 |
|
Why Review Articles on the Health Effects of Passive Smoking Reach Different Conclusions
Deborah E. Barnes, MPH;
Lisa A. Bero, PhD
JAMA. 1998;279:1566-1570.
ABSTRACT
| |
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 predefined criteria.
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 conclusions.
INTRODUCTION
THE US Environmental Protection Agency (EPA),1 the US Surgeon General,2 the National Research Council/National Academy of Sciences,3 and the International Agency for Research on Cancer4 have all reviewed the scientific evidence regarding the health effects of exposure to environmental tobacco smoke, and they have all concluded that passive smoking increases the risk of diseases such as lung cancer in adults and respiratory disorders in children. Several more recent reviews have found that passive smoking is also associated with an increased risk of heart disease5-6 and with sudden infant death syndrome.7 However, many review articles published in the scientific literature have concluded that passive smoking is not harmful to health.8 Given that a clinician might rely on a single review article to provide an accurate and up-to-date overview on a topic of interest, it is somewhat disconcerting that not all published review articles are reaching the same conclusion about the health effects of passive smoking, particularly when there is consensus in the scientific community that passive smoking is harmful. The goal of this study was to identify factors that might explain why review articles on the health effects of passive smoking are reaching different conclusions.
Several interrelated factors may influence the conclusions of review articles. First, the conclusions of review articles may vary depending on the quality of the review conducted. Review article quality is generally measured in terms of the degree to which a systematic strategy has been used to evaluate the evidence on a particular topic.9-15 It is generally believed that reviews that have been conducted systematically are less likely to reach biased conclusions than those that have not.9, 11, 15-16 For example, Antman et al9 found that, for reviews of myocardial infarction treatment, the conclusions of unsystematic reviews were often inaccurate and out-of-date when compared with a systematic review.9 Therefore, in the literature on passive smoking, review articles may be reaching different conclusions depending on their quality.
Another factor that may influence the quality of review articles, and therefore their conclusions, is whether they have been subject to peer review. Research conducted by us and by others has found that, for original research articles, the quality of articles published in peer-reviewed journals is superior to the quality of articles published in non–peer-reviewed symposium proceedings.17-18 It is therefore possible that the quality of review articles also differs depending on whether they have been peer reviewed, and this difference in quality may lead to differences in conclusions.
Article conclusions may also be influenced by sources of funding or author affiliations. Several studies have found that, for a wide range of industries, publications based on industry-funded research tend to draw pro-industry conclusions.19-24 Similarly, studies have found that authors of review articles tend to draw conclusions that are consistent with their professional affiliations.25-26 In the literature on passive smoking, it is therefore plausible that review article conclusions would be associated with tobacco industry sponsorship or tobacco industry–affiliated authors.
The specific topic of a review may also play a role in what conclusion is reached. For example, it is possible that passive smoking is truly associated with lung cancer and heart disease in adults, but not with brain tumors in children. One would therefore expect review articles on these different topics to reach different conclusions about the health effects of passive smoking.
Finally, one might expect the year of publication of a review article to be associated with its conclusion. For example, a review article published during the mid 1980s would be based on fewer original research articles than one published today, and it therefore might be less likely to reach a firm conclusion about the health effects of passive smoking.
The goal of our study was to evaluate the quality of review articles on the health effects of passive smoking and to determine whether the conclusions of review articles are primarily associated with their quality or with other article characteristics. Our a priori hypotheses were that review articles concluding that passive smoking is not harmful would tend to be poor in quality, published in non–peer-reviewed symposium proceedings, and written by investigators with tobacco industry affiliations. We also examined the topic of the review and the year of publication as potential confounding factors.
METHODS
Article Identification
Review articles on the health effects of passive smoking were identified by searching MEDLINE and EMBASE from 1980 through 1995 using a variety of key words and subject headings related to passive smoking and review and meta-analysis. The search strategy was developed in consultation with a librarian and was based on the strategy used by the Cochrane Collaboration, an international group dedicated to conducting systematic reviews of the biomedical literature.27 Additional review articles were identified from a database of symposium articles on passive smoking that had been gathered for a previous study.8 These articles were originally identified by searching MEDLINE, CATALOG, DIALOG, Conference Papers Index, TOXLINE, and International Guide to Periodicals from 1965 through 1993 for symposium proceedings related to passive smoking; in addition, 2 symposia were identified through Tobacco Institute press releases.
An article was included if it met the following criteria: (1) its stated or implied purpose was to review the scientific evidence suggesting that passive smoking is associated with 1 or more health outcomes; (2) it focused specifically on the health effects of passive smoking, rather than reviewing several causes of a particular disease; (3) it was written in English; and (4) it was published between 1980 and 1995. An article was excluded if it reviewed aspects of passive smoking other than health, such as exposure assessment or policy issues; if it discussed several different risk factors for disease, rather than focusing on the effects of passive smoking; or if it was an editorial, commentary, or letter to the editor. A total of 106 articles that satisfied these inclusion and exclusion criteria were identified.
