Source: WebMD

Author: Marlene Busko

Lyon, France – Smokeless tobacco—such as snuff and chewing tobacco—is not harmless when it comes to heart health, according to a new meta-analysis [1]. A review of 11 studies from Sweden and the US, almost entirely in men, showed that smokeless-tobacco users had an increased risk of death from MI or stroke.

The study, by researchers at the International Agency for Research on Cancer(IARC), is published online August 18, 2009 in BMJ.

Contrary to common belief that smokeless tobacco has very little effect on health, these products have been shown to increase cancer risk, coauthor and IARC researcher Dr Kurt Straif (Lyon, France) told heartwire.

“There is sufficient evidence for a causal association between smokeless tobacco and oral and pancreatic cancer [2] and probably also esophageal cancer [3],” he said.

“Now, this study adds evidence that smokeless tobacco causes death from cardiovascular diseases,” Straif summarized.
Widespread, growing use of snus

Types of smokeless tobacco used in North America and Europe include dry snuff that is inhaled, as well as moist snuff (called snus in Sweden) and chewing tobacco (or spit tobacco), which are sucked inside the cheek.

These products have been around for centuries, and after a decline in consumption for most of the 20th century, use has rebounded in the past few decades, the authors write.

In 2000, 23.9% of men and 4.1% of women in Sweden reported using snus daily or occasionally. In the same year, in the US, 4.4% of men and 0.3% of women were current users of snuff or chewing tobacco.

To determine whether users of smokeless tobacco are at increased risk of death from MI or stroke, the researchers systematically reviewed worldwide studies published until 2009.

They then excluded studies from Asia, because the smokeless tobacco used there is a different type—generally betel quid, which contains other ingredients such as areca nut, Straif said.

The meta-analysis included eight studies from Sweden—where the use of snus is widespread—and three studies from the US. Ten studies were in men only, and apart from two studies, all were in people who had never smoked tobacco

Smokeless-tobacco use was linked with a greater risk of cardiac fatalities.

In eight studies, compared with nonusers, smokeless-tobacco users had a relative risk of fatal MI of 1.13 (95% CI 1.06-1.21).

Similarly, in five studies, compared with nonusers, smokeless-tobacco users had a relative risk of fatal stroke of 1.40 (95% CI 1.28-1.54)

Results were comparable in studies from Sweden and the US.

The researchers estimate that in 2000, 0.5% of deaths from MI and 1.7% of deaths from stroke in American men were due to smokeless-tobacco use.

Similarly, they estimate that in 2001, 5.6% of deaths from MI and 5.4% of deaths from stroke in Swedish men were due to smokeless-tobacco use.

The authors acknowledge that the review’s limitations include potential other confounders that were not accounted for.

However, “if the association [between smokeless tobacco and fatal cardiovascular outcomes] is real, its public-health and clinical implications might be substantial, despite the fact that the magnitude of the excess risk is small,” they write.

“Given the recent increase in use of smokeless tobacco, it is important to stress that all forms of tobacco are harmful and that the best prevention is not to start using any kind of tobacco, or—for users—to stop using all kinds of tobacco,” Straif said.
Baseball players and spitballs

In a comment to heartwire, AHA spokesperson Dr Nieca Goldberg (New York University School of Medicine, NY) said that most people know that smoking cigarettes is harmful, but they may not realize that smokeless tobacco also presents a health risk—for oral cancer, heart attack, and stroke.

Young people who watch baseball on television may be influenced by seeing baseball players who chew tobacco, she added.

“Cardiologists [and other physicians] need to remember to ask patients not only about cigarettes but also about smokeless tobacco,” she said

“The results are consistent with the INTERHEART study [4],” Dr Koon K Teo(McMaster University, Hamilton, ON), the lead author on that trial, toldheartwire. “We found that smokeless tobacco has been as harmful for heart attacks as smoking cigarettes.”