Monday, June 25, 2007

TobaccoScam Fact Sheet Claims that Brief Exposure to Secondhand Smoke Caused 40% of Heart Attacks in Helena

The same "fact sheet" which claims that 30 minutes of secondhand smoke exposure clogs nonsmokers' arteries, gives them arteries with damage equivalent to that of a smoker, and puts them at increased risk of a heart attack or stroke also claims that brief exposure to secondhand smoke causes 40% of all heart attacks (or at least of all heart attacks in Helena, Montana).

According to the TobaccoScam fact sheet: "Breathing secondhand smoke for just twenty minutes has substantial, adverse effects on the heart, blood, and blood vessels. That's why making restaurants and bars (as well as workplaces) smokefree was associated with a 40% drop in hospital admissions for heart attacks when Helena, Montana, implemented a smokefree policy."

The Rest of the Story

What this fact sheet is claiming, then, is that brief exposure (20 minutes) to secondhand smoke causes a huge number of heart attacks. So huge, in fact, that when Helena banned smoking in bars and restaurants, the reduction in these brief exposures led to a 40% decrease in hospital admissions for heart attacks.

In other words, TobaccoScam is claiming that 40% of the heart attacks in Helena were attributable to brief exposures to secondhand smoke.

This claim seems implausible for three reasons:

First, it is scientifically unsound to conclude that the observed 40% decline in heart attack admissions in Helena over a six-month period was attributable to the smoking ban in the first place. It is highly likely that a substantial portion of this drop was due simply to random variation and that some of it was due to secular changes in heart attack admissions over time.

Second, even if the 40% decline in heart attack admissions were solely attributable to the smoking ban, it is scientifically unsound to conclude that these effects were due to reduced secondhand smoke exposure, rather than to lowered levels of active smoking (smoking cessation and reduced cigarette consumption). Certainly, it is not valid to conclude that all of the observed effect was due to reduced secondhand smoke exposure. The Helena study did not, in fact, measure the smoking status of those who suffered heart attacks, nor did it document changes in the smoking status or secondhand smoke exposure of city residents. So the study does not have the ability to determine whether any observed decline in heart attacks, even if due to the smoking ban, was due to changes in active smoking or changes in secondhand smoke exposure.

Third, it is implausible that a reduction in brief exposure to secondhand smoke could cause a 40% reduction in heart attacks. It has never been shown that brief exposure to secondhand smoke is a cause of heart attacks in the first place. Moreover, it is close to impossible that brief exposure to secondhand smoke explains 40% of all heart attacks. Smoking in its entirety is estimated to be responsible for only about 30% of heart attacks. So how could just brief exposure to secondhand smoke be responsible for 40%?

What I find most distressing about this claim is that it is unfounded. There is simply no evidence upon which to base an assertion that the 40% reduction in heart attacks in Helena was attributable solely to a reduction in secondhand smoke exposure, even if that reduction were indeed due to the smoking ban in the first place. The reduction, if due to the smoking ban, could just as easily (and probably more likely) be due to changes in active smoking. Recent evidence from New York City suggests that smoking bans can have substantial effects on active smoking rates and on cigarette consumption levels. These effects could just as easily explain any reductions in heart attacks. In fact, if I were forced to attribute any observed declines in their entirety to one factor or the other, I would choose active smoking reduction as an explanation long before I chose reduced secondhand smoke exposure resulting from the Helena smoking ban.

Readers unfamiliar with my latest commentary on the Helena-type studies may want to review it in order to understand why I do not believe any of these studies provide credible evidence that these smoking bans have resulted in drastic declines in heart attack admissions. In that post, I concluded that: "upon closer examination, the study which purports to demonstrate that a smoking ban in Bowling Green resulted in a massive decline in heart disease admissions demonstrated nothing of the sort, and possibly demonstrated that there was no significant decline in admissions attributable to the smoking ban. Like its predecessors (e.g., Helena and Pueblo), this is another example of shoddy science that apparently now passes as acceptable in tobacco control research."

Today's finding simply adds to the evidence I presented previously that the TobaccoScam fact sheet is misleading and needs to be corrected. In this case, it draws a conclusion that is not supported by any evidence and which is scientifically implausible anyway.

If public health officials in other cities that are enacting smoking bans are expecting to see immediate 40% reductions in heart attacks due to reduction in brief secondhand smoke exposures, I'm afraid they are going to be quite disappointed. There are undoubtedly health benefits to be realized from smoke-free laws; but this degree of an immediate reduction in heart attacks is probably not one of them.

As of now, the fact sheet remains unchanged. So I don't expect this particular point to be corrected, although I think it would be a great service to the public to do so. I'll report back later in the week on any changes on this site or the others I cited which are making exaggerated and deceptive claims about the acute cardiovascular effects of secondhand smoke.

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