Nicotine products relative risk assessment: an updated systematic review and meta-analysis

Abstract

Background: The nicotine products relative risk assessment estimates the relative risk of tobacco-related diseases due to use of 15 nicotine products. This update adds new data to the original analysis and creates separate categories for United States and rest of world varieties of smokeless tobacco, as well as bidi cigarettes. Methods: The PubMed®, MEDLINE and Clinicaltrials.gov databases were searched systematically. The study lists were exported, screened at the title, abstract and full-text level according to pre-defined inclusion/exclusion criteria. The study quality was assessed, and risk of bias was accounted for in the screening criteria. The extracted data was synthesized into a toxin emissions/content analysis for 12 Group 1 carcinogens, used to estimate lifetime cancer risk, and epidemiological meta-analysis of over 40 tobacco-related diseases. The two analyses were integrated into a combined risk score for each nicotine product, weighted by the risk of bias due to missing data, and incorporated into the relative risk spectrum. Results: In this update, 70 new studies were added to the synthesis, making a total of 123 studies included. All combustible tobacco products score between 40 and 100, with bidis and smokeless (rest of world) also in this range. All other products have a combined risk score of 10 or less, including U.S. chewing tobacco, U.S. dipping tobacco, snus, heat-not-burn tobacco, electronic cigarettes, non-tobacco pouches and nicotine replacement therapy. Discussion: Consistent with previous studies, we define a group of high-risk nicotine products, scoring between 40 and 100 on the spectrum, and reduced risk nicotine products, scoring less than 10. Limitations of this study include the potential for bias due to missing data, the heterogeneity of the data included in the relative risk hierarchy synthesis, and the assumed consumption levels.