A systematic review of the epidemiologic literature on the health effects of smokeless tobacco (ST) and its relevance to the harm reduction model for smoking was undertaken. Published epidemiologic studies, from the US and European countries, meeting defined inclusion criteria and assessing the health effects of smokeless tobacco products were examined. ST use showed evidence of a slightly increased risk for all-cause mortality. Little evidence was found to support a causal relationship between ST use and risk of oral, pancreatic or lung cancer. ST use was not associated with an increased risk of cardiovascular disease or stroke incidence, but evidence suggested ST use was associated with increased mortality from these diseases. Clinical trials evaluating the effectiveness of ST products in smoking cessation have been sparse, and no standardized method for measuring ST dependence has been used, limiting the assessment of their relationship to ST use. Several studies have examined if ST use increases the risk of smoking initiation, but few have modeled this complex behavior appropriately. Overall, epidemiologic studies have not shown strong evidence of elevated tobacco-related disease risks with ST use. More research is necessary to assess the smoking behavioral consequences of ST use prior to its consideration as a harm reduction tool.
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