Deaths due to smoking in the US may be under-estimated.
The American Cancer Society (ACS) funded study suggests estimates from the Surgeon General that show smoking kills about 480,000 people in the US every year, exclude tens of thousands of Americans who die from diseases not counted as caused by smoking but perhaps should be.
For their analysis the researchers at the ACS reviewed data from 5 large studies, including the ACS Cancer Prevention Study-II, the Health Professionals Follow-up Study, the Nurses' Health Study, and the National Institutes of Health AARP Diet and Health Study.
The data covers nearly a million Americans aged 55 and over that were followed for about 10 years, during which time there were over 180,000 deaths, including nearly 16,500 among current smokers.
As expected, the analysis showed current smokers were nearly three times more likely to die in that time than people who never smoked.
Most of the excess deaths in smokers were due to diseases that are known to be caused by smoking.
These include 12 types of cancer, stroke, coronary heart disease and chronic obstructive pulmonary disease (COPD - which includes chronic bronchitis, emphysema and chronic obstructive airways disease).
Smokers had double risk of death from diseases not classed as caused by smoking
However, the research team also found that around 17% of the excess deaths in current smokers were attributed to diseases outside of the list of 21 that the US Surgeon General classes as caused by smoking and so are excluded in official estimated US deaths due to tobacco use.
Fast facts about smoking
- Tobacco use is the leading preventable cause death worldwide
- Smoking and tobacco use costs the US $289 billion a year, including more than $156 billion in lost productivity
- In 2011, the tobacco industry spent nearly $23 million a day on promoting and advertising cigarettes.
The investigators drew particular attention to where there they found a double risk of death among current smokers due to diseases such as intestinal ischemia (narrow or blocked arteries in the gut), kidney failure, infections, hypertensive heart disease and various types of respiratory disorders outside of COPD.
The authors note that even though these diseases are not officially regarded as being a result of smoking, and are therefore excluded from estimates of smoking-related deaths, there is strong evidence to suggest they are.
Their analysis also showed that excess risk of death from each of these conditions fell when participants gave up smoking.
The research team found smoking was also tied to smaller increases in risk of death from breast cancer, prostate cancer and cancers of unknown sites. These diseases are currently not formally classed as being caused by smoking.
The authors conclude that the number of additional deaths potentially linked to smoking is significant and may be due to diseases not formally established as caused by smoking.
However, should future research show they are, then they should be included in estimates of the death toll from tobacco use.
The study only covered data on one million people taking part in large studies.
"If the same is true nationwide, then cigarette smoking may be killing about 60,000 more Americans each year than previously estimated, a number greater than the total number who die each year of influenza or liver disease."
Meanwhile, another team of researchers reported that colorectal cancer survivors who smoke have twice the risk of death of their non-smoking counterparts. While they did not examine the biology behind the findings, the researchers suggested that perhaps smokers have more aggressive tumors, or that smoking may interfere with cancer treatment.
References:
1.
Smoking and mortality - beyond established causes, Brian D.
Carter, et al., N
Engl J Med, doi:10.1056/NEJMsa1407211, published online 12 February
2015, abstract.
2.
American Cancer Society news
release, accessed 12 February 2015.
3.
CDC Smoking & tobacco use: fast facts, accessed 12
February 2015.
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