Quality Assessment
We hired 2 independent assessors, both of whom had experience conducting systematic reviews, to evaluate the quality of the review articles identified. Assessors were trained to use our quality assessment instrument and were provided with a comprehensive set of instructions for use during the study. Quality assessors were blinded to our study hypotheses and were told that the sole purpose of the study was to evaluate the quality of review articles on the health effects of passive smoking. In addition, assessors were blinded to all identifying characteristics of the articles: author names and affiliations, journal titles, acknowledgments, and dates of publication were removed completely. Articles were sent to assessors in a random order using a random number generator on a computer. Assessors stated that they had never been affiliated in any way with either the tobacco industry or tobacco control groups and that they had not previously reviewed the literature on passive smoking.
Review article quality was evaluated using a slightly modified version of the Oxman instrument, which is the only instrument available for assessing review article quality that has been published and tested for validity and reliability.28-29 The criteria used to evaluate review article quality are listed in Table 1: items 2 through 9 and item 12 were based on the Oxman instrument. Items 1, 10, and 11 were added because they have been used by other researchers to evaluate the quality of reviews.10-11,25, 30
|
|
|
|
Table 1.—Criteria Used to Evaluate Quality of Review Articles on the Health Effects of Passive Smoking
|
|
|
For each criterion, the quality assessor could answer yes (2 points), partial (1 point), no (0 points), or can't tell (0 points), and the quality score was the number of points awarded divided by 24, the total number of points possible. The quality score could therefore have ranged from 0 (lowest) to 1 (highest).
Analyses were based on the mean quality score (the average of the 2 assessors' scores). If the assessors' scores differed by more than 1 SD (0.20 point), they were asked to discuss their answers until they achieved consensus, and the consensus score was used. Seventeen percent (18/106) of the articles were reevaluated using this consensus process. Agreement between reviewers was evaluated using the method proposed by Bland and Altman.31 The median difference between reviewers' scores was 0, and the 2.5%, 25%, 75%, and 97.5% quantiles were -0.21, -0.04, 0.13, and 0.21, respectively. This means that 95% of the time, reviewers' scores were within 0.21 of each other (approximately 1 SD), on a scale from 0 to 1. The correlation between the 2 reviewers' scores was 0.87.
Article Conclusions
Articles were classified as concluding that passive smoking is either harmful or not harmful. The conclusion was classified as harmful if the authors stated that passive smoking was definitely or probably harmful. The conclusion was classified as not harmful if the authors stated that passive smoking was definitely or probably not harmful, that the statistical association between passive smoking and adverse health outcomes was attributable to poor study design or bias, or that the evidence was inconclusive. Articles concluding that the evidence was inconclusive were classified in the not harmful category because this conclusion is consistent with an acceptance of the null hypothesis that there is no relationship between passive smoking and disease.
Article conclusions were classified independently by the 2 quality assessors, who were blinded to study hypotheses and all identifying aspects of the articles, and by one of us (D.E.B.), who was blinded to article quality scores. Interrater agreement was excellent: all 3 raters agreed on the conclusion category for 89% (94/106) of the articles (overall  =0.83). When all 3 raters did not agree on the article conclusion category, the category assigned by the majority was used.
Other Article Characteristics
Other descriptive characteristics of the articles were classified by one of us (D.E.B.), who was blinded to article quality scores. If the classification was unclear, the principal investigator (L.A.B.) was consulted.
Peer Review Status
The peer review status was classified as either peer reviewed or non–peer reviewed based on statements in the parent publication. A publication was considered peer reviewed if it stated that it was peer reviewed, if it published a list of peer reviewers, or if it required that multiple manuscript copies be submitted for review prior to publication; otherwise, it was considered non–peer reviewed. Peer review status was classified as missing for 3 articles for which we were unable to obtain the publications' instructions for authors. These articles were automatically dropped from multivariate analyses in which the peer review status variable was included in the model.
Author Affiliation
Of the 106 articles in our study, 77% failed to disclose the sources of funding for the research. Therefore, we assessed potential financial conflicts of interest by classifying the authors of the articles as either tobacco industry affiliated or non–tobacco industry affiliated. An article was classified as having tobacco industry–affiliated authors if 1 or more of the authors had ever (1) received funding from a tobacco company or the Tobacco Institute, based on acknowledgments in articles gathered for this study and for a prior study of the literature on passive smoking18; (2) received funding from the tobacco industry–financed Council for Tobacco Research special projects division, based on a published list32; (3) received funding from the tobacco industry–financed Center for Indoor Air Research (CIAR) for a special-reviewed project, based on information gathered from CIAR for a prior study19; (4) submitted a statement on behalf of the tobacco industry regarding the EPA's risk assessment on passive smoking, based on information gathered from the EPA for a prior study33; or (5) had participated in at least 2 tobacco industry–sponsored symposia, based on information gathered for a prior study.8 Otherwise, the article was classified as having non–tobacco-affiliated authors.
Article Topic
The article topic was classified as lung cancer, heart disease, respiratory disease, multiple health outcomes, or other health effect.
