BACKGROUND: Whether to stop oral anticoagulants after a first unprovoked venous thromboembolism (VTE) is challenging, partially due to an intriguingly higher risk of VTE recurrence (rVTE) in men after therapy discontinuation. DNA methylation (DNAm) differences between men and women might underlie this sex-biased rVTE risk difference. OBJECTIVES: To investigate sex-specific associations between DNAm at cytosine-phosphate-guanine (CpG) sites and rVTE. METHODS: In 417 unprovoked VTE patients, including 101 experiencing recurrences over a 5-year follow-up (REcurrent VEnous thromboembolism Risk Stratification Evaluation [REVERSE] I), we analyzed blood DNAm using the Illumina EPIC array and performed a sex-stratified epigenome-wide association study. We further examined 181 major provoked VTE patients, including 36 recurrences over a 14-year follow-up (the MARseille THrombosis Association [MARTHA]), to investigate whether DNAm is a risk factor for rVTE after anticoagulation therapy. RESULTS: Hypomethylated CpGs at genes TBC1D22B-cg01060850 and ZHX2-cg07808424 in men and DIP2B-ch.12.1038646R and DENND3-cg03401656 in women were associated with rVTE at genome-wide level (P <
7x10-8). Though not statistically significant, DENND3-cg03401656 had the same direction of effect in MARTHA women. Sensitivity analysis confirmed the robustness of the estimates, including potential confounders, adaptations of the Cox model, non-Europeans, and proximal methylation quantitative trait loci in the association. The associated CpGs were situated at genes for membrane trafficking, corroborating the participation of Rab regulatory proteins in rVTE and transcription factors. CONCLUSION: We identified DNAm marks as potential risk factors for sex-biased recurrence in unprovoked VTE. Further replication and experimental validation could refine our understanding of the regulation of the identified DNAm sites and help optimize personalized decision-making for long-term anticoagulation after a first VTE.