A leading national advocacy group which promotes smoke-free policies and educates the public about the health effects of secondhand smoke is claiming that there are virtually no differences in health effects between active and passive smoking. Americans for Nonsmokers' Rights (ANR) makes the claim on its online fact sheet entitled: "Secondhand Smoke: The Science."
Specifically, ANR claims that: "there are virtually no health disparities between active and passive smoking."
ANR further claims that: "The risks of heart disease associated with secondhand smoke are twice what were previously thought and are virtually indistinguishable from those associated with active smoking."
ANR supports both claims by citing a single article (see: Whincup PH, et al. Passive smoking and risk of coronary heart disease and stroke: prospective study with cotinine measurement. BMJ 2004; 329:200-205).
The Rest of the Story
ANR's claim that there are virtually no health disparities between active and passive smoking is unfortunately (or fortunately, depending on how you look at it) a lie.
I say fortunately because if ANR were being truthful in claiming that passive smoking has virtually the same level of health effects as active smoking, then there would be tens of thousands more deaths from secondhand smoke than we currently observe.
I honestly don't understand how ANR can claim that there are virtually no health disparities between active and passive smoking. That implies that active smoking is virtually no more dangerous than exposure to secondhand smoke. We know this is not true, because there is a dose-response relationship between tobacco smoke exposure and lung cancer. The relative risk of lung cancer among active smokers is about 17, while the relative risk of lung cancer among passive smokers is about 1.3. How ANR can claim that 17 is "virtually" the same as 1.3 is beyond my understanding of basic mathematics.
Even if we restrict ourselves to the risk of heart disease, the scientific evidence simply doesn't support the conclusion that the risk of heart disease is "virtually" the same for active and passive smokers.
ANR acknowledges that the relative risk for heart disease associated with passive smoking is about 1.5 or 1.6. A very large and perhaps the most recent study of the relative risk of heart disease among active smokers (the Nurses Health Study) revealed a relative risk of 3.12 for women smoking 1-14 cigarettes per day and 5.48 for women smoking 15 or more cigarettes per day. The CDC estimates that the overall relative risk for heart disease mortality associated with secondhand smoke exposure is about 2.0 (this is going to be lower than the relative risk associated with the incidence of heart disease). There are a few studies which suggest that the long-term relative risk for heart disease may be on the order of about 1.3 for light active smokers of just 1-9 cigarettes per day (this is what Whincup et al. found). Thus, even if we restrict ourselves to the risk for heart disease, it is not accurate to state that the effects of secondhand smoke and active smoking are virtually the same. There appears to be a clear dose-response relationship (albeit a non-linear one, unlike for lung cancer), and for active smokers of a half pack per day or more, the risk of heart disease is undeniably substantially higher than for passive smokers.
The Whincup study itself does not support ANR's contention that there are virtually no health disparities between active and passive smoking. The article makes no such claim.
Moreover, the Whincup article does not even claim that there are no health disparities between active and passive smoking with regards to heart disease. While the article does find that for very light active smokers (less than half pack per day), the short-term relative risks for heart disease are similar to those among passive smokers, it is very misleading to represent this finding as establishing that there are no health disparities in the risk of heart disease between active and passive smokers. First, the risk of heart disease among the majority of active smokers (who smoke half pack per day or more) is substantially higher than among passive smokers. Second, if you examine Table 3 in the Whincup paper, you'll see that even among light active smokers, upon long-term follow-up there is a clear divergence in the heart disease risk compared to passive smokers.
If ANR were to inform an active smoker that his risk of heart disease was no different than that of a passive smoker, it would essentially represent malpractice, because unless this smoker is an extremely light smoker, the information is undeniably false. Such advice could encourage a smoker to continue smoking rather than to quit, because it minimizes the true health effects of active smoking.
It is also interesting to note that while ANR is apparently so impressed by the importance of the Whincup study, it fails to inform the public that the very same study found no significant increase in stroke risk among passive smokers. Yet ANR claims in its fact sheet that: "There is a link between secondhand smoke to an increased risk of stroke." Here, ANR cites a different study.
It appears that ANR is just cherry-picking the studies it wants to in order to support the claims that it wants to make. If the Whincup study is so reliable that it can be counted on in making the claim that passive smoking causes heart disease, then why is the very same study unreliable when it finds that passive smoking in the very same subjects did not increase their risk of stroke?
By the way, I am not arguing here that secondhand smoke is not related to stroke risk. I believe that if one looks at the overall evidence, there does appear to be a causal link. However, I am just pointing out that ANR's approach of simply citing a specific study here or there to support its claims is tantamount to cherry-picking, especially when they ignore findings from the very studies they are citing.
The rest of the story is that ANR's "fact sheet" which is purportedly bringing us "The Science" on secondhand smoke is actually telling us a lie when it claims that "there are virtually no health disparities between active and passive smoking." There are, in fact, very important dose-related health disparities, and it is critical that the public appreciate the dose-response nature of the relationship between tobacco smoke exposure and adverse health effects.
I do not believe it is necessary for ANR to lie like this in order to impress upon the public the damaging health effects associated with secondhand smoke. I think the truth is certainly enough.