FAQ: The WHO study, the UCLA study, and owning a bird causes Lung Cancer
The WHO study was published in the Journal of the National Cancer Institute. Upon examination of 650 patients with lung cancer who had not smoked more than 400 cigarettes during their lifetime, it was found they had a 1.16-fold increased likelihood of contracting lung cancer versus 1542 control subjects. Is this significant? View it for yourself.
There was no clear dose-response relationship and it was found those exposed during childhood had 0.78 the risk of those who were not among those who never smoked.
One problem here is the confidence limits. As the authors state, the possibility exists that the actual result could be as low as 0.94 risk among those 650 patient nonsmokers with lung cancer. On the other hand, the risk could actually be between 0.64 and 0.96 among those with childhood exposure. WHO claims the 1.16 risk was statistically significant. There are a few problems with that claim. First, epidemiologists generally recognize any found risk less than 2.00 is unreliable.
Second, when results below the 2.00 threshold are found, the reliability decreases with the number of study subjects. 650 patients is a low number. Third, this kind of study done by WHO was what is called a case-controlled study. In a case controlled study, researchers interview patients with the disease being studied, and essentially ask them how they got the disease.
The patients are asked to recall their lifetime exposure to risks listed by the researchers. In the case of the WHO study, this means that for every 116 nonsmoking lung cancer patients who recalled being exposed to excessive secondhand smoke, there were 100 who did not. These patients would not be expected to know if they lived in a house with a radon problem, at some point in time, or used some product made of asbestos, etc. Of course, by 1998, when the WHO study had been published, almost everyone had heard of the claimed secondhand smoke risk. So you have a situation here where 116 out of every 216 patients who are as mad as hell because they are going to die from lung cancer, and never smoked, blamed their lung cancer on past secondhand smoke exposure. This is why many claim the WHO study is statistically insignificant, while WHO claims it is.
What I am further concerned about is what I call the insurance situation.... Since about 1980, health insurance companies have given premium discounts to nonsmokers. If 16 out of every 216 nonsmoking patients with lung cancer in the WHO study were actually smokers, but lied on their health insurance applications to save premiums, then we have explained even the admittedly weak evidence WHO used to conclude secondhand smoke exposure can cause 1.16 times as much lung cancer in nonsmokers. And would someone who was actually a smoker, but lied on their insurance, admit to it after being diagnosed with lung cancer? AN EMPHATIC NO !!!!! That would cause continuing coverage for treatment to be denied...
A much better way to assess if secondhand smoke causes lung cancer, or heart disease for that matter, is to conduct what is called a cohort study, as opposed to a case controlled study. The reason for this is because in a cohort study, everyone is healthy when the study is begun. It is less likely the researchers and later victims of the disease being studied are biased. Recently such a study has been published. Enstrom and Kabat found absolutely no risk at all from secondhand smoke. Not even a statistically insignificant risk.
READ.
When compared to the WHO study, there are two major differences between them. First, the statistically weak and uncertain WHO study had only 650 participants, the statistically reliable Enstrom study had 35,000 participants. Second, the statistically weak and uncertain WHO study was a case-controlled study, the statistically reliable Enstrom study was a cohort study.
And I see this time-and-time again. For example, in the 1992 EPA report specifically states that out of the 58 studies they could have combined to assess if secondhand smoke causes lung cancer, they actually combined only 13 and all but one was a case-controlled study, with relatively few participants. The EPA report was the equivalent of concluding all the fruit on a cherry tree is fresh, by picking only the fresh fruit off the cherry tree and only studying the picked fruit to ascertain freshness....That's why they call it cherry-picking...
Guilt by Association? Some Cancer Epidemiology favorites by Nancy Volkers
Owning a pet bird may increase your risk of Lung cancer
http://jncicancerspectrum.oxfordjournals.org/cgi/content/full/jnci;94/24/1826