Circadian rhythm disruption and hormonal alterations in shift-working nurses: An integrative review

Abstract

Shift work and working during the night have emerged as major contributors to the disruption of our natural circadian rhythms. This integrative review synthesises evidence on shift-work induced circadian rhythm disruption and associated hormonal dysregulation. Eight databases were searched for relevant literature published between 2016 and 2026 (PubMed, Web of Science, Scopus, CINAHL, Embase, Cochrane Library, and ProQuest, and Google Scholar). Article quality was appraised using the 2018 Mixed Methods Appraisal Tool (MMAT). Twenty-two studies met the eligibility criteria. Circadian disruption was evaluated using objective parameters (urinary 6-sulfatoxymelatonin, cortisol profiling, actigraphy, core body temperature, clock gene expression) and subjective questionnaires (PSQI, MCTQ, MEQ). Shift working nurses consistently demonstrated suppressed melatonin secretion, delayed circadian phase, flattened cortisol awakening responses, and elevated nocturnal cortisol. Prolonged shift work was linked to reproductive alterations (elevated estradiol, earlier menopause), metabolic dysregulation (increased nighttime insulin and leptin), systemic inflammation (elevated TNF-alpha, IL-1beta, IL-6), altered clock gene expression (PER2, PER3, BMAL1, ESR2), and endothelial and neurological impairments. Shift work drives widespread circadian and neuroendocrine dysregulation across metabolic, reproductive, immune, and cardiovascular systems in nurses. Evidence-based occupational health strategies and circadian-aligned scheduling are essential to reduce these long-term physiological health risks.