Smoking and Mortality

Posted by • February 13th, 2015

Using data from five U.S. cohort studies, the authors of a new report estimate that 17% of excess mortality among smokers is due to diseases not already established as caused by smoking; for example, renal failure, infections, and intestinal ischemia could potentially be linked to smoking.

Mortality among current smokers is 2 to 3 times as high as that among persons who never smoked. Most of this excess mortality is believed to be explained by 21 common diseases (12 types of cancer, 6 categories of cardiovascular disease, diabetes, chronic obstructive pulmonary disease, and pneumonia including influenza) that have been formally established as caused by cigarette smoking and are included in official estimates of smoking-attributable mortality in the United States.

Clinical Pearls

– Are current estimates of smoking-related mortality rates in the United States accurate?

The 2014 Surgeon General’s report estimates that cigarette smoking causes more than 480,000 deaths each year in the United States. This widely cited estimate of the mortality burden of smoking may be an underestimate, because it considers deaths only from the 21 diseases (mentioned above) that have been formally established as caused by smoking. Associations between smoking and the 30 most common causes of death in the United Kingdom in the Million Women Study suggest that the excess mortality observed among current smokers cannot be fully explained by these 21 diseases.

– Are there additional diseases that contribute to the excess mortality among current smokers in the United States?

In a prospective analysis, data were pooled from five contemporary U.S. cohort studies and included 421,378 men and 532,651 women 55 years of age or older. Participants were followed from 2000 to 2011.
During the follow-up period, there were 181,377 deaths, including 16,475 among current smokers. Overall, approximately 17% of the excess mortality among current smokers was due to associations with causes that are not currently established as attributable to smoking.
These included associations between current smoking and deaths from renal failure (relative risk, 2.0; 95% confidence interval [CI], 1.7 to 2.3), intestinal ischemia (relative risk, 6.0; 95% CI, 4.5 to 8.1), hypertensive heart disease (relative risk, 2.4; 95% CI, 1.9 to 3.0), infections (relative risk, 2.3; 95% CI, 2.0 to 2.7), and various respiratory diseases (relative risk, 2.0; 95% CI, 1.6 to 2.4).

Table 2. Relative Risks of Death from Specific Causes among Persons 55 Years of Age or Older, According to Sex and Smoking Status.

Morning Report Questions

Q: Is there an association between smoking and death from breast and prostate cancer?

A: In the analysis published in this week’s issue of the Journal, smoking remained significantly associated with death from breast cancer among women who were not current drinkers. However, associations between smoking and death from breast cancer may also be biased by differences in screening or treatment patterns among smokers, and information on these variables was not available in this study. Additional studies with detailed information on these factors may be useful in clarifying whether smoking is causally associated with death from breast cancer. Mortality from prostate cancer in this population was 43% higher among current smokers than among those who had never smoked, a finding that is consistent with most previous analyses of prostate-cancer mortality. The Surgeon General concluded that although there was insufficient evidence that smoking increases the incidence of prostate cancer, the available evidence suggested that current or recent smoking increases the risk of advanced-stage disease and of death from prostate cancer. Higher mortality from prostate cancer among smokers could be caused by delayed diagnosis owing to less intense medical surveillance or by a promoting effect of smoking on later stages of carcinogenesis and progression.

Table 3. Mortality and Excess Mortality, According to Sex and Smoking Status.

Q: To what extent does the 2014 Surgeon General’s report underestimate yearly deaths from smoking?

A: Results of this study suggest that the Surgeon General’s recent estimate of smoking-attributable mortality may have been an underestimate. The Surgeon General’s estimate, which took into account only the 21 diseases formally established as caused by smoking, was that approximately 437,000 deaths among adults are caused each year by active smoking (not including secondhand smoke).
However, the Surgeon General’s report presents an alternative estimate of 556,000 deaths among adults on the basis of the excess mortality from all causes. The difference between these two estimates is nearly 120,000 deaths. If, as suggested by the results in the cohort used in this study, at least half of this difference is due to associations of smoking with diseases that are causal but are not yet formally established as such, then at least 60,000 additional deaths each year among U.S. men and women may be caused by cigarette smoking.

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