Year of Publication
The year of publication was analyzed both continuously and categorically as 1980-1986, 1987-1991, or 1992-1995. These categorizations were used because the surgeon general and the National Academy of Sciences both published consensus reports on the health effects of passive smoking in 1986, and the EPA published its risk assessment of passive smoking early in 1992, and we hypothesized that the conclusions of review articles in the scientific literature might be influenced by publication of these landmark documents.
Statistical Analyses
To compare mean quality scores in various groups we used t tests and analysis of variance. Associations between categorical variables were evaluated using  2 analyses. Multiple logistic regression was used to determine which article characteristics were most highly associated with concluding that passive smoking is not harmful to health. The predictor variables were article quality score (analyzed as a continuous variable), peer review status, author affiliation, article topic, and year of publication (examined as both a continuous variable and a categorical variable). Multilevel categorical variables were modeled using indicator variables. Sensitivity analyses and diagnostic tests were performed to evaluate the multiple logistic regression model. Two-tailed P values less than .05 were considered statistically significant in all tests.
RESULTS
Descriptive characteristics of the review articles identified are presented in Table 2. Overall, 37% of articles concluded that passive smoking is not harmful. Most reviews were unsystematic but had been peer reviewed.
|
|
|
|
Table 2.—Descriptive Characteristics of Review Articles on the Health Effects of Passive Smoking
|
|
|
Thirty-one review articles (29%) were written by authors with tobacco industry affiliations. For 30 of the 31 articles, the author was affiliated with the tobacco industry either prior to or concurrent with the year of publication of the review. For the 1 review that was the exception, the article was published during the year prior to the first documented affiliation.
Table 1 presents our results related to the quality of review articles. The mean quality score was 0.36 (SD, 0.20; range, 0.04-0.94). This means that the average review article in our study satisfied only one third of the criteria on our quality assessment instrument.
Table 3 shows that there was a strong relationship between the conclusion of a review and the affiliation of its authors. Ninety-four percent (29/31) of reviews by tobacco industry–affiliated authors concluded that passive smoking is not harmful, compared with 13% (10/75) of reviews by authors without tobacco industry affiliations (P<.001). In our study, the relative risk (RR) of concluding that passive smoking is not harmful, comparing tobacco industry–affiliated authors with nonaffiliated authors, was 7.0 (95% confidence interval [CI], 3.9-12.6). The corresponding odds ratio (OR) was 94.2 (95% CI, 19.4-457.6). These measures are dissimilar because the outcome (concluding that passive smoking is not harmful) was not rare among the group of tobacco industry–affiliated authors.
|
|
|
|
Table 3.—Relationship Between Article Conclusions and Author Affiliations
|
|
|
The results of the full logistic regression model are presented in Table 4. The odds that a review article with tobacco industry–affiliated authors would conclude that passive smoking is not harmful were 88.4 times higher than the odds for a review article with non–tobacco-affiliated authors, when controlling for article quality, peer review status, article topic, and year of publication (95% CI, 16.4-476.5; P<.001).
|
|
|
|
Table 4.—Factors Associated With Concluding That Passive Smoking Is Not Harmful to Health: Multiple Logistic Regression Analysis
|
|
|
We conducted sensitivity analyses to determine whether this finding was limited to a particular subset of articles in our sample. When we limited the analysis to higher-quality articles (defined as articles receiving mean quality scores of 0.50 or higher), tobacco industry affiliation remained the only factor associated with concluding that passive smoking is not harmful (OR, 85; 95% CI, 3-2134; P=.007). (The article topic variable was dropped from this analysis because of small cell sizes that produced instability in the model.) Similarly, tobacco industry affiliation was the only factor associated with concluding that passive smoking is not harmful when the analysis was restricted to peer-reviewed articles only (OR, 93; 95% CI, 9-945; P<.001). No matter how we analyzed the data, tobacco industry affiliation was the only factor associated with concluding that passive smoking is not harmful to health in the multivariate analyses.
We also stratified the analysis by author affiliation to determine whether, within either the group of articles by tobacco industry–affiliated authors or the group of articles by non–tobacco-affiliated authors, review article conclusions might be associated with other factors. However, within each group, we found no other factors that were significantly predictive of review article conclusions.
To determine whether our results had been influenced by classification of reviews with "inconclusive" findings in the "passive smoking not harmful" category, we reanalyzed the data after excluding inconclusive reviews. This resulted in exclusion of 24 reviews (17 by tobacco-affiliated authors, 7 by nonaffiliated authors). The magnitude of the association between author affiliation and review article conclusion was stronger in this analysis (OR, 130; 95% CI, 20-862; P<.001).
Finally, we conducted diagnostic tests to determine whether some articles were highly influential in our analyses. We found that 2 articles by tobacco industry–affiliated authors that concluded passive smoking is harmful were highly influential; however, when these 2 articles were excluded from the analysis, 100% of the reviews by tobacco industry–affiliated authors concluded that passive smoking is not harmful.
