Smoking is bad for you. You know this! Now, a long-term study of close to a million people has broadened our understanding of the harmful side-effects of smoking, and the results suggest tobacco is even more dangerous than previously believed.

Photo Credit: Ferran Jordà | CC BY-NC-ND 2.0

"A substantial portion of the excess mortality among current smokers between 2000 and 2011 was due to associations with diseases that have not been formally established as caused by smoking," researchers report today in The New England Journal of Medicine.

Denise Grady elaborates at The New York Times:

[The] study adds at least five diseases and 60,000 deaths a year to the toll taken by tobacco in the United States. 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.

Your initial reaction to this study might be "well yes, of course, smoking is terrible, isn't that obvious?" Well yes, it is terrible. But it isn't always obvious. This kind of investigation not only contributes to our broader understanding of public health, it also helps inform the policies that support it, and identify more specifically where previous policies may have fallen short:

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 United States 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.

Many more details at the NYT. Read the full report at the NEJM.