Financial Conflicts of Interest and Stance on Tobacco Harm Reduction: A Systematic Review.

Background. Tobacco companies have actively promoted the substitution of cigarettes with purportedly safer tobacco products (e.g., smokeless tobacco, e-cigarettes) as tobacco harm reduction (THR). Given the tobacco, e-cigarette, and pharmaceutical industries' substantial financial interests, we quantified industry influence on support for THR. Objectives. To analyze a comprehensive set of articles published in peer-reviewed journals assessing funding sources and support for or opposition to substitution of tobacco or nicotine products as harm reduction. Search Methods. We searched PubMed, Embase, Web of Science, and PsycINFO with a comprehensive search string including all articles, comments, and editorials published between January 1, 1992, and July 26, 2016. Selection Criteria. We included English-language publications published in peer-reviewed journals addressing THR in humans and excluded studies on modified cigarettes, on South Asian smokeless tobacco variants, on pregnant women, on animals, not mentioning a tobacco or nicotine product, on US Food and Drug Administration-approved nicotine replacement therapies, and on nicotine vaccines. Data Collection and Analysis. We double-coded all articles for article type; primary product type (e.g., snus, e-cigarettes); themes for and against THR; stance on THR; THR concepts; funding or affiliation with tobacco, e-cigarette, pharmaceutical industry, or multiple industries; and each author's country. We fit exact logistic regression models with stance on THR as the outcome (pro- vs anti-THR) and source of funding or industry affiliation as the predictor taking into account sparse data. Additional models included article type as the outcome (nonempirical or empirical) and industry funding or affiliation as predictor, and stratified analyses for empirical and nonempirical studies with stance on THR as outcome and funding source as predictor. Main Results. Searches retrieved 826 articles, including nonempirical articles (21%), letters or commentaries (34%), editorials (5%), cross-sectional studies (15%), systematic reviews and meta-analyses (3%), and randomized controlled trials (2%). Overall, 23.9% disclosed support by industry; 49% of articles endorsed THR, 42% opposed it, and 9% took neutral or mixed positions. Support from the e-cigarette industry (odds ratio [OR] = 20.9; 95% confidence interval [CI] = 5.3, 180.7), tobacco industry (OR = 59.4; 95% CI = 10.1, +infinity), or pharmaceutical industry (OR = 2.18; 95% CI = 1.3, 3.7) was significantly associated with supportive stance on THR in analyses accounting for sparse data. Authors' Conclusions. Non-industry-funded articles were evenly divided in stance, while industry-funded articles favored THR. Because of their quantity, letters and comments may influence perceptions of THR when empirical studies lack consensus. Public Health Implications. Public health practitioners and researchers need to account for industry funding when interpreting the evidence in THR debates.