Sleep Disturbances and Metabolic Syndrome in Shift Workers: A Systematic Review

Background: Poor sleep has been identified as a strong risk factor for metabolic syndrome. Shift workers, who often experience reduced and misaligned sleep due to nighttime work schedules, are particularly susceptible to both sleep disturbances and metabolic syndrome. However, the interplay among shift work, sleep disturbances, and metabolic syndrome remains insufficiently explored. This systematic review aimed to critically appraise, compare, and synthesize the current evidence on the pathways linking these factors. Methods: A comprehensive literature search was conducted across major electronic databases and peer-reviewed journals specializing in metabolic disorders and sleep disorders. Two independent reviewers screened titles, abstracts, and full texts for relevance. Methodological quality was assessed using the Newcastle-Ottawa Scale. Results: Out of 4,982 studies identified, 15 met the predefined inclusion criteria, encompassing diverse occupational groups with fixed and rotating shift patterns and totaling 37,147 participants. Most studies demonstrated a positive association between shift work and sleep disturbances, particularly among fixed night shift workers. Longer durations of night shift exposure were linked to increased risk of metabolic syndrome. Notably, reduced sleep quantity was more strongly associated with metabolic syndrome than impaired sleep quality. The methodological quality of the included studies was moderate to high. Conclusion: This review highlights a consistent association between shift work, sleep disturbances, and metabolic syndrome. Shift work appears to impact both sleep health and metabolic outcomes independently. These findings underscore the need for targeted interventions and longitudinal studies to further elucidate causal pathways and inform occupational health strategies.