At the TIME100 Health Impact Dinner in New York City on Thursday, TIME executive editor Nikhil Kumar kicked off a panel discussion with one big question: Why is heart disease still the leading cause of death for men and women? “Perhaps before we answer the question of why it’s the leading cause of death today,” replied Dr. Sadiya Khan, a professor of cardiovascular epidemiology and an associate professor of medicine at Northwestern University Feinberg School of Medicine, “we have to know where