Sleep habits, brain functional networks, and type 2 diabetes risk: cohort studies from North American and Asian populations and mediating Mendelian randomization analyses.

Background: Brain resting-state functional networks and sleep habits are associated with Type 2 diabetes mellitus (T2DM). However, the causal mediating effect between them remains largely unexplored.

Methods: We analyzed data from 20,994 U.S. adults in the National Health and Nutrition Examination Survey (NHANES) and 8,652 Chinese adults from the China Health and Aging Longitudinal Study (CHARLS), focusing on sleep habits and the incidence of T2DM. Two-sample Mendelian randomization (MR) was employed to assess the causal relationships between sleep habits, resting-state functional magnetic resonance imaging (rs-fMRI), and T2DM. Furthermore, a mediation analysis was conducted to examine the role of rs-fMRI in moderating the association between sleep patterns and T2DM.

Results: In the Chinese population, daytime naps lasting 0-0.25 h (β = 0.365) and more than 0.5 h (β = 0.039), along with nighttime sleep of less than 5 h (β = 0.049) and more than 9 h of sleep overall (β = 0.124) were linked to a higher risk of T2DM. Similarly, in the U.S. population, sleeping less than 5 h (β = 0.056), 5-6 h (β = 0.034), and more than 8 h (β = 0.052) also significantly increased the risk of T2DM. Moreover, sleeping in later than 1:00 a.m. or before 10:00 p.m. raises the chance of acquiring T2DM. A correlation between the incidence of T2DM and increased connectivity in the default mode network (DMN), visual network (VN), central executive network, (CEN), and motor networks (MN) was found by MR analysis. Additionally, mediation analysis revealed that sleep disorders, naps during the day, and daytime sleep affect T2DM morbidity via changing connectivity in the central executive, motor, and default mode networks.

Conclusions: According to our research, changed brain functional network connectivity and sleep habits, significantly influence the risk of T2DM. This demonstrates the critical function that brain networks play in modulating the link between sleep patterns and the prevalence of T2DM.