Does Smoking Really Cause Over 400,000 Deaths In
The United States?
The relative risks (RR) reported in the MMWR are based on smoking-related data from an unpublished American Cancer Society study called Cancer Prevention Study-II (CPS-II).
(1) The diseases listed on the MMWR are "known to be caused by or associated with smoking in adults," so says a report to Congress from the CDC's Office on Smoking and Health.
"Associated with" means "occurs together with." It does not imply causality. For instance, according to the Sudden Infant Death Syndrome Alliance, SIDS is associated with being born twins or triplets. This does not mean that being born twins or triplets causes SIDS.
Likewise, just because some of the diseases listed on the MMWR are associated with smoking (e.g., pneumonia and influenza) doesn't mean that smoking caused those deaths.
(2) Almost half of the relative risks reported in the MMWR are less than 2.
For example, under Cardiovascular Diseases, the relative risks for Ischemic Heart Disease for persons 65 years or older are: 1.9 (male current smokers), 1.3 (male former smokers), 1.7 (female current smokers), and 1.2 (female former smokers).
According to the National Cancer Institute, " ... relative risks of less than 2 are considered small and are usually difficult to interpret ... Such increases may be due to chance, statistical bias, or effects of confounding factors that are sometimes not evident." (NCI release, 10-26-94, as reported in the Competitive Enterprise Institute newsletter, CEI Update, February 1995, p.8).
Sir Richard Doll, one of the first researchers to report a link between active smoking and lung cancer, says that " ... when the relative risk lies between 1 and 2 ... problems of interpretation may become acute, and it may be extremely difficult to disentangle the various contributions of biased information, confounding of two or more factors, and cause and effect." (The Causes of Cancer," by Richard Doll, F.R.S. and Richard Peto. Oxford-New York, Oxford University Press, 1981, p. 1219).
(3) CPS-II did not consider confounding factors such as diet, alcohol, occupation, socioeconomic status, etc. Therefore, as stated in the MMWR, the estimates "in this report are not adjusted for confounders (e.g. alcohol), which may lower the estimates for laryngeal and certain upper gastrointestinal cancers." In other words, if confounders were considered, the estimates would no doubt be lower.
Dr. Ernst Wynder of the American Health Foundation says you have "clearly got to think about fat as a confounder to tobacco consumption." (The Toxicology Forum, Annual Summer Meeting, 1993. Given Institute of Pathobiology, Aspen, Colorado. Transcrip p. 308.
According to Dr. Wynder, smokers have a lower intake of fresh fruits and vegetables than nonsmokers, consume more fat and more red meat, and have a higher serum cholesterol because of the high fat intake.
Dr. Michael Siegel, who is employed in the CDC's Office on Smoking and Health, says that one of the most important things to consider in lung cancer risk is diet. (Michael Siegel, M.D., MPH, "Involuntary Smoking in the Restaurant Workplace, " JAMA, July 28, 1993, Vol. 270, No. 4, p. 492.
CDC's Ann Malarcher says that "many factors ... are causally related to cardiovascular disease ... They include, but are not limited to, cigarette smoking, hypertension, elevated serum cholesterol, obesity, genetics, diabetes, physical inactivity, socio economic status and diet." (Correspondence from Ann Malarcher, Ph. D., Epidemiologist, Office on Smoking And Health, CDC, September 25, 1995).
If "many factors" are causally related to cardiovascular disease, why did the CDC examine just one: smoking"
And if diet is one of the most important things to consider in lung cancer risk, as Dr. Michael Siegel and others say it is, why did the CDC not consider it"
How does the CDC know that smoking caused 1,294 deaths from cervical cancer if other risk factors such as early and frequent sexual intercourse, multiple sexual partners, pregnancy at an early age, and the presence of sexually transmitted diseases ( to name a few) were not considered"
CLICK HERE to see hypertexted MMWR chart.
The Morbidity and Mortality Weekly Report (MMWR) Series is prepared by the Centers for Disease Control and Prevention (CDC) and is available on a paid subscription basis from the Superintendent of Documents, U. S. Government Printing Office, Washington, DC 20402: telephone (202) 783-3238.
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