Network Mendelian randomization study: exploring the causal pathway from insomnia to type 2 diabetes

Area of Science:

• Genetics and Epidemiology
• Metabolic Disease Research

Background:

• Insomnia is increasingly recognized as a significant risk factor for type 2 diabetes mellitus (T2DM).
• The precise biological mechanisms connecting insomnia and T2DM remain incompletely understood.
• Identifying mediating factors is crucial for understanding and potentially intervening in this relationship.

Purpose of the Study:

• To investigate the causal association between insomnia and T2DM using a network Mendelian randomization (MR) framework.
• To identify potential mediating factors, specifically overweight indicators (BMI, waist-to-hip ratio, body fat percentage) and glycometabolic markers (HbA1c, fasting blood glucose, fasting blood insulin), in the insomnia-T2DM pathway.

Main Methods:

• A network Mendelian randomization (MR) framework was employed to assess causal relationships.
• Effect estimates for insomnia-T2DM, insomnia-mediator, and mediator-T2DM associations were determined.
• The Inverse Variance Weighted (IVW) method was utilized, alongside assessments for heterogeneity and horizontal pleiotropy.

Main Results:

• Genetically predicted insomnia was found to significantly increase the risk of T2DM (OR 1.142, p=0.000).
• Strong evidence indicated a causal link between insomnia and increased Body Mass Index (BMI) and body fat percentage.
• While insomnia was not causally linked to glycometabolic markers, higher BMI, waist-to-hip ratio, and body fat percentage were strongly associated with T2DM risk.

Conclusions:

• Genetically predicted insomnia is causally associated with an increased risk of developing T2DM.
• Overweight conditions, particularly elevated BMI and body fat percentage, act as significant mediators in the causal pathway from insomnia to T2DM.
• These findings underscore the importance of managing weight-related factors in individuals experiencing insomnia to mitigate T2DM risk.