Half a million die from smoking yearly in U.S.

Smoking causes half a million deaths each year in the U.S., killing slightly more men than women, new statistics show.

A new study in The Journal of the American Medical Association confirms that trend: about 7 percent of adults in the U.S. were heavy smokers in 2007, compared to 23 percent in 1965. The researchers on that study, led by Dr. John Pierce of the University of California, San Diego, defined "heavy smoking" as 20 or more cigarettes a day.