Second-Hand Smoke's Associated With Increased Risk Of Heart Disease
- The March 25, 1999 issue of the New England Journal of Medicine contained a
fine article by He, et al (Passive smoking and the risk of coronary heart
disease: A Meta analysis of epidemiologic studies, NEJM 1999; 340:920-926)
which convincingly shows that there passive smoking increases the risk of
heart disease by 20-30%.
The paper, which has 53 references, carefully
considers the usual issues of misclassification error, publication bias,
and confounding. It carefully and systematically excludes these potential
problems and convincingly demonstrates an increase in risk.
It also carefully addresses the fact that the risk of heart disease due to
secondhand smoke exposure is large for the dose when compared with the
effects of active smoking. Most experts now think that this fact is due to
a nonlinear dose-response curve, with the cardiovascular system very
sensitive to small doses of toxins in the secondhand smoke.
comes from studies of platelet and endothelial function in both animal and
human studies. There is also a recent epidemiological analysis of this
issue (Law M, Morris J, Wald N. Environmental tobacco smoke exposure and
ischaemic heart disease: An evaluation of the evidence Br. Med. J.
1997;315:973-980) that supports this view.
Given this strong case, I was surprised to find a commentary in the same
issue of NEJM by John Bailar, which concluded that "we still do not know,
with accuracy, how much or even whether, exposure to environmental tobacco
smoke increases the risk of coronary heart disease." In writing this
commentary, Bailer only cited three papers, He's paper, a comparison of
meta-analysis with randomized controlled trials, and a commentary he wrote
on issues in meta-analysis. He paid no mind to the literature in cardiology.
Bailar dismisses the evidence from experimental and clinical studies which
form the backbone of modern cardiology, saying that only epidemiology can
answer questions. He says: "Responses in animals may not be like those in
humans, laboratory studies involving human subjects must necessarily be of
short duration, and reports of clinical series are subject to a range of
In fact, it is just these kind of studies that have solidified the
case linking secondhand smoke with heart disease, since it is possible to
show rapid and large (compared to the dose) effects on key cardiac and,
more important, vascular functions. Rather than engage this literature,
Bailer simply dismisses it out of hand.
He also criticises He et al for asserting that they have avoided the issue
of publication bias when they failed to detect such bias in a "funnel plot"
which people think (including lots of tobacco industry consultants) detect
such bias. Bailer says that even though there is no evidence for
publication bias, it might still be there.
Bailar even criticises He et al for pointing out that the results of all
the studies of secondhand smoke and heart disease are reasonably
consistent. I was trained that consistent results are a good thing.
Bailer also says he does not believe the results because they are "too
big." Unlike Law et al, who systematically looked at the evidence and
ended up concluding that the effects of secondhand smoke were consistent
with active smoking, Law just offers a personal opinion, with no evidence.
He then essentially says that the only epidemiology that is useful is a
randomized controlled trial. Unfortunately, one cannot do a randomized
controlled trial on the effects of secondhand smoke on heart disease. I do
not think it would be possible to study ANY environmental toxin in a way
that Bailar would find convincing.
I must say that I was amazed at the low quality of this editorial. When an
editor invites a commentary on a paper like this, it is customary for the
author to present a "mini-review" that cites relevant papers to bolster
what ever point he or she is making. Bailar just makes flat statements
without citing any evidence to support these statements.
I was also surprised that NEJM chose him to write such a commentary.
Normally one solicits editorials from knowledgeable experts. While Bailar
was written on meta-analysis in general (he doesn't like it), he has no
experience or knowledge of the special issues related to heart disease.
Here are his recent publications:
- Forrester JE, Bailar JC, 3rd, Esrey SA, Josˇ MV, Castillejos BT, Ocampo
G. Randomised trial of albendazole and pyrantel in symptomless trichuriasis
in children [see comments] Lancet. 1998;352:1103-8.
- Bailar JC, 3rd. Diagnostic drift in the reporting of cancer incidence
[letter; comment] Journal of the National Cancer Institute. 1998;90:863-4.
- Wegman DH, Woods NF, Bailar JC. Invited commentary: how would we know a
Gulf War syndrome if we saw one? [comment] American Journal of
Epidemiology. 1997;146:704-11; discussion 712.
- Bailar JC, 3rd. The promise and problems of meta-analysis [editorial;
comment] [see comments] New England Journal of Medicine. 1997;337:559-61.
- Bailar JC, 3rd, Gornik HL. Trends in cancer mortality: perspectives from
Italy and the United States Medicina del Lavoro. 1997;88:274-86.
- Bailar JC, 3rd, Gornik HL. Cancer undefeated [see comments] New England
Journal of Medicine. 1997;336:1569-74.
- Bailar JC, 3rd, MacMahon B. Randomization in the Canadian National
Breast Screening Study: a review for evidence of subversion [see comments]
- Bailar JC, 3rd. Surgery for early breast cancer--can less be more?
[editorial; comment] [see comments] New England Journal of Medicine.
- Bailar JC, 3rd. The Devi case and more [letter; comment] Science.
- Macarthur C, Foran PJ, Bailar JC, 3rd. Qualitative assessment of
studies included in a meta-analysis: DES and the risk of pregnancy loss
Journal of Clinical Epidemiology. 1995;48:739-47.
- Bailar JC, 3rd. Monitoring human tissues for toxic substances: a
follow-up to the National Academy of Sciences (NAS) report Environmental
Health Perspectives. 1995;103 Suppl 3:81-4.
- Bailar JC, 3rd. The practice of meta-analysis Journal of Clinical
Given the large body of evidence available to demonstrate not only that
secondhand smoke causes heart disease, but also HOW, one would have
expected that NEJM would have solicited an expert with some experience in
the relevant areas of cardiovascular science to comment on the He et al paper.
I am sure that we will be hearing a lot about Bailar's commentary from the
tobacco industry. In considering how to react, one should consider the source.
- Stan Glantz, email@example.com
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