CHRONOTYPE-DEPENDENT HPA-AXIS ALTERATIONS IN ROTATING SHIFT WORKERS: NEUROENDOCRINE AND BEHAVIOURAL CORRELATES

Objective: Rotating shift work disrupts circadian homeostasis by desynchronizing the central pacemaker (suprachiasmatic nucleus) from peripheral oscillators. Chronotype influences susceptibility to circadian misalignment, with implications for hypothalamic–pituitary–adrenal (HPA) axis regulation, sleep, and psychological wellbeing. We examined neuroendocrine and behavioural stress markers in shift-working healthcare professionals, focusing on evening chronotype vulnerability.
Methods: Within a cross-sectional observational framework (n=318), a neuroendocrine subsample (n=40) of nurses was evaluated. Salivary cortisol, blood pressure, and heart rate were measured at awakening+30 min, 18:00, and 22:00 during day and night shifts. Validated instruments assessed perceived stress (Perceived Stress Scale, PSS), insomnia severity (Athens Insomnia Scale, AIS), somatic symptoms (Patient Health Questionnaire, PHQ-15), sleep hygiene (Sleep Hygiene Index, SHI), and chronotype (Reduced Morningness–Eveningness Questionnaire, rMEQ).
Results: Night shifts induced elevated 18:00 cortisol and increased autonomic arousal at 22:00 compared to day shifts (p<0.001). Evening chronotype displayed a blunted cortisol awakening response (6.5±5.1 nmol/L, p=0.02), flatter diurnal cortisol slope during day shifts (p=0.01), and higher AIS scores (8.4±4.1, p=0.004) with 75% reporting insomnia. General linear modeling identified insomnia severity as predicted by PSS, PHQ-15, night-shift frequency, SHI, and evening chronotype (all p≤0.01).
Conclusions: Evening chronotype may be particularly vulnerable to circadian misalignment during rotating shift work, demonstrating altered HPA-axis activity and poorer sleep. Chronotype-informed scheduling and flexible shift systems could mitigate physiological and psychological strain in healthcare staff.