Effect of Circadian Rhythm Disruption on Fatigue Among Pilots: Narrative Review

Background: The aviation environment exposes pilots to multiple circadian challenges including night operations, trans meridian travel, irregular scheduling, and fluctuating workload intensity. These factors contribute to acute and chronic fatigue, a recognized threat to operational safety and pilot health. Objective: This review synthesizes current scientific evidence on circadian rhythm biology, fatigue pathophysiology, demographic and operational risk determinants, and fatigue assessment tools, with a focus on applications to global aviation and emerging sectors such as Iraq. Methods: A narrative review approach was used to examine peer-reviewed studies published in aviation medicine, chronobiology, sleep research, and human factors. Databases searched included PubMed, Academic.edu, Aviat Space Environ Med, J Occup. Environ Med, SKY brary Aviation Safety, Elsevier Scopus, Web of Science, Web MD and Google Scholar. Study design included cross-sectional, cohort, review articles, thesis, survey, educational\ operational guidance, mixed method analysis and theoretical review in the last 20 years. Key finding: Findings demonstrate that circadian misalignment significantly impairs alertness, psychomotor function, decision-making, and sleep quality. Risk factors include age, chronotype, BMI, underlying medical conditions, night duties, long-haul operations, and environmental stressors. Validated tools such as the Epworth Sleepiness Scale (ESS) and Fatigue Severity Scale (FSS) remain central to fatigue evaluation. Conclusion: For rapidly developing aviation sectors, including Iraq, implementing a layered, evidence-based fatigue management strategy is essential to improve safety, enhance pilot performance, and protect long-term pilot health, as fatigue is a hazard that can be anticipated, prevented, and managed.