By Brian Carnell

Wednesday, May 21, 2003

One of the sillier junk science claims so far this year was the release of a study that claimed a ban on smoking in Helena, Montana, cut heart attacks in that city by half. I first heard of the widely publicized study in an National Public Radio report that made it sound as if this were sound science, but a close look at the study is more than enough to fall apart.

First, the study is still unpublished and has not been subjected to any sort of peer review.

Second, the study uses obviously questionable methodology. One of the things commonly omitted from many media reports was just how small of a sample size was involved. A finding that heart attacks were cut in half sounds impressive until you look closer and find that we're talking about an area that averaged seven heart attacks a month from 1998-2001. During the six month smoking ban, heart attacks dropped to an average of 4 per month. The value of such small sample size is highly questionable, but doesn't stop researcher Stanley Glantz from declaring in a press release on the study that,

This striking find suggests that protecting people from the toxins in secondhand smoke not only makes life more pleasant; it immediately starts saving lives.

As Jacob Sullum noted in an excellent analysis of the study for Reason,

A little calculation shows how preposterous this claim is, even if you believe that secondhand smoke causes heart disease. The American Heart Association attributes 35,000 heart disease deaths a year, about 5 percent of the total, to secondhand smoke.

It seems reasonable to assume that the proportion would be similar for heart attacks, fatal or not. So even if a city completely eliminated secondhand smoke (which Helena's ban did not do, since it did not apply to smoking at home), how could that possibly cut heart attacks in half?

Sargent and Glantz note that smoking bans also encourage smokers to cut back or quit. Inconveniently for them, that point suggests that any drop in heart attacks could be due to less smoking rather than less exposure to secondhand smoke.

In any case, the numbers still don't add up. According to the U.S. Centers for Disease Control and Prevention, smoking accounts for about one-fifth of heart disease deaths. So even if every smoker in Helena quit (which no one claims happened), you would not get anything like the drop that Sargent, Shepard, and Glantz attribute to the ban.

Sullum also notes that no other locality that has enacted similar bans on smoking has seen any significant drop in heart attacks. California, for example, enacted a workplace smoking ban in 1995 and has not seen the sort of large scale declines in heart attacks that should have followed if Glantz's research was describing a real effect.

What about large scale studies of smoking bans? A large-scale study published in the British Medical Journal suggests that there is no "causal relation between tobacco smoke and tobacco related mortality . . ."

James E. Enstrom, of the University of California at Los Angeles and Geoffrey C. Kabat of the State University of New York at Stony Brook, used survey data from the American Cancer Society that followed 118,000 Californians from 1960-1998.

That study, too, was attacked as being politically motivated. The researchers apparently received money from the tobacco industry, and the American Cancer Society and others complained that the researchers went beyond what the data can say.

The ultimate problem, of course, which tends to get glossed over is the difficulty in accurately determining just how much passive smoke people have been exposed to.

Sources:

Do smoking bans cut heart attacks in half? Jacob Sullum, Reason, April 4, 2003.

Second-hand Smoke Study Sparks Controversy. Mike Wendling, May 16, 2003.

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