The healthy habits people adopt and stick with in their 20s and 30s have a massive and direct impact on their risk of a heart attack or stroke decades later, a landmark study says. Young adults who fail to keep heart-healthy practices can see their risk of future heart disease skyrocket by as much as 10 times as they age, compared to those who maintain their healthy habits, researchers reported Monday in JAMA Network Open . "Change matters: Improvements in heart health can decrease future risk,