Smoking does not cause cancer.
[Update 10-Deember-2007 @ 17:38, since this post went up 3 days ago, I have had a few search engine hits using the keyword smoking on this post. To dispel any possible confusion: the title is ironic. Smoking increases the risk and incidence of cancer. So do oral contraceptives. However, both also have positive side effects. Smoking appears to reduce the incidence of Alzheimer's. Researchers are currently looking into a nicotine like compound found in a marine creature as a possible treatment for Alzheimer's (why they don't look at tobacco, I don't know - probably because it would not be politically correct). Oral contraceptives reduce the incidence of certain rare forms of cancer, however, the sum of cancers prevented and cancers caused show an overall increase in the number of cancer cases.]
I am still in an anti-spinning mood.
Eleven years ago or so, the Ottawa Citizen ran a front page article on the pill. The headline (in the biggest font I ever recall seeing) was something like “PILL DOES NOT CAUSE CANCER”.
The lead-in paragraph went something like:
After more than 30 years, women all over world can breath a collective sigh of relief as an extensive study proves that the pill does not cause cancer.
Of course, buried deeper in the article was a short throw away paragraph stating that women on the pill do experience increased incidence of cancer, but 10 years after stopping use the rate drops similar levels as women who have never used the pill.
I think the report all this was based on is "Evidence-guided prescribing of combined oral contraceptives: Consensus statement" from the September 1996 issue of the journal Contraceptive. However, I have never read it, although, I was tempted yesterday to pay $30 to get a copy (after subscribing to the site), but I still prefer to read it for free - so, if anyone has a copy they would like to send me, I would be much obliged. Anyway ...
I immediately made the connection with smoking because research shows that 10 years after you quit your risk of cancer drops to levels similar to that of a non-smoker. Whenever I mention this to people they immediately respond that I am confusing two separate things and should leave the heavy thinking to the experts (ok, maybe I infer that last part).
So, I abstract it for them: "If I tell you that consumption of substance S results in an increased incidence of cancer. Is substance S a carcinogen?"
The answer back is always, "Yes, but I still think you are confusing things."
For the extra curious:
Oral contraceptives increase the risk of breast (1.3x), cervical (1.5x - 2.5x) and liver cancer. It is always referred to as "slight increase". They reduce the risk of ovarian (0.4x - 0.8x) and endometrial (0.5x) cancer. It is always referred to as "significant decrease".
Lung cancer rates among non-smokers is 0.5%. Heavy smoking increases the risk 20-fold to 10% (or spun the other way, heavy smokers have a 90% chance of NOT developing lung cancer).
Demographic studies show that people over the age of 90 have a 1 in 9 chance of developing lung cancer. The moral? Living to extreme old age is a greater risk factor for lung cancer than smoking.
I love information, it can be presented in so many interesting ways and still be accurate.