An article in the American Heart Association journal Circulation reports that acute coronary events declined in Rome during the first year after Italy's ban on smoking in public places took effect. Looking at hospital discharge records and causes of death, the researchers found that the age-adjusted rate of acute coronary events among 35-to-64-year-olds was 11 percent lower in 2005 than the average for the five years before the ban. The reduction among 65-to-74-year-olds was 8 percent. The researchers attribute these decreases to the smoking ban. "Smoking bans in all public and workplaces result in an important reduction of acute coronary events," says one of the authors. "The smoking ban in Italy is working and having a real protective effect on population health."

A reduction of 8 percent to 11 percent in heart attacks is nothing to sneeze at, but it's a far cry from the 40 percent reduction anti-smoking activists claim occurred in Helena, Montana, as a result of the smoking ban there. (Trying to explain the inconsistency, the authors of the Italian study emphasize the Helena study's weakness, noting that it "counted only 24 hospital admissions for AMI [acute myocardial infarction] from a small community in Montana in the 6 months after the ban.") Attributing even the relatively modest changes seen in Rome to the smoking ban is iffy, since heart attacks were already declining there before the ban. 

In the younger age group, the acute coronary event rate went down from 2000 to 2001, up from 2001 to 2002, and declined steadily thereafter. In the older group, the rate rose steadily from 2000 to 2003, then declined for two years in a row. As Michael Siegel notes on his tobacco policy blog, in both cases there were single-year reductions prior to the smoking ban at least as big as the drop the year afterward. The older group saw a 6 percent drop between 2003 and 2004 (before the ban), the same as the drop between 2004 and 2005 (after the ban). The younger group saw an 8.5 percent drop between 2002 and 2003, compared to a 6.3 percent drop between 2004 and 2005.

So even on their face, these data do not indicate that the smoking ban was associated with an extraordinarily large reduction in heart attacks. If they did, there would still be the question of whether the smoking ban caused the reduction or just happened to precede it. As the researchers concede, the absence of data from a comparable jurisdiction without a smoking ban is a major weakness in the study. Whether as a result of pre-existing (or coinciding) trends or simply by chance, heart attacks are bound to decline in some places after smoking bans take effect; the question is whether they are more likely to fall (or tend to fall more rapidly) in such places than in otherwise similar locations without smoking bans.

I have no doubt that smoking bans, over the long term, will tend to reduce heart attack rates to the extent that they discourage smoking. (The smoking rate in Rome fell from 35 percent to 31 percent among men the year after the ban while remaining about the same among women.) I just think it's highly implausible that the effect would be seen immediately, since epidemiological studies of former smokers show it takes years for their heart disease rates to decline. It's even more implausible that the effect would be due primarily to reductions in exposure to secondhand smoke, as the authors of this study argue. They cite the commonly quoted estimate that secondhand smoke raises the risk of heart disease by 30 percent. But that estimate is derived from epidemiological studies of long-term, intense exposure, mainly among people who live with smokers for decades. Assuming the association indicates a cause-and-effect relationship, you would not expect to see a noticeable decline in risk after one year of smoke-free bars and restaurants.

Even if underlying disease rates don't change that quickly, maybe heart attacks fall because the prevalence of a potential heart attack trigger for people who already have heart disease is reduced. Taken at face value, the numbers from this study imply that something like one in 10 heart attacks among 65-to-74-year-old Italians prior to the ban occurred when they keeled over in smoky bars or restaurants as a result of inhaling tobacco combustion products. I suppose that might be true. But where's the evidence? It's not in this study.