Published online Jun 28, 2022. doi: 10.13105/wjma.v10.i3.130
Peer-review started: February 10, 2022
First decision: April 13, 2022
Revised: April 25, 2022
Accepted: May 28, 2022
Article in press: May 28, 2022
Published online: June 28, 2022
Processing time: 144 Days and 20.1 Hours
While extensive information exists relating cigarette smoking to the risk of lung cancer, chronic obstructive pulmonary disease (COPD), ischaemic heart disease (IHD) or acute myocardial infarction (AMI), and stroke, far less information is available on risks from moist snuff (“snus”) or smokeless tobacco (ST) in United States/Canada, Europe or Japan.
To summarize data from the selected countries on risks of the four diseases associated with current ST or snus use.
Publications in English in 1990-2020 were considered that, based on epidemiological studies in North America, Europe or Japan, estimated risks of lung cancer, COPD, IHD/AMI, or stroke according to use of ST or snus. The studies should involve at least 100 cases of the disease considered, and not be restricted to those with specific other diseases. Medline literature searches were conducted, selecting papers initially from examination of titles and abstracts, and then from full texts. Further papers were sought from reference lists in selected papers, reviews and meta-analyses. For each disease, relative risk estimates adjusted at least for age were extracted relating ST or snus use to risk, and combined using random-effects meta-analysis. The estimates were mainly for current vs. never or non-current use, but results for ever vs never use were also considered.
Seven publications reported results for ST use from six United States studies. The most useful results came from four studies which provided results for current vs. never use. Random-effects meta-analyses of these results showed an increased risk for each disease, clearest for lung cancer (relative risk 1.59, 95% confidence interval 1.06-2.39, based on 4 estimates) and COPD (1.57, 1.09-2.26, n = 3), but also significant (at P < 0.05) for IHD (1.26, 1.10-1.45, n = 4) and stroke (1.27, 1.03-1.57, n = 4). Also including results for ever vs. never use from two other studies increased the lung cancer estimate to 1.80 (1.23-2.64, n = 6), but had little effect on the other estimates. For snus, 16 publications described results from 12 studies, one in Norway and the rest in Sweden. There were no results for COPD, and only three for lung cancer, with these reporting a relative risk of 0.80 (0.40-1.30) for current vs never use. More extensive data were available for IHD/AMI and stroke. Using the latest results from each study, combined estimates for current vs. never use were 1.00 (0.91-1.11, n = 5) for IHD/AMI and 1.05 (0.95-1.17, n = 2) for stroke, while for current vs. non-current use they were 1.10 (0.92-1.33, n = 9) for IHD/AMI and 1.12 (0.86-1.45, n = 9) for stroke. Meta-analyses including earlier results from some studies also showed no significant association between snus use and IHD/AMI or stroke. No relevant results were found for Japan.
Risks of smoking-related diseases from snus use in Scandinavia are not demonstrated, while those from ST use in the United States are less than from smoking.
Core Tip: United States studies show that, in never users of other products, current smokeless tobacco use associates with a significant (P < 0.05) increase in risk of the four major smoking-related diseases, with relative risks, compared to never users, of almost 1.6 for lung cancer and chronic obstructive pulmonary disease (COPD) and 1.3 for ischaemic heart disease (IHD)/acute myocardial infarction (AMI) and stroke. This increase is substantially less than for smoking. In Scandinavia, current snus use, does not significantly increase risk of IHD/AMI, stroke or lung cancer, with no data for COPD. Smokers unwilling to quit might consider these smokeless products.