Sleep Traits and Hypothyroidism: A Two-Sample Bidirectional Mendelian Randomization Study

Background: While the link between hypothyroidism and disturbed sleep patterns has been recognized, the available data are inconsistent, making it difficult to establish causality. This study aimed to investigate the causal relationship between certain sleep traits and hypothyroidism. Methods: Using publicly available genomewide association study (GWAS) data, we applied linkage disequilibrium score regression (LDSC) to identify genetic associations between hypothyroidism and various sleep traits. Two-sample Mendelian randomization (MR) analysis was then conducted to assess the causal relationship between aberrant sleep features and the risk of hypothyroidism. The IVW, MR-Egger regression, weighted median, and weighted mode methods were used. To detect level polymorphism and outliers, MR-Egger regression and MR-PRESSO methods were employed. Results: A genetic association between hypothyroidism and nap during the day and getting up in morning (rg=-0.0982, p=0.0007; rg=-0.101, p=0.0001). In addition, a causal relationship between hypothyroidism and sleep duration (IVW, OR 1.5208, 95%CI: 0.1082-0.7304, P=0.0082) and getting up in morning (IVW, OR 1.8375, 95%CI: 0.3717-0.8452, P=4.73×10-7). Furthermore, the reverse MR analysis did not reveal any causal link between hypothyroidism and aberrant sleep traits. Conclusion: MR analysis demonstrated a causal link between hypothyroidism and certain aberrant sleep traits. Sleep duration should be considered as a potential factor in disease models for improving sleep quality and reducing the risk of hypothyroidism.