From the Department of Public Health Biology and Epidemiology, School of Public Health, University of California, Berkeley (Ms Barnes), and the Institute for Health Policy Studies, School of Medicine, and the Department of Clinical Pharmacy, School of Pharmacy, University of California, San Francisco (Dr Bero). Ms Barnes was a research associate at the Institute for Health Policy Studies, University of California, San Francisco, during the time this study was conducted.
Objective.— To determine whether the conclusions of review articles on the health
effects of passive smoking are associated with article quality, the affiliations
of their authors, or other article characteristics.
Data Sources.— Review articles published from 1980 to 1995 were identified through
electronic searches of MEDLINE and EMBASE and from a database of symposium
proceedings on passive smoking.
Article Selection.— An article was included if its stated or implied purpose was to review
the scientific evidence that passive smoking is associated with 1 or more
health outcomes. Articles were excluded if they did not focus specifically
on the health effects of passive smoking or if they were not written in English.
Data Extraction.— Review article quality was evaluated by 2 independent assessors who
were trained, followed a written protocol, had no disclosed conflicts of interest,
and were blinded to all study hypotheses and identifying characteristics of
articles. Article conclusions were categorized by the 2 assessors and by one
of the authors. Author affiliation was classified as either tobacco industry
affiliated or not, based on whether the authors were known to have received
funding from or participated in activities sponsored by the tobacco industry.
Other article characteristics were classified by one of the authors using
Data Synthesis.— A total of 106 reviews were identified. Overall, 37% (39/106) of reviews
concluded that passive smoking is not harmful to health; 74% (29/39) of these
were written by authors with tobacco industry affiliations. In multiple logistic
regression analyses controlling for article quality, peer review status, article
topic, and year of publication, the only factor associated with concluding
that passive smoking is not harmful was whether an author was affiliated with
the tobacco industry (odds ratio, 88.4; 95% confidence interval, 16.4-476.5; P<.001).
Conclusions.— The conclusions of review articles are strongly associated with the
affiliations of their authors. Authors of review articles should disclose
potential financial conflicts of interest, and readers of review articles
should consider authors' affiliations when deciding how to judge an article's
Barnes DE, Bero LA. Why Review Articles on the Health Effects of Passive Smoking Reach Different Conclusions. JAMA. 1998;279(19):1566-1570. doi:10.1001/jama.279.19.1566