The Significance of Sleep in Glucose Metabolism Regulation – The Role of Circadian Rhythm Disruptions in Type 2 Diabetes Development: A Narrative Review

Background: Sleep and circadian rhythm disturbances constitute modifiable risk factors for type 2 diabetes mellitus (T2DM). Meta-analytic evidence demonstrates that short sleep duration (<6h/night) increases T2DM risk by 28–33% (OR 1.28–1.33), while shift work elevates incidence by 9–40% (RR 1.09–1.40). Aims: The aim of this narrative review is to synthesise current epidemiological, interventional, and mechanistic evidence on how sleep disturbances and circadian rhythm disruptions influence type 2 diabetes pathophysiology in adults. Methods: A structured narrative review was conducted using literature from PubMed, Scopus, Web of Science, and Google Scholar (2015–2025). Searches employed terms: "sleep duration glucose metabolism", "circadian rhythm type 2 diabetes", "clock genes insulin resistance", "shift work diabetes risk", "melatonin glucose homeostasis". Meta-analyses, systematic reviews, cohort studies, and randomized controlled trials were included. Results: Epidemiological evidence reveals a U-shaped sleep–T2DM relationship with optimal risk at 7–8 hours/night. Short sleep (<6h) and long sleep (>9h) both increase T2DM risk (OR 1.28–1.48). Night shift work elevates risk dose-dependently (RR 1.40, 95% CI 1.15–1.71) across 1.16 million participants. Molecular mechanisms involve desynchronized clock genes (CLOCK, BMAL1, PER2, CRY1), mitochondrial dysfunction reducing oxidative capacity 20–30%, and altered melatonin signaling. Sleep extension interventions improve insulin sensitivity 17–45% within 1 week. Evening chronotherapy with glucose-lowering drugs demonstrates superior efficacy compared to morning dosing. CBT-I (cognitive behavioral therapy for insomnia) reduces T2DM incidence by 42% in prediabetic populations. Conclusion: Sleep and circadian optimization represent cost-effective, modifiable strategies for T2DM prevention. Personalized chronotherapy guided by genetic profiling and objective sleep/activity monitoring warrants implementation in clinical practice and public health policies.