Circadian Rhythmicity Analysis Using Optimized Cosinor Models and Entropy Measures in Real Night-Shift Workers

Introduction: Shift work, particularly night shifts, disrupts circadian rhythms, adversely impacting workers' health and performance. Core body temperature (CBT) is a robust physiological marker of circadian rhythmicity, yet in real world setting it's underused due to measurement challenges. When available, traditional methods of analysis assume a fixed period (typically 24 hours) to characterize circadian oscillations. However, shift workers may exhibit non-standard or irregular rhythms, highlighting the need for more flexible and rigorous analytical approaches. In this study, we aimed to develop and apply advanced mathematical models to detect rhythmicity, quantify irregularity, and assess circadian disruptions in real-world shift work settings.