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Although less harmful than cigarette smoking, smokeless tobacco products are not safe as a smoking cessation tool and carry a number of potentially fatal health risks, an American Heart Association scientific statement said.

The review, published in the most recent issue of Circulation, analyzed numerous U.S. and international studies -- primarily those in Sweden, where the spitless tobacco pouch product snus is most popular -- that measured multiple health risks associated with cigarette smoke and compared smokeless tobacco users against nontobacco users.

The summary of evidence by Mariann R. Piano, PhD, of the Univesity of Illinois at Chicago, and colleagues found long-term smokeless tobacco users are at an increased risk for a fatal myocardial infarction, fatal stroke, some cancers, and oral disease. Studies completed in purely Swedish populations found use of moist snuff -- ground tobacco which is snorted -- increased odds of developing metabolic syndrome and type 2 diabetes.

Mortality related to heart disease and myocardial infarction was measured in three U.S. studies. Two studies noted increased fatality from coronary heart disease in smokeless tobacco users (HR 1.12, 95% CI, 1.02 to 1.21 and HR 1.25, 95% CI, 1.08 to 1.47). Another study did not find a significant increase in death associated with smokeless tobacco-related heart disease (HR 0.6, 95% CI, 0.3 to 1.2).

Stroke death risk was also measured in three U.S. studies, two of which found an increased danger in patients who exclusively used smokeless tobacco (HR 1.46, 95% CI, 1.31 to 1.64 and HR 1.40, 95% CI, 1.10 to 1.79). A third study found no increase in stroke incidence in snuff users (incidence rate ratio 1.07, 95% CI, 0.65 to 1.77), with a low number of fatal strokes associated with use.

Data from multiple studies failed to find a relationship between smokeless tobacco and hypertension, though it was noted cigarettes and smokeless products caused a significant increase in heart rate throughout the user's day.

One study compared life expectancies of 35-year-old smokers with smokeless product users and nonusers. Smokers averaged a life expectancy nearly eight years lower than those who used smokeless tobacco or did not use tobacco (28.1 years versus 35.9 years in the latter two groups). Smokeless tobacco users averaged a life expectancy 15 days shorter than a nonuser.

However, another study found that smokers who switched to smokeless tobacco from cigarettes had a higher rate of death from any cause than patients who stopped tobacco use.

Another element confounding the use of smokeless tobacco products as a smoking cessation tool is the possibility of nicotine withdrawal that is associated with quitting the alternative tobacco sources.

Smokeless tobacco products used in the U.S. include chewing tobacco, moist and dry snuff, compressed oral supplements, and snus. The review noted that Swedish snus differs from products sold by U.S. cigarette companies R. J. Reynolds Tobacco Company and Philip Morris USA due to changes in pH and production.

The authors concluded that follow-up research should investigate factors associated with the initiation and use of smokeless tobacco products; the extent to which the use of smokeless tobacco products influences continued overall tobacco use; and the effect of risk reduction messages on public perception and on tobacco use and cessation.