A recent study conducted by researchers systematically examined and consolidated the literature concerning the health hazards linked to chewing tobacco. Their findings reveal a notable increase in the likelihood of strokes and various cancers among individuals who chew tobacco. Although chewing tobacco is not as widespread as smoking cigarettes, it’s estimated that over 270 million individuals utilize smokeless tobacco products, predominantly in regions like India and Bangladesh. While smoking rates have decreased since the 1990s, the consumption of chewing tobacco appears to have risen, including among female users.
The health implications of chewing tobacco are not as comprehensively understood as the widely accepted consensus regarding the detrimental effects of cigarettes and other smoking methods. Nonetheless, smokeless tobacco is considered a carcinogen. In this research, scientists performed a systematic review and meta-analysis using data from three scientific databases (Global Index Medicus, Web of Science, and PubMed) to investigate the associations between chewing tobacco and stroke, ischemic heart disease, as well as five specific types of cancer affecting the neck and head.
The search encompassed publications from 1970 onwards, irrespective of language. Utilizing meta-regressions and Bayesian methods, researchers estimated a pooled relative risk measure and effect size for each health outcome. Out of the literature identified, 4,480 publications were excluded, leaving 111 for analysis.
Three studies from Bangladesh and India provided data on chewing tobacco and stroke. The meta-analysis indicated that the conservative estimate suggested a 16% increase in stroke risk associated with the use of smokeless tobacco products. This correlation is categorized as ‘weak’. However, these findings remained consistent across various validations, with no evidence of publication or covariate bias.
Eight studies investigated the links between smokeless tobacco and ischemic heart disease, with the majority conducted in Bangladesh, India, and the United States. The meta-analysis revealed no substantial evidence indicating that chewing tobacco significantly altered the risk of ischemic heart disease. Once again, researchers observed no indications of publication or covariate bias.
Regarding esophageal cancer, 22 studies were identified. Analysis indicated that the use of chewing tobacco resulted in a conservative 2% increase in cancer risk. However, employing a meta-analytic approach yielded a higher estimate of a 2.14-fold increase in esophageal cancer risk. The final analysis adjusted for smoking status, sex, and age, with no evidence of publication bias.
A comprehensive review of 70 studies investigated the connections between smokeless tobacco products and cancers affecting the lip and oral cavity. The analysis accounted for various sources of uncertainty and revealed a relative risk factor of 3.64. The association was classified as weak, with an increased risk of developing these cancer types observed, particularly in studies conducted in Asian countries.
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