interesting study. We’ll send the next 7.

what lands in your inbox each week:

Recent issues from the circadian biology brief