Smokeless tobacco: CV risks lower than cigarette smoking, but danger for disease remains

Piano MR. Circulation. 2010;doi:10.1161/CIR.0b013e3181f432c3.

CV risks were lower in those who used smokeless tobacco products instead of cigarettes, but there was still an increased risk for CVD, including fatal MI and stroke. These findings led the American Heart Association to publish a statement in which the organization would not endorse nor recommend smokeless tobacco as an alternative to cigarette smoking or as a smoking cessation product.

In the Scientific Statement appearing in Circulation, Piano and colleagues, on behalf of AHA, performed a meta-analysis on the CV risk associated with various forms of smokeless tobacco (ST), including snuff and chewing tobacco. They also set out to provide clarification as to whether ST products should be recommended to smokers instead of cigarettes to reduce the morbidity and mortality associated with smoking and to enhance smoking cessation.

Currently, ST products are used by an estimated 8.1 million individuals of all ages in the U.S. In their article, the researchers wrote that, similarly to cigarette smoking (CS), nicotine is the principal alkaloid present in ST products, although the amount varies significantly from product to product. Although regular uses of ST products take in an equal amount of nicotine per day as cigarette smokers, a major difference between the two is that nicotine inhaled via CS is absorbed quickly in the lungs, which then continues in high concentrations into the arterial circulation, and then to the heart, brain and other organs. Conversely, the absorption rate of nicotine from ST is much slower, with absorption continuing for 30 minutes or more.

They said the finding is relevant because the speed of absorption and maximum arterial blood levels achieved are determinants of the acute CV effects of nicotine. “More rapid absorption of nicotine is associated with greater heart rate acceleration,” the researchers said. “Thus … it is likely that the same daily dose of nicotine from CS would cause more injury than from ST.”

Relationship of ST to disease

To determine the CV risks associated with ST products, researchers performed a thorough, comprehensive search in PubMed and Cochrane Library databases for systematic reviews and meta-analyses related to this topic. They included English-language studies of adult men and women at least 18 years of age, most of which were conducted in the U.S. and Sweden.

Some of the highlights of their research included:

• Most studies indicated no increased incidence or prevalence of hypertension in ST product users.
• No significant increase in risk for nonfatal or fatal MI with ST product use, with the exception of one meta-analysis and one long-term follow-up study that indicated a modest increased risk of fatal MI and the INTERHEART study that showed an increased risk for acute MI.
• A slight increased risk for stroke mortality in ST product users.
• An association between ST product use and dyslipidemia.

One of the key differentiations between CS and ST product use that may explain why CS results in more severe CV events is that the direct oxidants believed to be the class of chemicals contributing most to CS-induced CVD are not an issue in ST products, the researchers reported.

However, the potential risks involved with ST product use should not be underestimated, they added.

“Data from two studies have shown that young nonsmoking men who were ST product users were two to three times more likely to become active cigarette smokers,” the researchers wrote. Although two other studies showed little relationship between ST product use and smoking initiation, they said there is concern that the younger population may be lulled into a false sense of security by turning to potential reduced-exposure or ST products.

“There also is concern that marketing one tobacco product as a substitute for others will divert attention from the smoking cessation message,” the researchers said.

AHA’s final stance

With all of the evidence presented on the role of ST products in CVD, the researchers made the following statement on behalf of AHA:

“As a national nonprofit health organization committed to promoting tobacco control research and policy efforts, the AHA does not recommend the use of ST as an alternative to CS or as a smoking cessation product. Although the evidence is consistent with the suggestion that the CV risks are lower with ST products, ST products are not without harm. … Furthermore, the promotion of ST may lead to fewer people quitting smoking and more dual use of cigarettes and ST products.”

As a way to limit the harmful effects of ST products, the researchers recommended prioritizing strategic efforts to evaluate factors associated with the initiation and use of ST products; determine to what extent the use of ST products results in continued tobacco use, including dual smoking and ST product use, in smokers who would otherwise have quit; and assess the effect of “reduced risk” messages related to ST products on public perception, tobacco use and cessation, and policy decision-making.

Based on their findings, they concluded, “Clinicians should continue to discourage use of all tobacco products and emphasize the prevention of smoking initiation and smoking cessation as primary goals for tobacco control.” – by Brian Ellis

For more information:

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• Substance Abuse and Mental Health Services Administration (SAMHSA). Results from the 2008 National Survey on Drug Use and Health: National Findings. Rockville, Md: SAMHSA, Office of Applied Studies; 2009.
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