WHY REVIEW ARTICLES ON THE HEALTH-EFFECTS OF PASSIVE SMOKING REACH DIFFERENT CONCLUSIONS

Objective.-To determine whether the conclusions of review articles on the health effects of passive smoking are associated with article qual ity, the affiliations of their authors, or other article characteristi cs. Data Sources.-Review articles published from 1980 to 1995 were ide ntified through electronic searches of MEDLINE and EMBASE and from a d atabase of symposium proceedings on passive smoking. Article Selection .-An article was included if its stated or implied purpose was to revi ew the scientific evidence that passive smoking is associated with 1 o r more health outcomes. Articles were excluded if they did not focus s pecifically on the health effects of passive smoking or if they were n ot written in English. Data Extraction.-Review article quality was eva luated 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. Art icle 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 re ceived funding from or participated in activities sponsored by the tob acco industry. Other article characteristics were classified by one of the authors using predefined criteria. Data Synthesis.-A total of 106 reviews were identified. Overall, 37% (39/106) of reviews concluded t hat passive smoking is not harmful to health; 74% (29/39) of these wer e written by authors with tobacco industry affiliations. In multiple l ogistic regression analyses controlling for article quality, peer revi ew status, article topic, and year of publication, the only factor ass ociated with concluding that passive smoking is not harmful was whethe r an author was affiliated with the tobacco industry (odds ratio, 88.4 ; 95% confidence interval, 16.4-476.5; P<.001). Conclusions.-The concl usions of review articles are strongly associated with the affiliation s of their authors, Authors of review articles should disclose potenti al financial conflicts of interest, and readers of review articles sho uld consider authors' affiliations when deciding how to judge an artic le's conclusions.