Study Finds Chewing Tobacco Increases Risk of Stroke and Cancer

A new study published in the journal Nature Communications has revealed that chewing tobacco significantly increases the risk of stroke and several types of cancer, especially in the head and neck region. The study is the first to systematically review and synthesize the literature on the health effects of chewing tobacco, which is used by more than 270 million people worldwide, mostly in India and Bangladesh.

The researchers conducted a meta-analysis of 103 studies published from 1970 to 2023, covering seven health outcomes: stroke, ischemic heart disease, and cancers of the lip and oral cavity, esophagus, nasopharynx, other pharynx, and larynx. They used a Burden of Proof meta-analysis to generate conservative risk estimates, and adjusted for smoking status, sex, and age. They also assessed the quality and bias of the studies, and performed sensitivity and subgroup analyses.

The results and the implications

The study found that chewing tobacco was associated with a weak-to-moderate increase in the risk of stroke, lip and oral cavity cancer, esophageal cancer, nasopharyngeal cancer, other pharyngeal cancer, and laryngeal cancer. The pooled relative risk estimates ranged from 1.16 for stroke to 3.64 for lip and oral cavity cancer. No significant association was found between chewing tobacco and ischemic heart disease.

The study also found that the risk estimates varied by region, type, and amount of chewing tobacco, and by the type of control group used in the studies. The highest risk estimates were observed for studies conducted in India and Bangladesh, where chewing tobacco is most prevalent and diverse. The lowest risk estimates were observed for studies conducted in the US and Europe, where chewing tobacco is less common and standardized.

The study has important implications for public health and policy, as it provides evidence of the harmful effects of chewing tobacco, which is often overlooked or underestimated compared to smoking. The study also highlights the need for more high-quality research on the association between chewing tobacco and other types of head and neck cancers, such as nasopharyngeal and laryngeal cancer, which are less studied and less understood.

The recommendations and the limitations

The study recommends that chewing tobacco users should be advised and encouraged to quit, and that non-users should be warned and discouraged from starting. The study also recommends that chewing tobacco should be regulated and taxed, and that its production and marketing should be controlled and monitored. The study also suggests that chewing tobacco should be included in the global tobacco control efforts, such as the Framework Convention on Tobacco Control (FCTC).

The study acknowledges some limitations, such as the heterogeneity and variability of the studies, the exposure definitions, and the chewing tobacco products. The study also acknowledges the potential confounding and modifying factors, such as alcohol consumption, betel quid chewing, and genetic susceptibility. The study calls for more standardized and harmonized methods and measures for studying chewing tobacco and its health effects.

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