The World Health Organization's Second Hand Smoke

[N2Advnture]

The World Health Organization's Second Hand Smoke Study

The World Health Organization's first study on second hand smoke is a textbook example of the 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 in Europe.

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 years.

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 with smokers.

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.
-But-

• 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.

This rule of thumb is routinely ignored by the anti-smoker activists.

Fact: The study found no Dose/Response relationship for spousal ETS exposure.

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 - 1.47.

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."

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:
http://www.ncbi.nlm.nih.gov/entrez/q...&dopt=Abstract

The entire study can be found here:
http://www.obscurious.co.uk/componants/smoking1440.pdf
(.pdf file)

The WHO's press release is located here:
http://www.who.int/inf-pr-1998/en/pr98-29.html

<b>Synopsis of the WHO Study provided courtesy of The Hitt Chronicle, here/b>
http://www.davehitt.com

I hope this helps and happy smoking!

~Mark

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[weak_link]

Great post, thanks Mark. S

Something tells me we won't be seeing this in the New York Times either.

[VirtualSmitty]

Good read, thanks Mark.