People who use Swedish moist snuff (snus) run twice the risk of developing cancer of the pancreas. This is the main result of a follow-up study conducted by Karolinska Institutet researchers amongst almost 300,000 male construction workers. The study is published today online in the prestigious medical journal The Lancet.
Tobacco smoking is a known risk factor for pancreatic cancer, which is an unusually malignant form of the disease. Since it is common for people who take snus - a tobacco product designed for insertion between the gum and upper lip - to also smoke cigarettes, the challenge facing epidemiological research into snus and cancer has been to isolate the effects of the different kinds of tobacco.
What makes this new study unique is that it has been possible to study the correlation between snus and cancer risk in a large enough group of men who have never smoked.
The subjects attended health check ups between 1978 and 1992, during which they were asked to report on their smoking and 'snusing' habits. The researchers have also studied rates of oral and lung cancer amongst the men, but found no correlation to snus.
"We're actually not that surprised," says project leader Professor Olof Nyrén of the Department of Medical Epidemiology and Biostatistics. "Pancreatic cancer has been under discussion in several earlier epidemiological studies on humans, both regarding Scandinavian snus and American smoke-free tobacco. On the other hand, previous studies of oral and lung cancer in relation to Scandinavian snus have been negative."
The main contribution of the new study is its conclusion that Swedish moist snus can be carcinogenic. However, the study also shows that the risks for users are small, and, as far as can be judged, much smaller than the risks associated with smoking.
"If 10,000 non-smoking snus users are monitored for ten years, according to our data, eight or nine of them will develop pancreatic cancer, as opposed to four amongst those who use neither product. But 9,991 won't, so the odds aren't that bad," he says.
The debate on whether the net effect of snus is positive or negative has been raging for many years. Some scientists and health carers have advocated the use of snus, as it is likely to lead to that people will smoke less. However, Professor Nyrén argues that it is important to have all the facts on the table before any advice can be given about snus as a way to cut down on smoking.
"We don't only need reliable and accurate measures of the risks of both smoking and taking snus, we also need know the effects of other, alternative methods to cut smoking. We also have to be certain that an increase in snus marketing will not cause addictions in young people who otherwise wouldn't have started to smoke," he says.