Each pack of cigarettes sold in the United States costs the nation $7 in medical care and lost productivity, the government said Thursday.

The study by the Centers for Disease Control and Prevention put the nation's total cost of smoking at $3,391 a year for every smoker, or $157.7 billion. Health experts had previously estimated $96 billion.

Americans buy about 22 billion packs of cigarettes annually. The CDC study is the first to establish a per-pack cost to the nation.

The agency estimated the nation's smoking-related medical costs at $3.45 per pack, and said job productivity lost because of premature death from smoking amounted to $3.73 per pack, for a total of $7.18.

The average cost of a pack of cigarettes in 1999 was $2.92.

"There's a big difference in the cost to society and what society is getting back in tax," said the CDC's Dr. Terry Pechacek. "We believe society is bearing a burden for the individual behavioral choices of the smokers."

The CDC said it analyzed expenses, both personal and for the health care industry, and used national medical surveys to calculate the costs to the nation.

The agency also reported that smoking results in about 440,000 deaths a year in the United States, up from the government's previous figure of 430,000, established in the early 1990s. The new study was conducted from 1995 to 1999.

"The fact that nearly half a million Americans lose their lives each year because of smoking-related illnesses is a significant public health tragedy," said Dr. David Fleming, the CDC's acting director.

A spokesman for tobacco giant Brown & Williamson objected that the study presents the figures in a vacuum, without comparing smoking to the financial burdens other people — nonsmokers with diabetes, for example — place on society.

"What does that number mean?" spokesman Mark Smith said. "It doesn't mean anything. It's bordering on meaningless."

Representatives from the nation's two other leading tobacco companies — Philip Morris and R.J. Reynolds — did not immediately return calls for comment.

Among other findings:

— Smoking causes an average man to lose more than 13 years of life, and an average woman to lose 14.5 years.

— Smoking during pregnancy causes about 1,000 infant deaths each year.

— Lung cancer causes the most deaths among smokers, following by heart disease and lung disease.

— Men account for about 60 percent of smoking deaths — 264,000 a year, compared with 178,000 deaths among women.