COMMENT
The goal of our study was to determine whether review article quality, author affiliation, or other article characteristics were associated with concluding that passive smoking is not harmful to health. We had initially hypothesized that review articles would be more likely to conclude that passive smoking is not harmful if they were poor in quality, published in non–peer-reviewed journals or symposium proceedings, or written by authors with tobacco industry affiliations. We also speculated that the topic of a review and its year of publication might be associated with its conclusion.
We found that very few reviews had been conducted systematically, resulting in overall mean quality scores that were quite low. The low quality scores may be attributable in part to poor reporting in some of the articles; for example, several authors implied that they had conducted a review of the literature by making statements such as "there are currently x number of published studies on a particular topic." These results highlight the need for accurate reporting of study methods in reviews as well as original research articles.
The quality of a review was not associated with its conclusion when controlling for the effect of author affiliation. Using multivariate logistic regression analysis, the only factor that predicted a review article's conclusion was whether its author was affiliated with the tobacco industry. This finding was consistent and emerged no matter how we analyzed the data.
A total of 10 reviews34-43 by authors classified as non–industry affiliated concluded that passive smoking may not be harmful. In 7 cases,34-40 the authors found that the evidence was inconclusive. For example, 1 review37 stated that "[w]hile a few well-designed studies demonstrate a significant effect of passive smoking on child health, most studies had significant design problems that prevent reliance on their conclusions." Two of the other 3 reviews42-43 had authors who had some affiliation with the tobacco industry, although they did not meet the stringent criteria used to define affiliation in this study; in both cases, the authors had participated in a single tobacco industry–sponsored symposium prior to or concurrent with publication of the review. Therefore, we identified only 1 review40 written by an author without any known tobacco industry affiliations that concluded that passive smoking is not harmful to health.
Our findings suggest that the discrepancy between consensus documents and published reviews related to the health hazards of passive smoking is primarily attributable to large numbers of reviews written by authors with tobacco industry affiliations. For example, although 37% (39/106) of reviews in our study concluded that passive smoking is not harmful, 74% (29/39) of these were written by authors with tobacco industry affiliations. From the time our search ended in 1995, at least 17 reviews of the health effects of passive smoking have been published. Two of the most recent reviews by authors not affiliated with the tobacco industry conclude that passive smoking is harmful.44-45
These findings suggest that the tobacco industry may be attempting to influence scientific opinion by flooding the scientific literature with large numbers of review articles supporting its position that passive smoking is not harmful to health. This conclusion is consistent with the industry's previous strategies related to tobacco. For example, internal documents have shown that one of the tobacco industry's key strategies has been to suggest that there is doubt or controversy about scientific knowledge related to the health effects of tobacco.46-48 In this way, the industry is able to argue that government regulations are not warranted.
Our findings are unlikely to be attributable to bias. Review articles were identified using a systematic strategy and well-defined inclusion and exclusion criteria. Article quality was evaluated by independent assessors who were trained, used a slightly modified version of a valid and reliable instrument, and were blinded to study hypotheses. In addition, article conclusions were classified independently by 3 people, 2 of whom were blinded to all identifying aspects of the articles, including author names and affiliations. Furthermore, we do not feel that our findings were biased by inclusion of symposium studies that we had identified for a prior study, because our results were the same when these articles were excluded.
Our findings are consistent with previous research on both the quality and conclusions of review articles. Several studies have found that most published reviews are unsystematic and that their quality is therefore low.10-11,13, 25 In addition, other studies have found an association between the conclusions of review articles and the affiliations of their authors. For example, Assendelft et al25 found that reviews were more likely to conclude that spinal manipulation was beneficial if one of the authors was a spinal manipulator. Similarly, Chalmers et al26 showed that, for several types of controversial procedures, an author's enthusiasm for the procedure was associated with his or her specialty. Furthermore, several investigators have found that original research articles that acknowledge sponsorship from the pharmaceutical industry,20-21,23 the chemical industry,24 or the tobacco industry19 tend to draw pro-industry conclusions. Ultimately, the conclusion of any review article must be based on the judgment and interpretation of the author.
Because research studies on a variety of topics have consistently found an association between the affiliations of an author and the conclusions of his or her published research, we feel that our findings may be generalizable to review articles on topics other than passive smoking. That is, the conclusions of a review article may be suspect whenever the author has a financial interest in the outcome of the review. Therefore, our findings suggest that the authors of review articles should disclose their affiliations, sources of funding, and other potential financial conflicts of interest, and that the readers of review articles should consider these disclosures when deciding how to judge an article's conclusions.
AUTHOR INFORMATION
Dr Bero has received or currently receives research grants from the National Cancer Institute, American Cancer Society, Robert Wood Johnson Foundation, and California Tobacco-Related Disease Research Program. Both authors also receive annual royalty payments for a book they coauthored (The Cigarette Papers, published by University of California Press in 1996).
This research was sponsored by the Robert Wood Johnson Foundation (grant 024783) as part of a larger study on the content, quality, and use of tobacco industry–sponsored research.
