Researchers in Colorado claim to have confirmed the amazing power of smoking bans to reduce heart attacks, a phenomenon first invented discovered in Helena, Montana, in 2003. You may recall that two local physicians, aided by anti-smoking activist Stanton Glantz, reported that Helena's ban was followed by an immediate 60 percent reduction in heart attacks, a claim later downgraded to 40 percent. Now we're told that the heart attack rate in Pueblo, Colorado, fell by 27 percent within 18 months after the city banned smoking in "public places" a couple years ago.

In its press release about the unpublished study, the Pueblo City-County Health Department conflates correlation with causation, saying the data from Helena "showed restrictions on public exposure to secondhand smoke caused a sharp decline in heart attacks." If this had already been demonstrated, why do any more research? In fact, the Helena data indicated only that the ban was followed by a drop in heart attacks, not that the former caused the latter.

The press release also obscures the distinction between reducing secondhand smoke exposure (the ostensible aim of smoking bans) and pressuring smokers to quit (the real aim). It notes that "the study didn't distinguish between smokers and nonsmokers, but rather represented a combination of both smokers and those impacted by secondhand smoke." In other words, some, most, or all of the drop in heart attacks could have occurred among smokers driven to quit by the ban. Yet the press release quotes one researcher who says "this study further validates the argument that limiting exposure to deadly tobacco smoke can save lives" and another who claims "this study provides important knowledge that people can be healthier if secondhand smoke is removed from public places."

As anti-smoking activist (and smoking ban supporter) Michael Siegel points out on his tobacco policy blog, the study does nothing of the kind. Siegel notes that it's quite implausible to suggest that secondhand smoke causes three out of 10 heart attacks. (Even the American Heart Association, which sponsored the conference where the Pueblo data were presented, attributes only 5 percent of heart disease deaths to secondhand smoke.) Siegel suggests the drop in heart attacks was more likely due to a decline in the number of smokers. Yet studies of smokers who quit indicate that their heart attack risk does not fall sharply enough to account for the 27 percent drop ascribed to Pueblo's smoking ban, even if the law caused every smoker in town to quit (which it presumably did not).

In any case, it's not at all clear there's a phenomenon here that needs explaining. Hundreds of cities in the U.S. are covered by state or local smoking bans. I imagine the heart attack rate declined in more than a few after the bans took effect, went up in others, and stayed about the same in most. That's the pattern you'd expect purely by chance. Identifying cities where heart attacks declined proves nothing. If these laws have the sort of impact people like Stanton Glantz are suggesting, there should have been a noticeable post-ban drop pretty much everywhere with similar restrictions.

[Thanks to Linda Stewart for the tip.]