Summary of the epidemiological evidence relating snus to health
Introduction
Smokeless tobacco is used worldwide, but the products vary considerably. In parts of North Africa and Central and South-East Asia the tobacco is sometimes heavily roasted, often used with other products, such as betel nut, slaked lime and areca nuts (Critchley and Unal, 2003, International Agency for Research on Cancer, 2007a, Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR), 2008), and may contain high levels of carcinogenic nitrosamines (Idris et al., 1991, Stepanov et al., 2005) and other carcinogenic impurities, including significant quantities of polycyclic aromatic hydrocarbons (International Agency for Research on Cancer, 1985). The product used also varies between the USA and Sweden, the only North American and European countries where smokeless tobacco is commonly used (International Agency for Research on Cancer, 2007a). In the USA chewing tobacco is common, and moist and dry snuff are also used, but in Sweden a type of moist snuff known as snus is the dominant product (Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR), 2008). This review concentrates on the rapidly accumulating epidemiological evidence relating snus to health.
Swedish-type moist snuff (“snus”) consists of finely ground air- or sun-cured tobacco, salt (sodium chloride), water, humidifying agents, chemical buffering agents (sodium carbonate), and food-grade flavourings. In former years a pinch (or dip) was placed between the gum and upper lip, often for 11–14 h daily (International Agency for Research on Cancer, 2007a), but more recently the most common method of application by far is by portion-packed tobacco in small sachets. This change follows studies showing that use of pack products greatly reduces the risk of tobacco-related oral pathological changes (Andersson and Axéll, 1989, Axéll, 1993). Use of snus involves nicotine exposure similar to, and perhaps somewhat greater than, that from smoking (Agewall et al., 2002, Bolinder et al., 1997a, Bolinder et al., 1997b, Bolinder and de Faire, 1998, Eliasson et al., 1991, Holm et al., 1992, Wennmalm et al., 1991).
The potential carcinogenicity of smokeless tobacco products used in western countries is practically wholly associated with the presence of the tobacco specific nitrosamines (TSNA) NNK (4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone) and NNN (N′-nitrosonornicotine) (International Agency for Research on Cancer, 2007a, Nilsson, 1998). It should be noted that snus has, for several decades, been based on a low-nitrate tobacco that is neither fermented nor fire cured, giving very low levels of TSNA as well as of carcinogenic polycyclic aromatic hydrocarbons. Also, Swedish retailers refrigerate packages to prevent formation of TSNA during storage (International Agency for Research on Cancer, 2007a, Nilsson, 1998). Current levels of TSNA is snus are below 2 μg/g dry weight (Osterdahl et al., 2004).
Although selling snus is banned in other EU countries, Sweden has a special derogation due to its long history of use. In Sweden, the proportion of tobacco sold as snus (by weight) fell from 67% in 1925 to 19% in 1965, when use was concentrated in older men, but then rose, to 54% in 2005 (Forey et al., 2006–2009), with usage spreading to younger people (Nordgren and Ramström, 1990). Recent surveys report regular use by about 20% of males and 3% of females aged 15+ (Forey et al., 2006–2009). Compared with other West European countries, manufactured cigarette smoking in males is less common in Sweden (Table 1). Also, Sweden has a relatively low rate of major smoking-related diseases (Table 2), although it should be noted that inter-country comparisons are affected by other factors (e.g. alcohol consumption) and that Table 2 only considers an illustrative selection of countries. Foulds et al. (2003) have commented on the strikingly favourable lung cancer trend among Swedish (compared to Norwegian) men, accompanied by their increased use of snus and decreased smoking.
