Individual differences in the cortisol-awakening response during the first two years of shift work: A longitudinal study in novice police officers

Abstract

Cortisol acts as a critical biological intermediary through which chronic stressors like shift work impact upon multiple physiological, neuro-endocrine and hormonal functions. Therefore, the cortisol awakening response (CAR) is suggested as a prime index of shift work tolerance. Repeated assessments of the CAR (calculated as MnInc) in a group of 25 young novice police officers showed that in the interval between about 4 and 14 months after transitioning from regular day work to rotating shift work, mean values began to rise from baseline to significantly higher levels at about 14 months after they commenced shift work. Visual inspection of the individual trends revealed that a subgroup of 10 subjects followed a monotonically rising trend, whereas another 14 subjects, after an initial rise from about 4-14 months, reverted to a smaller, baseline level cortisol response at about 20 months after the start of shift work. If the initial increase in the cortisol response marks the development of a chronic stress response, the subsequent reversal to baseline levels in the subgroup of 14 participants might be indicative of a process of recovery, possibly the development of shift work tolerance.

Impact of shift work on the diurnal cortisol rhythm: a one-year longitudinal study in junior physicians

“…Furthermore, we recruited relatively larger sample size empowering our ability to detect fairly modest associations with statistical significance compared to most of earlier studies. To our knowledge, our study also produced first evidence of a longitudinal link between shift work and the cortisol slope, in addition to existing longitudinal findings on waking cortisol and total cortisol AUC [ 43 , 44 ]. Nevertheless, our study also suffered several limitations.…”

“…Therefore, the three longitudinal studies in the past decade deserve a close look. The Dutch study found an increase in waking salivary cortisol when police officers commenced duty of shift work 1 year later, and the effect was maintained for almost 2 years [ 44 ], while the German study, among industrial workers, suggested more cortisol secretion in saliva as larger AUC by changing work schedule from day shift to night shift for 2 months [ 43 ]. However, these two studies did not set an external reference group, that is, pre-and-post comparisons were actually conducted within subjects.…”

“…When the follow-up period is prolonged, the findings seem to become mixed. Kudielka et al followed up a sample of German workers in an electronic manufacturing plant for 2 months, and they reported that AUC of salivary cortisol was significantly increased in the group of night shift [ 43 ]; similarly, a Dutch study in police officers suggested waking salivary cortisol began to rise from baseline to significantly higher levels at one-year follow-up after they started shift duty, then declined slightly at two-year follow-up [ 44 ]. However, Copertaro et al did not confirm any significant association of shift work with serum cortisol among Italian nurses with one-year follow-up [ 45 ].…”

Impact of shift work on the cortisol awakening response and stress: a longitudinal study in female shifting monthly nurses

“…Shift work exerts influence on multiple physiological, neuroendocrine, and hormonal functions. As a result, CAR is currently considered to be a major index of shift work tolerance [27]. Research has shown that changes in CAR may be the result of increased stress and impaired sleep quality following shift changes; however, controlling for shift factor revealed no significant differences in CAR variations [28].…”

Police stressors and health: a state-of-the-art review

“…Circadian adaptation to night shift work was associated with better performance, alertness, mood, and more sleep (Boudreau et al ., 2013). Adaptation was also demonstrated in increasing and later decreasing cortisol awakening response in young novice police officers between 4 and 14 months after beginning rotating shift work (Lammers-van der Holst and Kerkhof, 2015a) Physicians should be attentive to possible sleep disorders in shiftworking police officers and health promotion programs should attempt to reduce chronic stress (Garbarino, De Carli, Nobili, Mascialino, Squarcia, Penco, Beelke, and Ferrillo, 2002; Gerber et al ., 2010). Fatigue management programs should include education, screening for sleep disorders, and interventions on health consequences (Barger et al ., 2009).…”