CHICAGO (CBS) — On this fifth anniversary of Illinois’ statewide smoking ban, a new medical study comes up with yet another reason to kick the cigarette habit.

The research finds that heart bypass patients who had quit smoking even a year before their surgery, suffered complications that non-smokers didn’t.

Dr. Shahab Ahkhter, of the University of Chicago, says, “All the risk factors that are important in contributing to a patient developing coronary artery disease are also important in developing bypass graft disease.”

The study finds that even a year later, smoking triggered abnormal activity of enzymes in leg veins which reduced the effectiveness of heart bypass grafting surgery.