Thursday, October 21, 2010

Snus Users and Smokers in Stockholm

A new study published in Biomed Central Public Health (available here) describes the socioeconomic and lifestyle characteristics of snus users and smokers in Stockholm County, Sweden. Based on a 2006 survey of 35,000 residents, it was authored by Karin Engström and colleagues at the Department of Public Health Sciences at the Karolinska Institute. In addition to providing interesting information about snus users, this study has important implications for Karolinska Institute claims about the link between snus use and cancer.

Among men, 17% were exclusive snus users, 11% smoked and 2.4% were dual users. Among women, cigarette smoking was dominant (15%), while snus use and dual use were only 3.1% and 0.5% respectively. Given this, I will focus on the findings for men.

It is noteworthy that the prevalence of snus use was highest among men less than 35 years old. This means that young men in Stockholm strongly prefer snus, a lifestyle choice that will have little or no effect on their health as they age.

Snus users were somewhat more likely to have lower education levels than nonusers of tobacco, a trend that was even stronger among smokers. Smokers were also more likely to be unskilled and skilled workers in the very low income group, while snus users were more evenly distributed among all occupational classes and across all income levels.

One of the more interesting results concerned alcohol consumption. Risky alcohol consumption was defined as 14 standard drinks per week; the survey also asked about weekly or monthly binge drinking. Snus users and smokers were more likely to practice risky consumption than nonusers (odds ratios = 1.8 – 1.9), and they were more likely to have weekly binge-drinking episodes (ORs around 3.1).

This information on alcohol abuse among snus users is important, because a Karolinska epidemiology group, led by Olof Nyrén, published studies suggesting that snus use is associated with a small risk of pancreatic, stomach and esophageal cancer (abstracts here and here) among workers in the Swedish construction industry. Alcohol abuse is a strong risk factor for esophageal cancer and may be linked to stomach and pancreas cancer; this makes it a confounder with respect to snus use. In other words, if snus users are more likely to be alcohol abusers, then some of the cancers attributed to snus might instead be caused by alcohol. In many modern epidemiologic studies, standard procedures are used to account for confounders. In this case, to accurately separate the risks due to snus use from those due to alcohol abuse.

But the construction worker studies had no information on alcohol consumption, so alcohol abuse could not be ruled out as a competing risk factor. The lack of information about alcohol in these studies is a serious deficiency that raises questions about the validity of Nyrén’s claims.

In summary, men in Stockholm from all income levels and all occupations prefer snus over cigarettes. The impact of this preference on their health is so small that it is barely measurable by modern epidemiologic methods. Furthermore, snus users, like smokers, are more likely to abuse alcohol, which may be a distinct risk factor for some cancers that has not been evaluated in previous Karolinska Institute reports on snus use.


Carl V Phillips said...

Great analysis. It is too bad that the study used the wrong measure for dangerous alcohol consumption: For men 2 drinks/day is actually at the top end of the *ideal* alcohol consumption range, better for you than not drinking. At worst it is just into the range of "this is not very bad for you, though you would be slightly physically healthier if you pared it back a bit." That does not change your point since all heavy drinkers still fall into this category, it just makes a mess of it, mixing known healthy levels of the exposure with the unhealthy ones, and so is bad epidemiology.

On the topic of pancreatic Ca, FYI (I am not sure whether you saw a copy of this) Karyn Heavner and I presented an analysis that corrected some of the Karolinska numbers for effect of alcohol (based on estimates of the association between snus use and alcohol) at the Society for Epidemiologic Research meetings last year. Interestingly, someone who was representing for the U.S. government argued with our presentation on the basis that alcohol is no longer considered an important PC risk factor. I have not had a chance to form an opinion on that point -- just passing it on.


Chris Oakley said...

"Risky alcohol consumption was defined as 14 standard drinks per week"

Based on what evidence?

Anonymous said...

This is an interesting topic and a subject that I sought out specifically. As the author wonders whether the risks of snusing are overblown because of a non sequitar correlation to alcohol consumption. I posit that some people are more prone to cancers because of other unhealthy lifestyle choices.

I don't disagree that lack of internal drive or education are potential causes for this, but wonder how many can do things like drink and smoke cigarettes non-stop and then eat meats and vegetables from sources outside of the corporate grocery stores and continue on for years past the normal expected life span, not sure if that thought means anything to you. It does make me wonder ...