Thursday, February 26, 2009

Official Data Show No Effect of England's Smoking Ban on Heart Attack Admissions During First Nine Months

Christopher Snowdon over at Velvet Glove Iron Fist has reported that data released yesterday by the National Health Service showed that England's smoking ban had no effect on the trend in the number of heart attack admissions during the first nine months that the ban was in effect.

The National Health Service has reported annual summaries of the total number of emergency room admissions for heart attacks or for admissions in which the patient subsequently suffered a heart attack. These data cover all hospitals in England; thus, there are no gaps in the data. The data cover the fiscal year, starting April 1 of the first calendar year and ending March 30 of the second calendar year. Thus, the 2007-2008 data cover the period from April 1, 2007 through March 30, 2008.

The smoking ban in England took effect on July 1, 2007. Thus, although the 2007-2008 data contain figures for three months during which the ban was not yet in effect (April, May, and June), if the ban had any dramatic effect on heart attacks (such as a 27% which is the figure which anti-smoking researchers are citing), one would expect to see some significant acceleration of the existing secular decline in heart attack admissions during the reported 2007-2008 period.

As Snowdon reports, however, there was only a 2% decline in heart attack admissions in England from 2006-07 to 2007-08, compared to a 2.8% decline in the preceding year and a 3.8% decline in the year preceding that. Thus, these data show no evidence that the smoking ban resulted in any significant, immediate decline in heart attacks.

Also as Snowdon reports, these data are very important, because the sample size is huge. Unlike the small sample sizes in studies from Helena, Pueblo, and Bowling Green, the sample size in this England study is larger than all of the published studies combined. In addition, the study covers a long period of time, not just the year before and after the smoking ban (as is the case with some of the published studies).

Further Analysis

It appears that Snowdon included all hospital discharges with a diagnosis of heart attack, both those in which the heart attack was the presenting reason for admission and those cases in which the patient suffered a heart attack subsequent to admission. While there is nothing wrong with this, someone could argue that it is only the admissions for a presenting heart attack that are relevant, because presumably, subsequent heart attacks experienced in the hospital are not triggered by secondhand smoke exposure.

I re-ran the analysis using only hospital admissions for presenting heart attacks (those which presumably might have been triggered by secondhand smoke, as hypothesized by many tobacco control researchers). The data look like this:

As one can see visually, there is absolutely no change in the trend of declining heart attack admissions in England during the first nine months during which the ban was in effect. There appears to be a relatively steady decline in heart attack admissions from 2002-2008, with no change associated with the smoking ban.

The decline in heart attack admissions from 2006-2007 to 2007-2008 was 3.7%, compared to declines of 3.7% in the preceding year and 3.8% in the year before that.

Thus, this analysis confirms that no matter how you look at it, there was no change in the rate of declines in heart attack admissions in England associated with the first nine months of the smoking ban.

The Rest of the Story

These data are important, because they demonstrate the discrepancy between population-based versus anecdotal evidence related to the immediate effect of smoking bans on heart attacks. The studies which have reported an effect of smoking bans on heart attacks have tended to be based on what are essentially anecdotal observations of declines in heart attacks in small cities. In contrast, when one looks systematically at large populations affected by smoking bans, one doesn't find a similar effect. This probably reflects publication bias. It is unlikely that researchers investigating a change in heart attacks following a smoking ban but not finding a substantial decline would publish such a finding.

These data are also important because they demonstrate that, once again, anti-smoking advocates have jumped the gun in prematurely concluding that smoking bans are lowering heart attack rates. We saw this first in Scotland, where researchers and advocates touted a 17% decline in heart attacks in a sample of Scottish hospitals using a specific diagnostic method. However, subsequent population-based data using a consistent diagnostic method revealed that the initial reports were incorrect and there was no significant acute coronary syndrome decline associated with the smoking ban.

Now, we find that anti-smoking advocates in England have jumped the gun. Last June, as I reported here, three anti-smoking groups in England seized upon anecdotal data showing a 40% decline in heart attacks in one hospital trust and used it to publicly claim that the smoking ban was resulting in a dramatic decline in heart attacks. We now know that these claims were wrong; the conclusions were premature and not borne out by the subsequent data.

We now have large population-based studies in England, Wales, and Scotland which fail to show any immediate effect of smoking bans on heart attacks. In light of these studies, which are based on very large sample sizes and which include all hospitals in the relevant areas, it is impossible to stick with the conclusion that smoking bans lead to dramatic, immediate reductions in heart attacks.

It will be interesting to see whether anti-smoking groups in England and elsewhere retract their earlier claims in light of these new data.

As John Maynard Keynes said: "When the facts change, I change my mind. What do you do, sir?"

My suspicion is that the anti-smoking groups will not change with the facts. Based on my experience, they will stick with their premature and inaccurate claims and shift the debate over to the character and integrity of those who are pointing out these conflicting data. They will not deal with the substance of these new findings. Or, at very best, they will acknowledge that the earlier conclusions may have been premature but will take no serious action to disseminate these new data. It's all for a good cause, so why should the truth actually matter?

Let me close with an admission of my own bias here. As someone who has worked for much of my career to promote workplace smoking bans, I would love to see evidence that these bans are resulting in immediate, substantial declines in heart attacks. I'd love to be able to take some credit for an immediate saving of lives. Thus, it is in my personal interest to try to interpret the findings in the most favorable light possible. However, as a scientist, I just cannot come to conclusions which are clearly not supported by the data.

While I firmly believe that in the long run, smoking bans will reduce cardiovascular disease and heart attacks due to long-term changes in smoking prevalence and secondhand smoke exposure, I do not believe there is evidence to conclude that there has been any substantial, immediate decline in heart attack deaths due to these policies.

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