We would like to thank Phillip Lollar for administrative assistance; the Writing Seminar at the Institute for Health Policy Studies, University of California, San Francisco, and Ira Tager, MD, MPH, for feedback on the manuscript; and our quality assessors, Peggy Lopipero, MPH, and Carolyn Klassen, MPH.
Reprints: Lisa A. Bero, PhD, Institute for Health Policy Studies, 1388 Sutter St, 11th Floor, San Francisco, CA 94109 (e-mail: bero{at}cardio.ucsf.edu).
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.
REFERENCES
| |
1. US Environmental Protection Agency. Respiratory Health Effects of Passive Smoking: Lung Cancer and Other Disorders. Washington, DC: US Environmental Protection Agency; 1992.
2. US Department of Health and Human Services. The Health Consequences of Involuntary Smoking: A Report of the Surgeon General. Rockville, Md: US Public Health Service; 1986.
3. National Academy of Sciences. Environmental Tobacco Smoke: Measuring Exposures and Assessing Health Effects. Washington, DC: National Academy Press; 1986.
4. O'Neill IK, ed, Brunnemann KD, ed, Dodet B, ed, Hoffmann D, ed. Passive Smoking: Environmental Carcinogens. Lyon, France: International Agency for Research on Cancer; 1987. IARC scientific publications, No. 81, vol 9.
5. Wells AJ. Passive smoking as a cause of heart disease. J Am Coll Cardiol. 1994;24:546-554.
ABSTRACT
6. Glantz S, Parmley W. Passive smoking and heart disease: mechanisms and risks. JAMA. 1995;273:1047-1053.
FREE FULL TEXT
7. DiFranza JR, Lew RA. Effect of maternal cigarette smoking on pregnancy complications and sudden infant death syndrome. J Fam Pract. 1995;40:385-394.
ISI
| PUBMED
8. Bero LA, Galbraith A, Rennie D. Sponsored symposia on environmental tobacco smoke. JAMA. 1994;271:612-617.
FREE FULL TEXT
9. Antman EM, Lau J, Kupelnick B, Mosteller F, Chalmers TC. A comparison of the results of meta-analyses of randomized control trials and recommendations of clinical experts. JAMA. 1992;268:240-248.
FREE FULL TEXT
10. Silagy CA. An analysis of review articles published in primary care journals. Fam Pract. 1993;10:337-341.
FREE FULL TEXT
11. Mulrow CD. The medical review article: state of the science. Ann Intern Med. 1987;106:485-488.
FREE FULL TEXT
12. Oxman AD, Guyatt GH. Guidelines for reading literature reviews. CMAJ. 1988;138:697-703.
ABSTRACT
13. Sacks HS, Berrier J, Reitman D, Ancona-Berk VA, Chalmers TC. Meta-analyses of randomized controlled trials. N Engl J Med. 1987;316:450-455.
ABSTRACT
14. Mulrow CD. Rationale for systematic reviews. BMJ. 1994;309:597-599.
FREE FULL TEXT
15. Cook DJ, Mulrow CD, Haynes RB. Systematic reviews: synthesis of best evidence for clinical decisions. Ann Intern Med. 1997;126:376-380.
FREE FULL TEXT
16. Haynes RB. Clinical review articles: should be as scientific as the articles they review. BMJ. 1992;304:330-331.
FREE FULL TEXT
17. Rochon PA, Gurwitz JH, Cheung M, Hayes JA, Chalmers TC. Evaluating the quality of articles published in journal supplements compared with the quality of those published in the parent journal. JAMA. 1994;272:108-113.
FREE FULL TEXT
18. Barnes DE, Bero LA. Scientific quality of original research articles on environmental tobacco smoke. Tob Control. 1997;6:19-26.
ABSTRACT
19. Barnes DE, Bero LA. Industry-funded research and conflict of interest: an analysis of research sponsored by the tobacco industry through the Center for Indoor Air Research. J Health Polit Policy Law. 1996;21:515-542.
ISI
| PUBMED
20. Cho MK, Bero LA. The quality of drug studies published in symposium proceedings. Ann Intern Med. 1996;124:485-489.
FREE FULL TEXT
21. Rochon PA, Gurwitz JH, Simms RW, et al. A study of manufacturer-supported trials of nonsteroidal anti-inflammatory drugs in the treatment of arthritis. Arch Intern Med. 1994;154:157-163.
FREE FULL TEXT
22. Gotzsche PC. Methodology and overt and hidden bias in reports of 196 double-blind trials of nonsteroidal antiinflammatory drugs in rheumatoid arthritis. Controlled Clin Trials. 1989;10:31-56.
FULL TEXT
|
ISI
| PUBMED
23. Davidson RA. Source of funding and outcomes of clinical trials. J Gen Intern Med. 1986;1:155-158.
ISI
| PUBMED
24. Swaen GMH, Meijers JMM. Influence of design characteristics on the outcome of retrospective cohort studies. Br J Ind Med. 1988;45:624-629.
