Feb. 12: However bad you thought smoking was, it's even worse.

A new study adds at least five diseases and 60,000 deaths a year to the toll taken by tobacco in the US. Before the study, smoking was already blamed for nearly half a million deaths a year in this country from 21 diseases, including 12 types of cancer.

The new findings are based on health data from nearly a million people who were followed for 10 years. In addition to the well-known hazards of lung cancer, artery disease, heart attacks, chronic lung disease and stroke, the researchers found that smoking was linked to significantly increased risks of infection, kidney disease, intestinal disease caused by inadequate blood flow, and heart and lung ailments not previously attributed to tobacco.

Even though people are already barraged with messages about the dangers of smoking, researchers say it is important to let the public know that there is yet more bad news.

"The smoking epidemic is still ongoing, and there is a need to evaluate how smoking is hurting us as a society, to support clinicians and policy making in public health," said Brian D. Carter, an epidemiologist at the American Cancer Society and the first author of an article about the study, which appears in The New England Journal of Medicine. "It's not a done story."

In an editorial accompanying the article, Dr.Graham A. Colditz, from Washington University School of Medicine in St. Louis, said the new findings showed that officials in the US had substantially underestimated the effect smoking has on public health. He said smokers, particularly those who depend on Medicaid, had not been receiving enough help to quit.

About 42 million Americans smoke - 15 per cent of women and 21 per cent of men - according to the Centers for Disease Control and Prevention. Research has shown that their death rates are two to three times higher than those of people who have never smoked, and that on average, they die more than a decade before non-smokers. Smokers are more than 20 times as likely as non-smokers to die of lung cancer. Poor people and those with less formal education are the most likely to smoke.

Carter said he had been inspired to dig deeper into the causes of death in smokers after taking an initial look at data from five large health surveys being conducted by other researchers. The participants were 421,378 men and 532,651 women 55 and older, including nearly 89,000 current smokers.

As expected, death rates were higher among the smokers. But diseases known to be caused by tobacco accounted for only 83 per cent of the excess deaths in people who smoked. "I thought, 'Wow, that's really low,'" Carter said. "We have this huge cohort. Let's get into the weeds, cast a wide net and see what is killing smokers that we don't already know."

The research was paid for by the American Cancer Society, and Carter worked with scientists from four universities and the National Cancer Institute.