Did New York's Smoking Ban Cut Heart Attacks?


In his latest attempt to make the claim that smoking bans cause an immediate 40 percent drop in heart attacks seem less preposterous, Stanton Glantz is citing data from New York City, where a ban on smoking in bars and restaurants took effect in 2003. Glantz claims there was "a 13% drop in heart attacks in New York City" between 2003 and 2004, which "provides more evidence for a large immediate effect of eliminating exposure to SHS [secondhand smoke]." Michael Siegel, who supports smoking bans but has been challenging his fellow anti-smoking activists to stop abusing science in service of their cause, notes several problems with this argument:

1. A 13 percent drop does not make an effect three times as large seem plausible.

2. The New York City drop was in heart attack deaths, as opposed to heart attacks generally, which was the measure used in the Helena, Montana, study co-authored by Glantz that reported the 40 percent drop. Deaths are affected by changes in treatment as well as changes in risk factors, so you could have a drop in heart attack deaths without a drop in heart attacks.

3. The drop in heart attack deaths continued an accelerating downward trend that began years before the smoking ban took effect. Taking that into account, Siegel calculates that, at most, a 4.6 percent decrease in heart attack deaths could be attributed to the smoking ban.

4. The fact that heart attack deaths dropped after the ban took effect does not mean the ban caused the drop. By the same logic, Siegel writes, you could say the ban "caused a 9.3% reduction in drug and alcohol-related deaths in New York, since the number of deaths from drugs and alcohol dropped by this amount from 2003 to 2004." Maybe people are drinking less because the smoking ban has discouraged them from lingering in bars; maybe the ban has caused people to cut back on smoking and therefore on other forms of drug use associated with it. Or "one could conclude that the smoking ban caused almost a 10% increase in deaths from hypertensive heart disease, since deaths from this cause increased from 1,337 to 1,459 from 2003 to 2004. Perhaps what happened was that smokers, unable to smoke in bars and restaurants, became more anxious and their hypertension worsened." Siegel notes that Glantz has been quick to criticize such post hoc, ergo propter hoc reasoning when it's used to claim that smoking bans hurt business revenue.

Notice, too, that Glantz refers to a "large immediate effect of eliminating exposure to SHS." In a BMJ letter defending the Helena study, by contrast, he and his co-authors say it "is important to emphasize that the observed drop in AMI [acute myocardial infarction]…represents a combination of lower exposure to secondhand smoke as well as the fact that smokefree policies lead some smokers to cut down or quit." Glantz plays up the latter point when he's trying to make his claim seem plausible but ignores it when he's trying to show how dangerous secondhand smoke is. The publicity and press coverage surrounding the Helena study decidedly did not emphasize that the drop in heart attacks might have nothing to do with secondhand smoke, that it could instead be caused by a decrease in smoking.

As I've argued, even the latter explanation is inadequate to explain a drop of 40 percent. Siegel agrees.