Background: Chronotype is a determinant of tolerance to shift work; however, its physiological
and psychological correlates remain insufficiently explored in healthcare workers.
This study investigated associations between chronotype, perceived stress, sleep quality,
and health behaviours in a large cohort of shift-working nurses and physicians. Additionally,
diurnal salivary cortisol patterns were characterised in a physiological subsample.
Methods: A cross-sectional study was conducted with 451 participants (77% female;
mean age 42 ± 11 years) completing validated instruments, including the Perceived
Stress Scale (PSS), Athens Insomnia Scale (AIS), Patient Health Questionnaire Somatic
Symptom Scale (PHQ-15), and reduced Morningness–Eveningness Questionnaire (rMEQ).
In addition, a prospective pilot substudy was performed in a physiological subsample
of nurses (n = 40), in which salivary cortisol was measured at three time points during
both day and night shifts. Results: Evening chronotype exhibited a higher prevalence
of insomnia (70%) and elevated AIS scores (8.2 ± 4.2, p < 0.001). In the physiological
subsample, evening types demonstrated a significantly attenuated cortisol awakening
response (6.5 ± 5.1 nmol/L, p = 0.02) and a flatter diurnal cortisol slope during
day shifts (p = 0.01). Logistic regression indicated that increased age, somatic symptom
burden, and perceived stress were significant risk factors for insomnia, whereas morningness
was protective (OR = 0.89, p = 0.003). Conclusions: Evening chronotype among healthcare
professionals is associated with altered hypothalamic–pituitary–adrenal axis regulation
and impaired sleep quality. These findings highlight the potential utility of chronotype-based
scheduling and behavioural interventions targeting circadian misalignment to improve
occupational health outcomes in shift-working populations.
