A recent national study of the relationship between smoking bans and trends in hospital admissions and mortality should (but probably won't) put a stop to claims that such laws lead to immediate, dramatic reductions in heart attacks. The study, published by the National Bureau of Economic Research (NBER), is by far the largest to be done so far. It covers an eight-year period and includes more than 200,000 admissions for acute myocardial infarction (AMI), plus more than 2 million heart attack deaths in 468 counties across the United States. By contrast, the U.S. studies finding big declines in heart attacks following smoking bans have covered short periods (six months to a year), focused on single locations (such as Helena, Montana, and Pueblo, Colorado), and included hundreds of hospital admissions. Here is what the NBER study's authors, led by the RAND Corporation's Kanaka Shetty, found:
Workplace smoking restrictions are unrelated to changes in all?cause mortality or mortality due to other AMI in all age groups. Restrictions on smoking of any sort are associated with reduced all?cause mortality among the elderly (?1.4%, 95% CI: ?3.0 to 0.2%) but the result is only significant at the 10% level (p=0.06) (see Table 2). We find no statistically significant reduction in admissions due to AMI among working?age adults (?4.2%, 95% CI: ?10.2 to 1.7%, p=0.165) or among the elderly (2.0%, 20 95% CI: ?3.7 to 7.7%, p =0.48) following the enactment of a workplace smoking restriction (see Table 3). We similarly find no evidence of reduction in admissions for other diseases in any age group…
In contrast with smaller regional studies, we find that workplace bans are not associated with statistically significant short-term declines in mortality or hospital admissions for myocardial infarction or other diseases. An analysis simulating smaller studies using subsamples reveals that large short-term increases in myocardial infarction incidence following a workplace ban are as common as the large decreases reported in the published literature.
I italicized that last part because this is what I've been saying for years: In a big country with lots of jurisdictions, there are bound to be places where heart attacks drop substantially after smoking bans are passed. There will also be places where they remain flat or go up. Unless that first category is bigger, there isn't even prima facie evidence that smoking bans reduce heart attacks. But if you focus only on the places where heart attacks do happen to drop sharply, you can trick people into believing such outcomes are typical. Which is what anti-smoking activists like Stanton Glantz have done, and they've done it pretty successfully, judging by their credulous reception in the press. Shetty et al. put it more politely:
Comparisons of small samples…might have led to atypical findings. It is also possible that comparisons showing increases in cardiovascular events after a smoking ban were not submitted for publication because the results were considered implausible. Hence, the true distribution from single regions would include both increases and decreases in events and a mean close to zero, while the published record would show only decreases in events. Thus, publication bias could plausibly explain why dramatic short?term public health improvements were seen in prior studies of smoking bans.
Shetty et al. also note that the sharp drops in heart attacks highlighted by the likes of Glantz were never a biologically plausible result of reducing exposure to secondhand smoke:
The mechanism for these tremendous declines in AMI rates reported in the small?scale studies is unclear…The estimates of risk due to ETS exposure due to public smoking from these small?scale studies are similar in magnitude to those from studies of intensive household exposure to secondhand smoke…The similarity implies exposure to secondhand smoke presents large heath risks at low levels and no additional health risks at higher levels, which seems unlikely.
I would add that the 30 percent risk increase associated with household exposure in those studies seems implausibly large when compared to the heart disease risk associated with smoking, which delivers much higher levels of toxins than breathing air mixed with secondhand smoke. (Smokers are about 100 percent more likely than nonsmokers to develop heart disease and about 70 percent more likely to die from it.) But even if exposure to secondhand smoke does not increase the risk of heart disease, or if smoking bans do not affect exposure much, you would expect them to cause a long-term drop in heart disease to the extent that they encourage smokers to cut back or quit. It just wouldn't happen right away, and it wouldn't be dramatic enough to grab people's attention in the way Glantz likes to do.
More on smoking bans and heart attacks here.
[via The Rest of the Story]