Recently, interest in snus as a possible safer alternative to smoking has risen, various reviews being published (Broadstock and 2007, 2007, Colilla, 2010, Critchley and Unal, 2003, Nilsson, 1998, Scientific Committee on Emerging and Newly Identified Health Risks (SCENIHR), 2008). These are often limited by not including meta-analyses, considering few health effects, failing clearly to separate effects of snus and other types of smokeless tobacco, omission of some recent relevant studies, and/or (as demonstrated later) inappropriately evaluating evidence on smoking initiation or cessation. Recently, my colleagues and myself have reviewed the evidence relating smokeless tobacco use in Europe and North America to cancer (Lee and Hamling, 2009a), oropharyngeal cancer (Weitkunat et al., 2007), pancreatic cancer (Sponsiello-Wang et al., 2008), circulatory disease (CID) (Lee, 2007) and oral disease (Kallischnigg et al., 2008). The current epidemiological evidence for these and other possible effects of snus is summarized in Sections 3.1 Cancer, 3.2 Non-neoplastic oral disease, 3.3 CID, 3.4 Diabetes, 3.5 Blood pressure, 3.6 Other risk factors for CID, 3.7 Respiratory system diseases, 3.8 Digestive system diseases, 3.9 All-cause mortality, 3.10 Pregnancy and reproductive effects, 3.11 Psychiatric disorders, 3.12 Neurodegenerative disorders, 3.13 Musculoskeletal disorders and other conditions, 3.14 General health, with data on the interrelationship of snus with smoking considered in Sections 3.15 Interrelationship of snus use and smoking, 3.16 Does snus use affect smoking initiation?, 3.17 Does snus use affect smoking cessation?. Attention is limited to evidence from Sweden and on occasion its neighbours. The intent is to provide an up-to-date, comprehensive summary of the main evidence relating to snus use as a possible alternative to smoking.
Section snippets
Materials and methods
For cancer and CID methods are as described previously (Lee, 2007, Lee and Hamling, 2009a), with searches updated to September 2010. Studies in Sweden, Norway, Denmark and Finland are considered. Random-effects meta-analyses (Fleiss and Gross, 1991) are restricted to relative risk (RR) or odds ratio (OR) estimates for snus use (ever vs. never or current vs. never) which are controlled for smoking, based either on whole population data adjusted for smoking, or data for never smokers.
Cancer
Three cohort studies report relevant results; the construction workers study (Bolinder et al., 1994, Fernberg et al., 2006, Fernberg et al., 2007, Luo et al., 2007, Odenbro et al., 2005, Zendehdel et al., 2008), the Norway cohorts study (Boffetta et al., 2005) and the Uppsala county study (Roosaar et al., 2008). Eight publications (Blomqvist et al., 1991, Hansson et al., 1994, Lagergren et al., 2000, Lewin et al., 1998, Lindquist et al., 1987, Rosenquist et al., 2005, Schildt et al., 1998, Ye
Possible health effects of snus
The evidence provides little support for the existence of any major adverse health effect of snus. Some associations are consistently demonstrated, but seem either of relatively minor consequence, or not necessarily causally related. Thus snuff-dipper’s lesion (Kallischnigg et al., 2008) does not predict oral cancer (Roosaar et al., 2006), and a reported acute effect of snus on blood pressure (Hirsch et al., 1992, Rohani and Agewall, 2004) is unsupported by evidence of increased blood pressure
Conclusions
Using snus is clearly much safer than smoking. While smoking substantially increases the risk of cancer and CID, any increase from snus use is undemonstrated, and if it exists is probably about 1% of that from smoking Even were isolated reports of some adverse health consequences of snus confirmed, switching to snus should improve the health prospects of those smokers who are unable or unwilling to relinquish nicotine. There is no good evidence that introducing snus in a population would
Conflict of interest
The author is a long-term consultant to the tobacco industry. However, this is an independent scientific assessment, the views expressed being those of the author alone.
Acknowledgments
This work (and the earlier reviews underpinning it) was supported by Philip Morris Products, Swedish Match, and the European Smokeless Tobacco Council. The study sponsors had no involvement in the planning, execution or writing of this manuscript or the decision to submit it for publication. Thanks are due to Rolf Weitkunat, Gert Kallischnigg, Zheng Sponsiello-Wang and Jan Hamling, co-authors of the earlier reviews, for permission to use the data included. Thanks are also due to Pauline
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2020, Food and Chemical ToxicologyCitation Excerpt :For several decades low-nitrate tobacco, that is neither fermented or fire cured has been used due to its low levels of TSNA's and polycyclic hydrocarbons (PAH's). Swedish snus is furthermore is refrigerated during storage to prevent formation of TSNAs (Fagerstrom and Schildt, 2003; Iarc, 2007; Lee, 2011). Tobacco-free ‘modern’ oral nicotine pouches (MOPs), are similar in appearance and use to Swedish-style snus, but without tobacco and therefore TSNA's, which may further reduce the risk to consumers.