The Who Study
The World Health Organization's first study on SHS is a textbook example
right way to conduct an epidemiological study. Unfortunately
for them, it yielded unexpected results. They responded by doing a
second one, a meta-analysis, that allowed them to extract the results
they wanted. This is an analysis of their first study.
Fact: The World Health Organization
conducted a study of Environmental Tobacco Smoke (ETS) and lung cancer
Fact: ETS is commonly referred
to as Second Hand Smoke (SHS). The two terms are interchangeable.
Fact: This was a case control
study using a large sample size.
Fact: The purpose of the study
was to provide a more precise estimate of risk, to discover any differences
between different sources of ETS, and the effect of ETS exposure on
different types of lung cancer.
Fact: The study was conducted
from twelve centers in seven European countries over a period of seven
Fact: The participants consisted
of 650 patients with lung cancer and 1542 control subjects. Patients
with smoking related diseases were excluded from the control group.
None of the subjects in either group had smoked more than 400 cigarettes
in their lifetime.
Fact: Three of the study centers
interviewed family members of the participants to confirm the subjects
were not smokers.
Fact: The study found no statistically
significant risk existed for non-smokers who either lived or worked
Fact: The only statistically
significant number was a decrease in the risk of lung cancer
among the children of smokers.
Fact: The study found a Relative
Risk (RR) for spousal exposure of 1.16, with a Confidence Interval (CI)
of .93 - 1.44. In layman's terms, that means
Exposure to the ETS from a spouse increases
the risk of getting lung cancer by 16%.
Where you'd normally find 100 cases of lung
cancer, you'd find 116.
Because the Confidence Interval includes 1.0, The Relative Risk of 1.16 number is not statistically significant.
Fact: The real RR can be any
number within the CI. The CI includes 1.0, meaning that the real
number could be no increase at all. It also includes numbers below
1.0, which would indicate a protective effect. This means that the
RR of 1.16 is not statistically significant.
Fact: A RR of less than 2.0
is usually not considered important and, most likely to be due to
error or bias. An RR of 3.0 or higher is considered desirable. (See Statistics 101 for
This rule of thumb is routinely ignored by the anti-smoker activists.
Fact: The study found no Dose/Response
relationship for spousal ETS exposure. See Statistics
102 for more information.
Fact: The RR for workplace ETS
was 1.17 with a CI of .94 - 1.45, well below the preferred 2.0 - 3.0,
and with another CI that straddled 1.0.
Fact: The RR for exposure from
both a smoking spouse and a smoky workplace was 1.14, with a CI of .88
Fact: The RR for exposure during
childhood was 0.78, with a CI of .64 - .96. This indicates a protective
effect! Children exposed to ETS in the home during childhood are 22%
less likely to get lung cancer, according to this study. Note
that this was the only result in the study that did not include 1.0
in the CI.
The WHO quickly buried the report. The British press got wind of it
and hounded them for weeks.
Fact: On March 8, 1998, the
British newspaper The Telegraph reported "The world's leading health
organization has withheld from publication a study which shows that
not only might there be no link between passive smoking and lung cancer
but that it could have even a protective effect."
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Finally, the WHO issued a press release. Although their study showed
no statistically significant risk from ETS, their press release had
the misleading headline "Passive Smoking Does Cause Lung Cancer - Do
Not Let Them Fool You." (I say "misleading" because it would
be impolite to call it an outright lie.)
Fact: In paragraph four
they admitted the facts: "The study found that there was an estimated
16% increased risk of lung cancer among nonsmoking spouses of smokers.
For workplace exposure the estimated increase in risk was 17%. However,
due to small sample size, neither increased risk was statistically
significant." (Emphasis added.)
Fact: The press release
doesn't mention the one statistically significant result from the study,
that children raised by smokers were 22% less likely to get lung cancer.
Fact: The WHO tried to blame
the results on a small sample size. However, in the Journal of the
National Cancer Institute, where the results were published, the researchers
clearly state: "An important aspect of our study in relation to previous
studies is its size, which allowed us to obtain risk estimates with
good statistical precision..."
It should also be noted that the most likely effect of a larger sample size wouldn't be a large change to the RR, but a narrowed CI.
An abstract of the study is available here.
The entire study can be found here.
The WHO's press release is located here.
has lots of links to articles and editorials on this subject.