ArticlesOral use of Swedish moist snuff (snus) and risk for cancer of the mouth, lung, and pancreas in male construction workers: a retrospective cohort study
Introduction
Use of snuff has become increasingly popular in several countries, but Sweden has the highest consumption, predominantly in the form of moist snuff (snus). The habit is especially gaining popularity in adolescents and women.1 At present, however, the majority of users are men; at least 23% of Swedish men used snus in 2002.2
About 30 carcinogens have been identified in smokeless tobacco, and the tobacco-specific nitrosamines, formed from nicotine and related tobacco alkaloids, are thought to be particularly important.3 The tobacco-specific nitrosamines with the greatest proportions in snuff (4-(nitrosomethylamino)-1-(3-pyridyl)-1-butanone [NNK] and N′-nitrosonornicotine [NNN]), have been implicated in the cause of tobacco-related cancers.4, 5, 6 Comparative studies have generally shown lower concentrations of tobacco-specific nitrosamines in Swedish snus than in American snuff,7 leading to a perception that the use of Swedish snus is a suitable alternative to smoking. Indeed, with a few exceptions,8, 9, 10 studies of Scandinavian snus have shown no risk associated with use of this form of tobacco.7 The Scandinavian experience differs from that in South Asia11 and elsewhere,12, 13 where smokeless tobacco is an established risk factor for oral cancer. This inconsistency might be attributable to methodological aspects, such as inadequate control for confounding by cigarette smoking and alcohol use, which are strong risk factors for oral cancer.
Because of NNK's specificity for the lung in rodent cancer models,14, 15 lung cancer should be another concern in relation to smokeless tobacco. However, few studies have addressed this risk in human beings. The only study of Scandinavian snus and lung cancer showed a non-significantly decreased risk in snus users,10 raising questions about residual confounding due to smoking. Epidemiological evidence10, 16, 17, 18 suggests that the use of smokeless tobacco, including Scandinavian snus,10 might increase the risk of pancreatic cancer, but published data are based on few snus-exposed cases.
With a growing awareness of the health hazards associated with smoking, snus could become increasingly popular,19, 20 and the habit might spread to people who would otherwise refrain from tobacco use. Therefore, valid and precise epidemiological data on health risks associated with use of snus are urgently needed. We consequently did a prospective study in Swedish construction workers, with a high prevalence of exposure to snus, to address the association of snus use with oral, lung, and pancreatic cancer.
Section snippets
Setting and participants
The background of the Swedish construction worker cohort has been described previously.21 Briefly, from 1969 through 1992, preventive health check-ups were offered to all workers in the Swedish building industry, and from 1971, the collected data were compiled in a computerised central register. Each record also contained the participant's National Registration Number, a unique personal identifier assigned to every Swedish resident at birth or immigration. This identifier includes the date of
Results
The figure shows the numbers of eligible workers included in and excluded from the group for our analysis. Characteristics of the 279 897 men in our cohort, including smoking and snus use, are shown in table 1. Average age at entry was 35 years (SD 13). These men were followed-up for an average of 20 years (SD 6). At time of entry, 31% of the cohort members used or had previously used snus. The proportion of ever-smokers was greater for men older than 30 years than in younger men, whereas snus
Discussion
The main finding of this large cohort study was an increased risk of pancreatic cancer in never-smoking snus users compared with never-users of any tobacco, with some evidence for a dose-risk association. We did not detect any excess risk for cancer of the oral cavity or lung.
Our finding is at odds with the perception that use of Swedish moist snus has no demonstrable carcinogenic risk.7 If valid, it will have important public-health implications, since snus has been proposed as a way to reduce
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