Association of a Dietary Index for Gut Microbiota With Epilepsy Among US Adults Aged 40 and Over: A Cross-Sectional Study.

BACKGROUND: Epilepsy remains difficult to control in some patients, motivating interest in modifiable factors linked to seizure biology. Because diet can shape gut microbial ecology and gut-brain signaling, we examined whether the dietary index for gut microbiota (DI-GM) was associated with prevalent epilepsy in US adults aged ≥ 40 years. METHODS: This cross-sectional study included 5025 participants from NHANES 2013-2016. DI-GM was constructed from 14 predefined dietary components reflecting microbiota-supportive or microbiota-adverse intake. NHANES sampling weights were applied. Multivariable logistic regression evaluated associations between DI-GM and prevalent epilepsy. Restricted cubic splines, subgroup analyses, and weighted quantile sum (WQS) regression were used to examine dose-response shape, effect heterogeneity, and component contributions. RESULTS: In the fully adjusted model, DI-GM showed an inverse association with prevalent epilepsy (OR per 1-point increase, 0.80; 95% CI, 0.69-0.93; p = 0.008). Compared with Q1, Q4 had lower epilepsy odds (OR, 0.29; 95% CI, 0.10-0.87; p = 0.033). The spline analysis did not support nonlinearity (p = 0.663). The inverse association was mainly seen among adults without hypertension or diabetes, with significant interaction by hypertension (p < 0.001) and diabetes status (p = 0.003). WQS results highlighted cranberries, chickpeas, avocados, soybeans, and lower processed meat intake as major contributors. CONCLUSIONS: Higher DI-GM adherence was associated with lower odds of prevalent epilepsy, particularly in metabolically healthier subgroups. Prospective and intervention studies are needed to test temporality and clinical relevance.