A double-blind trial of 97 coronary artery disease patients undergoing bypass surgery tested quercetin (500 mg twice daily) versus placebo for roughly one week. In men, quercetin improved endothelium-dependent relaxation, reduced vascular senescence and inflammaging gene signatures in arterial tissue, and cut post-operative atrial fibrillation from 18% to 4%. Plasma proteomics showed quercetin suppressed inflammatory proteins in men but paradoxically increased them in women. Single-nucleus RNA sequencing of internal thoracic artery tissue revealed that male vascular cells carried a heavy senescence and inflammaging burden that quercetin reversed, while female cells showed minimal senescence and quercetin actually worsened fibroblast inflammation. The findings highlight a striking sex dimorphism in both vascular aging biology and quercetin's therapeutic effects.