ISI
| PUBMED
25. Assendelft WJJ, Koes BW, Knipschild PG, Bouter LM. The relationship between methodological quality and conclusions in reviews of spinal manipulation. JAMA. 1995;274:1942-1948.
FREE FULL TEXT
26. Chalmers TC, Frank CS, Reitman D. Minimizing the three stages of publication bias. JAMA. 1990;263:1392-1395.
FREE FULL TEXT
27. Mulrow CD, Oxman A. How to Conduct a Cochrane Systematic Review. San Antonio, Tex: Cochrane Collaboration; 1996.
28. Oxman AD, Guyatt GH, Singer J, et al. Agreement among reviewers of review articles. J Clin Epidemiol. 1991;44:91-98.
ISI
| PUBMED
29. Oxman AD, Guyatt GH. Validation of an index of the quality of review articles. J Clin Epidemiol. 1991;44:1271-1278.
FULL TEXT
|
ISI
| PUBMED
30. Light RJ, Pillemar DB. Summing Up: The Science of Reviewing Research. Cambridge, Mass: Harvard University Press; 1984.
31. Bland JM, Altman DG. Comparing two methods of clinical measurement: a personal history. Int J Epidemiol. 1995;24:S7-S14.
32. Glantz SA, Slade J, Bero LA, Hanauer P, Barnes DE. The Cigarette Papers. Berkeley: University of California Press; 1996.
33. Bero LA, Glantz SA. Tobacco industry response to a risk assessment of environmental tobacco smoke. Tob Control. 1993;2:103-113.
34. Tong S, McMichael AJ. Maternal smoking and neuropsychological development in childhood: a review of the evidence. Dev Med Child Neurol. 1992;34:191-197.
ISI
| PUBMED
35. Tredaniel J, Boffetta P, Little J, Saracci R, Hirsch A. Exposure to passive smoking during pregnancy and childhood, and cancer risk: the epidemiological evidence. Paediatr Perinat Epidemiol. 1994;8:233-255.
ISI
| PUBMED
36. Shimizu Y, Namekata T, Takemoto K. Epidemiological issues on involuntary smoking and lung cancer. In: Kasuga H, ed. Indoor Air Quality. New York, NY: Springer-Verlag; 1990:323-332.
37. Rubin DH, Damus K. The relationship between passive smoking and child health: methodologic criteria applied to prior studies. Yale J Biol Med. 1988;61:401-411.
ISI
| PUBMED
38. Tager IB. Health effects of involuntary smoking in the workplace. N Y State J Med. 1989;89:27-31.
ISI
| PUBMED
39. Tredaniel J, Boffetta P, Saracci R, Hirsch A. Exposure to environmental tobacco smoke and adult non-neoplastic respiratory diseases. Eur Respir J. 1994;7:173-185.
ABSTRACT
40. Saracci R. Passive smoking and lung cancer. In: Zaridze DG, Peto R, eds. Tobacco: A Major International Health Hazard. Lyon, France: International Agency for Research on Cancer; 1986:173-182.
41. Blakley BW, Blakley JE. Smoking and middle ear disease: are they related? a review article. Otolaryngol Head Neck Surg. 1995;112:441-446.
FULL TEXT
|
ISI
| PUBMED
42. Crawford WA. On the health effects of environmental tobacco smoke. Arch Environ Health. 1988;43:34-37.
ISI
| PUBMED
43. Armitage AK. Environmental tobacco smoke and coronary heart disease. J Smok Relat Disord. 1993;4:27-36.
44. Law MR, Morris JK, Wald NJ. Environmental tobacco smoke exposure and ischaemic heart disease: an evaluation of the evidence. BMJ. 1997;315:973-980.
FREE FULL TEXT
45. Hackshaw AK, Law MR, Wald NJ. The accumulated evidence on lung cancer and environmental tobacco smoke. BMJ. 1997;315:980-988.
FREE FULL TEXT
46. Bero L, Barnes D, Hanauer P, Slade J, Glantz S. Lawyer control of the tobacco industry's external research program. JAMA. 1995;274:241-247.
FREE FULL TEXT
47. Barnes D, Hanauer P, Slade J, Bero L, Glantz S. Environmental tobacco smoke. JAMA. 1995;274:248-253.
FREE FULL TEXT
48. Durbin R. The tobacco industry strategy: new subject, same tactics. Tob Control. 1993;2:8-9.
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati
What's this?
RELATED LETTERS
Industry Affiliations and Scientific Conclusions
J. Daniel Heck, Kenneth J. Gorelick, Lisa A. Bero, and Deborah Barnes
JAMA. 1998;280(13):1141-1142.
EXTRACT
| FULL TEXT
Effect of Industry Sponsorship on the Results of Biomedical Research—Reply
Justin E. Bekelman, Cary P. Gross, and Yan Li
JAMA. 2003;289(19):2503.
EXTRACT
| FULL TEXT
THIS ARTICLE HAS BEEN CITED BY OTHER ARTICLES
|
Philip Morris involvement in the development of an air quality laboratory in El Salvador
Kummerfeldt et al.
Tobacco Control 2009;18:241-244.
