Effects of smoking bans

Over at Offsetting Behaviour Eric notes another very bad analysis of the costs of drugs: in this case, smoking. On a related subject I came across this study on "Changes in U.S. Hospitalization and Mortality Rates Following Smoking Bans" by Kanaka D. Shetty, Thomas DeLeire, Chapin White, and Jayanta Bhattacharya, NBER Working Paper No. 14790, March 2009. The abstract reads,

U.S. state and local governments are increasingly restricting smoking in public places. This paper analyzes nationally representative databases, including the Nationwide Inpatient Sample, to compare short-term changes in mortality and hospitalization rates in smoking-restricted regions with control regions. 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.

The study 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. Some of the conclusions of the study are,

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.

At Reason magazine Jacob Sullum writes,

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.

But smoking bans may still have a positive effect, even if exposure to secondhand smoke does not increase the risk of heart disease or if smoking bans do not affect exposure much, it could still be that they may cause a long-term drop in heart disease to the extent that they encourage smokers to cut back or quit. Of course whether this is the best way to achieve the end is still up for debate.