Yang S, Kwak S, Kwon S, et al. - Researchers examined the correlation between lifetime exposure to endogenous sex hormone and incident atrial fibrillation (AF) and subsequent ischemic stroke. They assessed over 4.6 million natural postmenopausal women aged ≥ 40 years without prior history of AF who had national breast cancer check-up between January 1, 2009, and December 31, 2014. According to findings, shorter lifetime exposure to endogenous sex hormone, that is, shorter total reproductive years (< 30 years), was linked to a 7% increased risk of AF and subsequent ischemic stroke after adjusting for confounding variables. A progressive decline in the risk of AF was observed with every 5-yearly increment in total reproductive years. However, a 3% increase in AF risk was noted in paradoxical correlation to the prolonged (≥ 2 years) use of hormone replacement therapy after menopause.