Almost 75 percent of current smokers trying to kick the habit are now highly nicotine-dependent, which is a 15-year high, a new study finds. In fact, nicotine dependence has risen 12 percent from 1989 to 2006, and the number of highly nicotine-dependent people has gone up 32 percent, according to research expected to be presented Tuesday at the American College of Chest Physicians annual meeting, in Philadelphia.