The causal role of metabolic syndrome components in insomnia: A bidirectional two-sample Mendelian randomization.

Background: The neuroendocrine system's role in maintaining bodily homeostasis implicates it in insomnia, suggesting both causal relationships and therapeutic targets. Yet, studies examining the link between metabolic syndrome (MetS) components such as hypertension, elevated blood glucose levels and abnormal cholesterol and insomnia have been inconsistent. Some research suggests a correlation, proposing that metabolic dysfunctions might contribute to sleep disturbances. However, other studies found little to no significant connection, indicating the complexity of this relationship and the potential influence of genetic, lifestyle and environmental factors. These contradictory findings underscore the challenges in fully understanding the intricate interplay between metabolic health and sleep quality.

Objectives: To explore the relationship between MetS and insomnia.

Material and methods: This study used bidirectional two-sample Mendelian randomization (MR) analysis to determine the causal relationship between the characteristics of MetS components and insomnia. Based on Genome-Wide Association Studies (GWAS) public databases, we explored the causal relationship between waist circumference (WC), hypertension, triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), fasting blood glucose (FBG), and the risk of insomnia. Sensitivity analysis was conducted to evaluate the stability, heterogeneity and potential presence of horizontal pleiotropy in the results.

Results: Waist circumference and hypertension were associated with an increased risk of insomnia (WC, odds ratio (OR) = 1.05, 95% confidence interval (95% CI): 1.03-1.06, p = 9.15e-07; hypertension, OR = 1.06, 95% CI: 1.02-1.10, p = 0.005). In the reverse MR analysis, there was no significant causal relationship between insomnia and WC, TG, HDL-C, and FBG.

Conclusions: Our study has demonstrated the close connection between MetS components and insomnia by genetic means, thereby guiding the future research direction of insomnia prevention and treatment.