Friday, May 16, 2003 :::
New York Mayor Michael Bloomberg
says
his ban on smoking in bars and restaurants,
which took effect last month, will save "literally tens of thousands of lives." Anti-tobacco activist
Stanton Glantz
claims
such bans cut heart attack rates in half.
In a political environment where such extravagant claims are credulously accepted, it's
useful to be reminded that the scientific debate about the hazards of secondhand smoke is far
from settled. A
study
in the May 17 issue of the British Medical Journal shows once
again how tricky it is to measure the effects of environmental tobacco smoke (ETS).
UCLA epidemiologist James Enstrom and State University of New York epidemiologist
Geoffrey Kabat analyzed data from an American Cancer Society study that tracked 118,000
Californians from 1959 until 1998. They focused on 35,561 subjects who had never smoked and
whose spouses' smoking habits were determined through a questionnaire. As is typical of
research in this area, Enstrom and Kabat used marriage to a smoker as an indicator of ETS
exposure, subdividing subjects based on how much their spouses smoked.
"No significant associations were found for current or former exposure to environmental
tobacco smoke," they report. "The results do not support a causal relation between environmental
tobacco smoke and tobacco related mortality, although they do not rule out a small effect....Given
the limitations of the underlying data in this and other studies of environmental tobacco smoke
and the small size of the risk, it seems premature to conclude that environmental tobacco smoke
causes death from coronary heart disease and lung cancer."
Since anti-smoking activists and public health officials confidently assert annual death
tolls from secondhand smoke of 50,000 or more, you may suspect that Enstrom and Kabat's
findings are unusual. They are in fact similar to the results of most studies looking for a
connection between ETS and lung cancer or heart disease. Such research typically finds small,
statistically insignificant associations.
If you pool the data together, you can generate statistically significant results. But such
meta-analyses tend to mask the weaknesses of the studies on which they're based.
As Enstrom and Kabat note, these weaknesses include the possible misclassification of
current or former smokers as lifelong nonsmokers. Because smokers tend to marry smokers and
are at an elevated risk of lung cancer and heart disease regardless of their ETS exposure, that
kind of mistake could account for the observed associations.
Spouses also tend to share other habits—related to diet and exercise, for example—that can
contribute to illness. Since smokers tend to be less health-conscious and risk-averse than
nonsmokers, their spouses might be more prone to disease even if ETS had no effect. Another
interesting point raised by Enstrom and Kabat is the effect of being widowed, which happens
more often to spouses of smokers and is independently associated with higher death rates.
Finally, there is the problem of publication bias: Studies that find an association are more
likely to see print. Hence the link between ETS exposure and fatal disease could be even weaker
than it looks in the published research.
The question is not whether tobacco smoke can be dangerous. At high enough levels, it
clearly is, as Enstrom and Kabat's study confirms. "As expected," they write, "there was a
strong, positive dose-response relation between active cigarette smoking and deaths from
coronary heart disease, lung cancer, and chronic obstructive pulmonary disease."
The question is whether there's a threshold below which tobacco smoke has no
measurable impact on mortality. Based on the epidemiological data, Enstrom and Kabat calculate
that smoking one cigarette a day would be associated with something like a 20 percent increase
in lung cancer risk (as opposed to an increase of roughly 1,000 percent for a pack a day) and
virtually no increase in heart disease risk.
"It is generally considered that exposure to environmental tobacco smoke is roughly
equivalent to smoking one cigarette per day," Enstrom and Kabat note. If so, a small increase in
lung cancer risk is possible, but the commonly reported 30 percent increase in heart disease risk—the purported cause of almost all the deaths attributed to secondhand smoke—is highly
implausible.
Tobaccophobes such as Michael Bloomberg and Stanton Glantz are determined to
eliminate smoking from bars and restaurants regardless of what the evidence shows. But those of
us who have more respect for the truth should not let them banish skepticism along with cigarette
smoke.
::: posted by Creditwrench at 10:45 AM
Monday, May 12, 2003 :::
This is the new blog home of The Oklahoma Smoker's Rights Group of Oklahoma City.
President Aubrey King
Vice Pres Bill Bauer
Secy-Treas. Kathy King.
::: posted by Creditwrench at 9:41 PM
