Dietary Selenium Intake and Indices of Insulin Resistance and Sensitivity in US Adults with Epilepsy: Evidence from NHANES 2017–2020

Background: Epilepsy is one of the most prevalent neurological disorders and is increasingly recognized to coexist with metabolic disturbances, including insulin resistance and impaired insulin sensitivity. This study aimed to examine the association between dietary selenium intake and multiple metabolic indices among adults with epilepsy. Methods: A total of 484 adults with epilepsy were identified from the National Health and Nutrition Examination Survey (NHANES). Dietary selenium intake was assessed using 24-hour dietary recalls and categorized into quartiles. Associations between selenium intake and multiple metabolic indices, including Triglyceride-glucose (TyG), Triglyceride-glucose-body mass index (TyG-BMI), Triglyceride-glucose-waist circumference (TyG-WC), homeostatic model assessment-insulin resistance (HOMA-IR), glucose-to-insulin (GI) ratio, McAuley index, and Quantitative Insulin Sensitivity Check Index (QUICKI), were evaluated using multiple linear regression models. Results: In fully adjusted models (model 4), dietary selenium intake showed a statistically significant positive association with TyG-WC in both continuous ( β = 1.69, [95% confidence interval {CI} = 1.08, 2.31]; P < 0.001) and quartile analyses ( β Q2 vs. Q1 = 290, [95% CI = 260–320], β Q3 vs. Q1 = 194, [95% CI = 159, 230], β Q4 vs. Q1 = 56.5, [95% CI = 20.0, 93.1]; P trend = 0.014). Selenium intake was also positively associated with TyG-BMI ( β = 0.433, [95% CI = 0.190, 0.675]; P < 0.001) and HOMA-IR ( β = 0.030, [95% CI = 0.02, 00.039]; P < 0.001) in continuous analyses. In contrast, insulin sensitivity indices, including QUICKI ( β Q4 vs. Q1 = −0.010 , [95% CI = −0.016, −0.005]; P < 0.001), GI ratio ( β Q4 vs. Q1 = −12.8 , [95% CI = −17.4, −8.22]; P < 0.001), and the McAuley index ( β Q4 vs. Q1 = −1.47, [95% CI = −2.02, −0.921]; P < 0.001), showed inverse associations with higher selenium intake. The association with the TyG index was non-linear after full adjustment. Conclusions: Higher dietary selenium intake was most consistently associated with increased TyG-WC, suggesting a closer link with central adiposity-related insulin resistance in adults with epilepsy. Concurrent inverse associations with insulin sensitivity indices highlight a less favorable metabolic profile at higher selenium intake levels. These findings underscore the importance of considering metabolic heterogeneity when evaluating dietary selenium exposure in individuals with epilepsy.