Tuesday, February 26, 2008

Second-Hand Smoke: Scientific Documentation of its Harmfulness




1) Secondhand smoke dramatically increases the risk of heart disease and lung cancer in nonsmokers and can be controlled only by making indoor spaces smoke-free, according to a comprehensive report issued yesterday by U.S. Surgeon General Richard H. Carmona.

"The health effects of secondhand smoke exposure are more pervasive than we previously thought," Carmona said. "The scientific evidence is now indisputable: Secondhand smoke is not a mere annoyance. It is a serious health hazard that can lead to disease and premature death in children and nonsmoking adults."

According to the report, the government's most detailed statement ever on secondhand smoke, exposure to smoke at home or work increases the nonsmokers' risk of developing heart disease by 25 to 30 percent and lung cancer by 20 to 30 percent. It is especially dangerous for children living with smokers and is known to cause sudden infant death syndrome, respiratory problems, ear infections and asthma attacks in infants and children. [ source ]

2) Why Review Articles on the Health Effects of Passive Smoking Reach Different Conclusions

Deborah E. Barnes, MPH; Lisa A. Bero, PhD

JAMA (Journal of the American Medical Association). 1998;279:1566-1570.

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. . . .

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.

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.

Related article:

3) Beyond conflict of interest

Editorial: BMJ (British Medical Journal) 1998;317:291-292 ( 1 August )

Some people have taken the view that conflict of interest is a lot of fuss about nothing, or, worse, that identifying people's conflicts of interest is a form of McCarthyism. Those who argue against concerns about conflict of interest say that science is science, methods are transparent, data either support the conclusions or do not, and it is neither here nor there whether researchers have, for example, shares in a company that manufactures a drug included in a trial.

This argument is becoming steadily less tenable as evidence accumulates on the influence of conflict of interest. Several studies have shown that financial benefit will make doctors more likely to refer patients for tests, operations, or hospital admission, or to ask that drugs be stocked by a hospital pharmacy. Now we are beginning to have data on the effects of
conflict of interest on publications. Original papers published in journal supplements sponsored by pharmaceutical companies are inferior to those published in the parent journal. Reviews that acknowledge sponsorship by the pharmaceutical or tobacco industry are more likely to draw conclusions that are favourable to the industry.

. . . The second study, published in JAMA, looked at what characteristics determined the conclusions of review articles on passive smoking. The authors identified 106 reviews, with 37% concluding that passive smoking was not harmful and the rest that it was. A multiple regression analysis controlling for article quality, peer review status, article topic, and year of
publication found that the only factor associated with the review's conclusion was whether the author was affiliated with the tobacco industry. Three quarters of the articles concluding that passive smoking was not harmful were written by tobacco industry affiliates. The study authors 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." Again, only a minority of the articles (23%) disclosed the sources of funding for research. The authors had to use their own database of researchers linked with the tobacco industry to determine whether authors had such links.

These two papers and their predecessors begin to build a solid case that conflict of interest has an impact on the conclusions reached by papers in medical journals. They also show convincingly that medical journals are failing to get authors to declare conflicts of interest.

4) Constructing "Sound Science" and "Good Epidemiology": Tobacco, Lawyers, and Public Relations Firms

Elisa K. Ong, MD, MS and Stanton A. Glantz, PhD

November 2001, Vol 91, No. 11 | American Journal of Public Health 1749-1757

ABSTRACT

The tobacco industry has attacked "junk science" to discredit the evidence that secondhand smoke—among other environmental toxins—causes disease. Philip Morris used public relations firms and lawyers to develop a "sound science" program in the United States and Europe that involved recruiting other industries and issues to obscure the tobacco industry's role. The European "sound science" plans included a version of "good epidemiological practices" that would make it impossible to conclude that secondhand smoke—and thus other environmental toxins—caused diseases.

Public health professionals need to be aware that the "sound science" movement is not an indigenous effort from within the profession to improve the quality of scientific discourse, but reflects sophisticated public relations campaigns controlled by industry executives and lawyers whose aim is to manipulate the standards of scientific proof to serve the corporate interests of their clients.

5) The miseries of passive smoking

Ed Nelson

Toxicology Laboratory, Institute of Hygiene and Occupational Medicine, University Medical Center, D-45147 Essen, Germany

Human & Experimental Toxicology, Vol. 20, No. 2, 61-83 (2001)

Passive smoking is defined as an involuntary exposure to a combined but diluted cigarette sidestream smoke (SS, gas and particle phases that are evolved fromthe smoldering end ofacigarettewhilethesmokerisnotpuffing) andthe exhaled smoke from smokers. SS contains numerous cytotoxic substances such as polycyclic aromatic hydrocarbons (PAHs), aromatic
amines, nitrosamines, heavy metals, poisonous gases, pesticide residues, and radioactive elements in quantities much higher than those found from the cigarette mainstream smoke (MS) which is puffed by smokers. Passive smoking is found to be the cause of death from cancers and cardiac disease. Furthermore, it damagingly involves reproductive organs, the nervous system, genetic materials, and is particularly hazardous to mother and child during pregnancy and to those with a history of asthma, chronic infections, induced or earned immune deficiency, or predisposed susceptibility.