ABSTRACT
| FULL TEXT
Smoking and impact on health
Vineis
ERR 2008;17:182-186.
ABSTRACT
| FULL TEXT
Mobilising public opinion for the tobacco industry: the consumer tax alliance and excise taxes
Campbell and Balbach
Tobacco Control 2008;17:351-356.
ABSTRACT
| FULL TEXT
Tobacco Use Among Individuals With Schizophrenia: What Role Has the Tobacco Industry Played?
Prochaska et al.
Schizophr Bull 2008;34:555-567.
ABSTRACT
| FULL TEXT
Research ethics and lessons from Hwanggate: what can we learn from the Korean cloning fraud?
Saunders and Savulescu
J. Med. Ethics 2008;34:214-221.
ABSTRACT
| FULL TEXT
Response: The distribution and determinants of epidemiologic research
Pearce
Int J Epidemiol 2008;37:65-68.
FULL TEXT
Corporate influences on epidemiology
Pearce
Int J Epidemiol 2008;37:46-53.
ABSTRACT
| FULL TEXT
Systematic Review and Meta-analysis: When One Study Is Just not Enough
Garg et al.
CJASN 2008;3:253-260.
FULL TEXT
Financial ties and concordance between results and conclusions in meta-analyses: retrospective cohort study
Yank et al.
BMJ 2007;335:1202-1205.
ABSTRACT
| FULL TEXT
State of the Evidence on Acute Asthma Management in Children: A Critical Appraisal of Systematic Reviews
Boluyt et al.
Pediatrics 2007;120:1334-1343.
ABSTRACT
| FULL TEXT
A review of conflict of interest, competing interest, and bias for toxicologists
Claxton
Toxicol Ind Health 2007;23:557-571.
ABSTRACT
Strengthening the Reporting of Observational Studies in Epidemiology (STROBE): Explanation and Elaboration
Vandenbroucke et al.
ANN INTERN MED 2007;147:W-163-W-194.
ABSTRACT
| FULL TEXT
Old ways, new means: tobacco industry funding of academic and private sector scientists since the Master Settlement Agreement
Schick and Glantz
Tobacco Control 2007;16:157-164.
ABSTRACT
| FULL TEXT
'It's interesting how few people die from smoking': Tobacco industry efforts to minimize risk and discredit health promotion
Smith
Eur J Public Health 2007;17:162-170.
ABSTRACT
| FULL TEXT
Keeping a high standard in quantitative analyses, meta-analyses, and systematic reviews
Biondi-Zoccai et al.
Eur Heart J 2007;0:ehl502v1-1.
FULL TEXT
Evidence of publication bias in reporting acute stroke clinical trials.
Liebeskind et al.
Neurology 2006;67:973-979.
ABSTRACT
| FULL TEXT
Symposium. Relationships with Industry: Critical for New Technology or an Unnecessary Evil?
Jacobs et al.
JBJS 2006;88:1650-1663.
FULL TEXT
Conflicts of interest: how money clouds objectivity.
Smith
JRSM 2006;99:292-297.
FULL TEXT
Tobacco promotion and the initiation of tobacco use: assessing the evidence for causality.
DiFranza et al.
Pediatrics 2006;117:e1237-e1248.
ABSTRACT
| FULL TEXT
Philip Morris toxicological experiments with fresh sidestream smoke: more toxic than mainstream smoke
Schick and Glantz
Tobacco Control 2005;14:396-404.
ABSTRACT
| FULL TEXT
The most important and influential papers in tobacco control: results of an online poll
Chapman
Tobacco Control 2005;14:e1-e1.
FULL TEXT
Tobacco Money at the University of California
Glantz
Am. J. Respir. Crit. Care Med. 2005;171:1067-1069.
FULL TEXT
The limits of competing interest disclosures
Bero et al.
Tobacco Control 2005;14:118-126.
ABSTRACT
| FULL TEXT
ARTIST (Asian regional tobacco industry scientist team): Philip Morris' attempt to exert a scientific and regulatory agenda on Asia
Tong and Glantz
Tobacco Control 2004;13:ii118-ii124.
ABSTRACT
| FULL TEXT
Does the type of competing interest statement affect readers' perceptions of the credibility of research? Randomised trial
Schroter et al.
BMJ 2004;328:742-743.
FULL TEXT
Tobacco industry efforts to present ventilation as an alternative to smoke-free environments in North America
Drope et al.
Tobacco Control 2004;13:i41-47.
ABSTRACT
| FULL TEXT
Rating the strength of scientific evidence: relevance for quality improvement programs
Lohr
Int J Qual Health Care 2004;16:9-18.
ABSTRACT
| FULL TEXT
More misleading science from the tobacco industry
Thun
BMJ 2003;327:E237-238.
FULL TEXT
Acknowledgement of psychiatric research funding
HENDERSON et al.
Br. J. Psychiatry 2003;183:273-275.
