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Health risks of Swedish snus

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Illustrasjonsfoto: Nyebilder.no
Illustrasjonsfoto: Nyebilder.no

Swedish snus has several potential harmful effects and can also affect the foetus if used during pregnancy, according to a new report from the Norwegian Institute of Public Health.


The Ministry of Health and Care Services commissioned an update to the Institute’s 2014 report on the health risks of snus use. Newer studies support the conclusions of the previous report.

Snus use in Norway

Snus consumption in Norway has increased in recent decades, especially among young adults, and among young women in particular. Most users are ex-smokers but the proportion of snus users who have never smoked has increased over the past 15 years.

From 2016 to 2018, 33 per cent of men and 40 per cent of women had not smoked before starting snus. This is an increase from the period 2004 to 2006, when 23 per cent of men and 12 per cent of women who used snus had never smoked.

Health risks

Swedish snus is the main type of snuff used in Norway. Research about health risks associated with use in this report therefore apply to Swedish snus.

Based on our systematic reviews of research studies on users compared to non-users, knowledge about the ingredients nitrosamines and nicotine, animal studies, plus knowledge of harmful effects from other tobacco products, the report concludes with the following risk of health outcomes for Swedish snus:

  • Cancer:
    • Use will probably increase the risk of cancer of the oesophagus and pancreas, and will possibly increase the risk of cancer of the stomach and rectum.
    • It is possible that snus use increases mortality after a cancer diagnosis (all types of cancer combined).
  • Diabetes and metabolic syndrome:
    • High consumption will probably increase the risk of type 2 diabetes and metabolic syndrome.
  • Cardiovascular disease and high blood pressure:
    • The risk of dying in the weeks following a heart attack or stroke will probably increase, and it is possible that there is an increased risk of dying in the longer term after a stroke.
    • Snus use will probably increase the risk of high blood pressure.
    • It is possible that the risk of death after a heart attack is halved if snus use is stopped after the heart attack, compared to continuing to use snus.
  • Pregnancy:
    • If women use snus during pregnancy, there will probably be an increased risk of premature birth.
  • If women use snus during pregnancy, there is a possible increased risk of:
    • Stillbirth
    • Caesarean section.
    • The newborn is small for gestational age, has reduced birth weight, neonatal apnea, has oral cleft malformations, or has an increased amount of nicotine metabolites in the urine.
  • Other diseases and health outcomes:
    • It is possible that the use of snus increases the risk of psychosis, weight gain and obesity.
  • For many other health outcomes, there was insufficient information to conclude whether snus affects the risk, and in which direction.

Method

The best way to assess health risks is to conduct randomised controlled long-term studies on humans; this means that participating individuals are randomly allocated to a snus using group and a control group who do not use snus. Both groups are then followed up over time and the measured responses are compared. However, this is unethical since snus contains carcinogens. Observational studies, and preferably follow-up studies of groups over time (prospective cohort studies), are therefore the best available research design to assess the health risks for humans.

Norway and Sweden are the only countries within the EU / EEA area where snus is allowed to be sold. As a result, there are few studies on the health risks of snus, so it can be difficult to draw conclusions based on population studies alone. The conclusions of this report are based on a comprehensive assessment of general knowledge about snus and its ingredients.

The report contains an assessment of population studies using the GRADE method, knowledge about the snus ingredients nitrosamines and nicotine, animal studies as well as considering knowledge of harmful effects from other tobacco products.

About the GRADE method terminology

When health risks in population studies are summarised according to international standards for systematic reviews, we assess our confidence in the research findings using the GRADE method. This results in differences in terminology compared to previous reports on health risks from use of Swedish snus.

The table below illustrate the terminology we use after we have used the GRADE method to assess our confidence in the research. Our confidence is described as high, moderate, low or very low. (Explanations under the table)

GRADE terminology used in this report

GRADE

assessment

Studies

Statements

Comments

High

⨁⨁⨁⨁

RCTs that are well
conducted, or well
conducted observational
studies which are upgraded twice

Exposure leads to…

 

Moderate

⨁⨁⨁◯

RCTs which are
downgraded; observational studies which are upgraded

It is likely /probable that
the exposure leads to../
The exposure probably
leads to…

 

Low

⨁⨁◯◯

Observational studies,
or RCTS which are
downgraded twice

It is possible that the
exposure leads to../
The exposure possibly
leads to..  may lead to..

Most estimates from observational studies will be in this category.

 

 

Very low

⨁◯◯◯

Observational studies
which are downgraded
or RCTs which are
downgraded three times

We are uncertain if../
We do not know if the
exposure affects…

 

Explanation of terms in the table:

Exposure = exposed to snus in this case.

Estimate = the result of a study in the form of a statistical estimate.

GRADE = Grading of Recommendations Assessment, Development and Evaluation 
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2386626/

Downgrading (using five domains) and upgrading (three domains) is about whether the studies measure what they intend to measure in a credible way, how accurate the results are and whether increasing doses alters the results (dose-response).

Observational Studies: A group of people who have elected to use snus are compared to a group of people who have elected to not use tobacco products.