Sleep traits and thyroid gland: results from National Health and Nutrition Examination Survey 2007-2012 and Mendelian randomization analyses

Background: Common sleep problems reduce quality of life and increase chronic disease risk. The relationship between sleep traits and thyroid function is unclear. This study explores the association between sleep traits and thyroid using NHANES data and Mendelian randomization (MR) analysis. Materials and Methods: Data from NHANES 2007-2012 were used to assess the relationship between sleep traits and thyroid function using weighted multivariable-adjusted logistic regression. A two-sample MR study was conducted using GWAS summary statistics, and methods like Inverse Variance Weighted (IVW) were used to explore the causal relationship between sleep traits and thyroid disease. Sensitivity analysis ensured robustness. Results: The study included 6919 NHANES participants. Logistic regression showed higher TSH levels in the long sleep group (P < 0.0001, β= 0.85, 95% CI: 0.54, 1.15). Lower FT3 levels were found in the normal sleep group (P = 0.0030, β= -0.06, 95% CI: -0.06, -0.00). TT4 levels were lower in those with sleep disorders (P = 0.0157, β= -0.11, 95% CI: -0.20, -0.02). Long sleep was positively associated with TGAb positivity (P = 0.0288, OR = 1.81, 95% CI: 1.06, 3.07), while sleep disorders were negatively associated with TGAb positivity (P = 0.0176, OR = 0.72, 95% CI: 0.56, 0.95). MR analysis indicated a positive association between long sleep and Graves' disease (GD) risk (P = 0.0240, OR = 99.98, 95% CI: 1.83, 5453.63), and a negative association between sleep duration and Hashimoto's thyroiditis (HT) risk (P = 0.0294, OR = 0.72, 95% CI: 0.54, 0.97). Conclusion: Sleep duration is associated with thyroid hormone levels and autoimmunity. Long sleep is linked to higher TSH levels, lower FT3 levels, and increased TGAb positivity risk, while sleep disorders are linked to lower TT4 levels and decreased TGAb positivity risk. MR studies suggest long sleep may increase GD risk, while shorter sleep may decrease HT risk.