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Cigarette smoking is even more deadly than you think, study says

The U.S. surgeon general says about 480,000 Americans die each year as a result of smoking. But a new analysis suggests the true figure may be closer to 575,000.

The 21 causes of death that have been officially blamed on smoking accounted for 83% of the actual deaths among smokers who were tracked in a study published in Thursday’s edition of the New England Journal of Medicine.

Additional diseases -- including breast cancer, prostate cancer, hypertensive heart disease and renal failure -- were responsible for most of the rest of the observed deaths. A very small number of deaths were due to things such as accidents and suicide, which have a more tenuous link to smoking.

Researchers from the American Cancer Society, the National Cancer Institute and elsewhere combined data from five large, ongoing health studies: the Nurses’ Health Study I, the Women’s Health Initiative, the Health Professionals Follow-up Study, the Cancer Prevention Study II and the National Institutes of Health-AARP Diet and Health Study. The researchers included 954,029 men and women who were being tracked as of Jan. 1, 2000, and who had told interviewers about their smoking status.

Between 2000 and 2011, 16,475 (19%) of the 88,616 smokers died, as did 108,253 (23%) of the 469,141 former smokers and 56,649 (14.3%) of the 396,272 people who had never smoked, according to the study.

Smokers were more likely than nonsmokers to have died from one of the established smoking-related diseases, the researchers found. These included most kinds of heart disease; stroke; chronic obstructive pulmonary disease; pneumonia, influenza and tuberculosis; atherosclerosis; aortic aneurysms and other arterial diseases; diabetes; acute myeloid leukemia; and cancers of the lung, pancreas, colon and rectum, kidney, liver, bladder, larynx, lip and oral cavity, stomach and esophagus.

These diseases were responsible for the overwhelming majority of deaths among men and women who were still smoking at the end of their lives.

But not all of them. Another 17% of deaths among female smokers and 15% of the deaths of male smokers were traced to other causes.

In nearly every case, the diseases in this second group were more likely to kill current smokers than nonsmokers, according to the study.

For instance, female smokers were 30% more likely to die of breast cancer than their non-smoking counterparts, and men who smoked were 40% more likely to die of prostate cancer than their non-smoking peers. Rare cancers were 60% more likely to kill men if they were smokers, the researchers found.

The risk of death due to infections was more than twice as high for smokers than for nonsmokers. Ditto for hypertension, hypertensive renal disease and a range of digestive diseases.

Smokers were 2.6 to 3.6 times more likely than nonsmokers to die of liver cirrhosis and 1.9 to 2.1 times more likely to die of kidney failure. Hypertensive heart disease, some kinds of respiratory diseases and ischemic disorders of the intestines were also more likely to kill smokers than nonsmokers, the study authors calculated.

The more cigarettes a person smoked per day, the greater his or her risk of dying from infections, breast cancer or kidney failure. Among those who quit, the longer it had been since the last cigarette, the lower the risk of dying from infections or breast cancer, according to the report.

The researchers laid out the biological mechanisms that could plausibly explain why some of these diseases would be more likely to kill smokers. In the case of infections, for example, cigarette smoke is known to hinder immune function. Smoking is also known to reduce blood flow to the intestines, potentially explaining the link to intestinal and digestive diseases.

Compared to the U.S. population as a whole, the people included in this study were more likely to be white and to be highly educated. That limits researchers’ ability to generalize the findings to the entire country.

Still, the study authors didn’t hesitate to say that the surgeon general should go back and check the math.

“Our results suggest that the number of persons in the United States who die each year as a result of smoking cigarettes may be substantially greater than currently estimated,” they wrote.