6) Prenatal and Postnatal Environmental Tobacco Smoke Exposure and Children’s Health

Joseph R. DiFranza, MD*, C. Andrew Aligne, MD, MPH{ddagger} and Michael Weitzman, MD{ddagger},§

Pediatrics Vol. 113 No. 4 April 2004, pp. 1007-1015

Children’s exposure to tobacco constituents during fetal development and via environmental tobacco smoke (ETS) exposure is perhaps the most ubiquitous and hazardous of children’s environmental exposures. A large literature links both prenatal maternal smoking and children’s ETS exposure to decreased lung growth and increased rates of respiratory tract infections, otitis media, and childhood asthma, with the severity of these problems increasing with increased exposure. Sudden infant death syndrome, behavioral problems, neurocognitive decrements, and increased rates of adolescent smoking also are associated with such exposures. Studies of each of these problems suggest independent effects of both pre- and postnatal exposure for each, with the respiratory risk associated with parental smoking seeming to be greatest during fetal development and the first several years of life.

7) The Smoke You Don't See: Uncovering Tobacco Industry Scientific Strategies Aimed Against Environmental Tobacco Smoke Policies

Monique E. Muggli, MPH, Jean L. Forster, PhD, MPH, Richard D. Hurt, MD and James L. Repace, MSc

September 2001, Vol 91, No. 9 | American Journal of Public Health 1419-1423

Objectives. This review details the tobacco industry's scientific campaign aimed against policies addressing environmental tobacco smoke (ETS) and efforts to undermine US regulatory agencies from approximately 1988 to 1993.

Methods. The public availability of more than 40 million internal, once-secret tobacco company documents allowed an unedited and historical look at tobacco industry strategies.

Results. The analysis showed that the tobacco industry went to great lengths to battle the ETS issue worldwide by camouflaging its involvement and creating an impression of legitimate, unbiased scientific research.

Conclusions. There is a need for further international monitoring of industry-produced science and for significant improvements in tobacco document accessibility.

8) Cardiovascular Effects of Secondhand Smoke Nearly as Large as Smoking

Joaquin Barnoya, MD, MPH; Stanton A. Glantz, PhD

Circulation. 2005;111:2684-2698.

Background— Secondhand smoke increases the risk of coronary heart disease by {approx}30%. This effect is larger than one would expect on the basis of the risks associated with active smoking and the relative doses of tobacco smoke delivered to smokers and nonsmokers.

Methods and Results— We conducted a literature review of the research describing the mechanistic effects of secondhand smoke on the cardiovascular system, emphasizing research published since 1995, and compared the effects of secondhand smoke with the effects of active smoking. Evidence is rapidly accumulating that the cardiovascular system—platelet and endothelial function, arterial stiffness, atherosclerosis, oxidative stress, inflammation, heart rate variability, energy metabolism, and increased infarct size—is exquisitely sensitive to the toxins in secondhand smoke. The effects of even brief (minutes to hours) passive smoking are often nearly as large (averaging 80% to 90%) as chronic active smoking.

Conclusions— The effects of secondhand smoke are substantial and rapid, explaining the relatively large risks that have been reported in epidemiological studies.

9) Tobacco Industry Efforts Undermining Evidence Linking Secondhand Smoke With Cardiovascular Disease

Elisa K. Tong, MD, MA; Stanton A. Glantz, PhD

Circulation. 2007;116:1845-1854.

Background— The scientific consensus that secondhand smoke (SHS) increases cardiovascular disease (CVD) risk by 30% is based on epidemiological and biological evidence. The tobacco industry has contested this evidence that SHS causes CVD, but how and why they have done it has not been described.

Conclusions— The tobacco industry attempted to undermine the evidence that SHS causes CVD to fight smoke-free regulations while developing approaches to support new products that claim to reduce harm. The industry interest in preserving corporate viability has affected the design and interpretation of their cardiovascular studies, indicating the need for great caution in current debates about future tobacco industry regulation and development of reduced-harm tobacco products.

10) Mortality and morbidity from coronary heart disease attributable to passive smoking

Jan Heidrich, J├╝rgen Wellmann, Peter U. Heuschmann, Klaus Kraywinkel and Ulrich Keil

European Heart Journal 2007 28(20):2498-2502; doi:10.1093/eurheartj/ehm151

Aims: Passive smoking is associated with increased risk of coronary heart disease (CHD). This study estimates CHD mortality and morbidity attributable to passive smoking in Germany and demonstrates variations in the number of estimated deaths depending on underlying assumptions.

Conclusion: The estimated burden of passive smoking heavily depends on the definition of underlying parameters. Using an evidence-based approach reveals a substantial burden of passive smoking in terms of CHD mortality and morbidity reflected by six CHD deaths and 10 incident CHD cases every day in Germany.

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