FULL TEXT
Chasing the dollar: why scientists should decline tobacco industry funding
Malone and Bero
J. Epidemiol. Community Health 2003;57:546-548.
FULL TEXT
Effect of Industry Sponsorship on the Results of Biomedical Research--Reply
Bekelman et al.
JAMA 2003;289:2503-2503.
FULL TEXT
Tobacco Industry Efforts to Defeat the Occupational Safety and Health Administration Indoor Air Quality Rule
Bryan-Jones and Bero
Am. J. Public Health 2003;93:585-592.
ABSTRACT
| FULL TEXT
Review of the quality of studies on the economic effects of smoke-free policies on the hospitality industry
Scollo et al.
Tobacco Control 2003;12:13-20.
ABSTRACT
| FULL TEXT
Scope and Impact of Financial Conflicts of Interest in Biomedical Research: A Systematic Review
Bekelman et al.
JAMA 2003;289:454-465.
ABSTRACT
| FULL TEXT
Making progress with competing interests
Smith
BMJ 2002;325:1375-1376.
FULL TEXT
Does declaration of competing interests affect readers' perceptions? A randomised trial
Chaudhry et al.
BMJ 2002;325:1391-1392.
FULL TEXT
Financial Conflicts of Interest in Human Subjects Research: The Problem of Institutional Conflicts
Barnes and Florencio
J Law Med Ethics 2002;30:390-402.
Association of Journal Quality Indicators With Methodological Quality of Clinical Research Articles
Lee et al.
JAMA 2002;287:2805-2808.
ABSTRACT
| FULL TEXT
Comparison of Review Articles Published in Peer-Reviewed and Throwaway Journals
Rochon et al.
JAMA 2002;287:2853-2856.
ABSTRACT
| FULL TEXT
Attacks on Science: The Risks to Evidence-Based Policy
Rosenstock and Lee
Am. J. Public Health 2002;92:14-18.
ABSTRACT
| FULL TEXT
Constructing ""Sound Science"" and ""Good Epidemiology"": Tobacco, Lawyers, and Public Relations Firms
Ong and Glantz
Am. J. Public Health 2001;91:1749-1757.
ABSTRACT
| FULL TEXT
The Smoke You Don't See: Uncovering Tobacco Industry Scientific Strategies Aimed Against Environmental Tobacco Smoke Policies
Muggli et al.
Am. J. Public Health 2001;91:1419-1423.
ABSTRACT
| FULL TEXT
Conflict of Interest, Bias, and Objectivity in Research Articles
Starr et al.
JBJS 2001;83:1429-1431.
FULL TEXT
In Search of the Magic Nutraceutical: Problems with Current Approaches
Heyland
J. Nutr. 2001;131:2591S-2595.
ABSTRACT
| FULL TEXT
Policy makers' perspectives on tobacco control advocates' roles in regulation development
Montini and Bero
Tobacco Control 2001;10:218-224.
ABSTRACT
| FULL TEXT
Philip Morris' new scientific initiative: an analysis
HIRSCHHORN et al.
Tobacco Control 2001;10:247-252.
ABSTRACT
| FULL TEXT
The miseries of passive smoiong
Nelson
Hum Exp Toxicol 2001;20:61-83.
ABSTRACT
Editorial I: Conflicts of interest: are they a problem for anaesthesia journals? What should we do about them?
Sneyd
Br J Anaesth 2000;85:811-814.
FULL TEXT
Systematic reviews and meta-analyses on treatment of asthma: critical evaluation
Jadad et al.
BMJ 2000;320:537-540.
ABSTRACT
| FULL TEXT
Evaluation of Conflict of Interest in Economic Analyses of New Drugs Used in Oncology
Friedberg et al.
JAMA 1999;282:1453-1457.
ABSTRACT
| FULL TEXT
Evidence-based Dentistry and the Dental Research Community
Bader et al.
JDR 1999;78:1480-1483.
Print media coverage of research on passive smoking
Kennedy and Bero
Tobacco Control 1999;8:254-260.
ABSTRACT
| FULL TEXT
From in utero and childhood exposure to parental smoking to childhood cancer: a possible link and the need for action
Sasco and Vainio
Hum Exp Toxicol 1999;18:192-201.
ABSTRACT
Maternal passive smoking during pregnancy and fetal developmental toxicity. Part 1: gross morphological effects
Nelson et al.
Hum Exp Toxicol 1999;18:252-256.
ABSTRACT
Institutional addiction to tobacco
COHEN et al.
Tobacco Control 1999;8:70-74.
FULL TEXT
Editorial
Marks
J Health Psychol 1999;4:5-8.
Social Movements as Catalysts for Policy Change: The Case of Smoking and Guns
Nathanson
Journal of Health Politics, Policy and Law 1999;24:421-488.
ABSTRACT
Odds ratios should be avoided when events are common
Altman et al.
BMJ 1998;317:1318-1318.
FULL TEXT
Industry Affiliations and Scientific Conclusions
Heck et al.
JAMA 1998;280:1141-1142.
FULL TEXT
Beyond conflict of interest
Smith
BMJ 1998;317:291-292.
FULL TEXT
|
