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Chewing tobacco linked to higher stroke and cancer risk, study finds

In a recent study within the journal Nature Communications, researchers systematically reviewed and synthesized the literature on the health risks related to chewing tobacco. Their results indicate that folks who chew tobacco are significantly more more likely to suffer from strokes and several other cancers.

While chewing tobacco is just not as prevalent as smoking cigarettes, estimates suggest that greater than 270 million people use smokeless tobacco products, of whom the bulk live in India and Bangladesh. Smoking has declined because the Nineties, while the recognition of chewing tobacco appears to have increased, including amongst women.

The health risks of chewing tobacco are less understood in comparison with the just about universal consensus on the harms attributable to cigarettes and other types of smoking. Nevertheless, smokeless tobacco is regarded as a carcinogen.

Study: Health effects related to chewing tobacco: a Burden of Proof study. Image Credit: / Shutterstock

Concerning the study

On this study, researchers conducted a scientific review and meta-analysis across three scientific databases (Global Index Medicus, Web of Science, and PubMed) to investigate relationships between chewing tobacco and stroke, ischemic heart disease, and five kinds of cancer of the neck and head.

The search included publications no matter their language and papers published from 1970 onwards. They used meta-regressions and Bayesian methods to estimate a measure of pooled relative risk after which obtained an effect size for every health consequence. Of the literature obtained from the search, 4,480 were excluded, and 111 were included within the evaluation.


Three studies conducted in Bangladesh and India included data on chewing tobacco and stroke; the meta-analysis suggested that conservatively, using smoking tobacco products increased the chance of stroke by 16%. This association is classed as a ‘weak’ relationship. Nevertheless, these findings were robust to varied validations; no publication or covariate bias was detected.

Eight studies examined associations between smokeless tobacco and ischemic heart disease, most of which were conducted in Bangladesh, India, and america. The meta-analysis found no evidence that chewing tobacco significantly modified ischemic heart disease risk; again, researchers found no evidence of publication bias or covariate bias.

For esophageal cancer, 22 studies were identified; evaluation suggested that using chewing tobacco significantly increased the chance of cancer by 2% conservatively. Nevertheless, a meta-analytic approach yielded a better estimate of a 2.14-fold increase in esophageal cancer risk. Smoking status, sex, and age were adjusted for in the ultimate evaluation, and no publication bias was detected.

A complete of 70 studies examined associations between smokeless tobacco products and cancers of the lip and oral cavity. The evaluation incorporated quite a few sources of uncertainty and located a relative risk factor of three.64, and the association was characterised as weak; the chance of developing these types of cancer increased when the sample was restricted to studies conducted in Asian countries.

The effect size for laryngeal cancer was estimated from 24 studies. Researchers found that evidence regarding this consequence was weak after accounting for sources of uncertainty, while the relative risk factor was 2.66. Nevertheless, for a single study, the connection between smokeless tobacco and laryngeal cancer was significantly higher.

17 studies were included for nasopharyngeal cancer, and weak evidence of a relationship with a relative risk measure of two.50 was seen. Age and sex were included within the model after covariate selection, and no evidence of publication bias was found.

The consequence included within the meta-analysis was other cancers of the pharynx; data for this model was obtained from 31 studies. The relative risk factor was 2.33, and the association was characterised as weak. Nevertheless, using a subset of the info, a better risk measure of 4.38 was found, showing a stronger association.


The study had various strengths, including reducing the impact of geographical variation. Of the seven health outcomes included, six showed not less than weak evidence of increased risk faced by smokeless tobacco users; the one consequence for which no evidence was found was ischemic heart disease. The very best risks were of stroke and esophageal cancer, with a conservative estimate suggesting a rise in incidence of 2-16%.

A vital conclusion was that while chewing tobacco is taken into account a carcinogen, the literature predominantly examined its relationship with lip, oral cavity, and esophageal cancer, highlighting the necessity for more high-quality studies on associations with other cancers of the top and neck. Specifically, nasopharyngeal and laryngeal cancer also needs to merit careful remark in the long run, as should stroke.

Limitations of the study included the variability of smokeless tobacco products, exposure definitions, and geographical settings. The approach followed on this study was also not capable of estimate dose-response relationships. Nevertheless, these findings could be utilized by public medical examiners to raised counsel clients on harms related to smoking tobacco products and advocate for simpler public health policies, while they can also be of interest to community awareness campaigns.

Journal reference:

  • Health effects related to chewing tobacco: A Burden of Proof study. Gil, G.F., Anderson, J.A., Aravkin, A., Bhangdia, K., Carr, S., Dai, X., Flor, L.S., Hay, S.I., Matthew, M.J., McLaughlin, S.A., Mullany, E.C., Murray, C.J.L., O’Connell, E.M., Okereke, C., Sorensen, R.J.D., Whisnant, J., Zheng, P., Gakidou, E. Nature Communications (2024). 10.1038/s41467-024-45074-9,
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