Do you smoke even a little? If so, know this: “Smoking even a single cigarette can induce changes that lead to a heart attack,” Gianos says. Lighting up increases your risk of atherosclerosis, raises your chances of blood clots, reduces blood flow and puts you at increased risk for stroke. But it’s never too late to quit and start reversing the damage. “Heart disease risk goes down 50% in the first year [after quitting] and becomes equivalent to a nonsmoker after 10 years,” Gianos says.