Sunday, April 23, 2006

More Shoddy Science: First Helena, Then Pueblo, Now Saskatoon

Public health officials from the Saskatoon Health Region (SHR) are telling the media and the public that a 10% decline in the rate of heart attacks in Saskatoon in the first year following the smoking ban is due to the smoking ban.

According to an article in the Star Phoenix: "Public health authorities are crediting Saskatoon's smoking ban with a reduction in the number of heart attacks. ... In the first year of the smoking ban in Saskatoon, the heart attack rate dropped by 10 per cent compared with the previous five years, to 148.2 cases per 100,000 from 165.4 cases for every 100,000 people. That translates into 32 fewer heart attacks in one year, says a report that was received at the authority's meeting."

The Saskatoon smoking ban, which covers all public places, went into effect on July 1, 2004.

The Rest of the Story

Although public health authorities in Saskatoon are bold enough to be making such an assertion that they can directly attribute the 32 fewer heart attacks observed in the city between July 2004 and July 2005 to the smoking ban, they are apparently not so bold as to make the data available for review, which would allow the public to evaluate the validity of the claim and the science upon which the claim is made. While the public health authorities apparently reported their conclusion to the press (a conclusion that is now being rapidly disseminated throughout the world), I can find no evidence that they made the actual data available: the SHR website does not appear to contain a copy of the report so that it can be critically evaluated.

All we know is that there was a 10% reduction in the heart attack rate in Saskatoon from the five years prior to the smoking ban to the year following the ban. That's hardly enough information to be able to draw a causal conclusion about the impact of the smoking ban on the heart attack rate.

For starters, one needs to know the baseline secular trend in heart attacks in Saskatoon. Based on secular trends in heart attacks observed elsewhere, and on the drastic declines in smoking observed in Canada during the late 1990s and early part of the present decade, one would expect that heart attack rates in Saskatoon might have already been on the decline, prior to the implementation of the July 1, 2004 smoking ban. If that's the case, then the 10% decline in heart attacks, or some part of it, might have simply been a reflection of underlying secular trends.

Second, one needs to know the baseline level of variation in heart attacks in Saskatoon from year to year. It's quite possible that an annual variation in heart attacks of about 10% is not unusual for Saskatoon. It's possible that such a change is consistent with normal year-to-year variability in heart attacks in the city.

Third, it's not clear whether there was any comparison group, in which there was not a decline in heart attacks during the same time period, that would provide evidence that might help one to conclude that the observed decline in heart attacks in Saskatoon was attributable to the smoking ban, rather than to secular changes in heart attack incidence, which we know is declining in many large cities.

There has apparently been a significant decline in smoking prevalence in Saskatoon since the implementation of the smoking ban (from 24.1% to 19.4%) and there is apparently survey evidence that this decline is at least partly attributable to the smoking ban. It would not be unreasonable to conclude that the smoking ban affected smoking prevalence in Saskatoon, a finding that would be consistent with extensive published literature on this topic.

However, to make the leap to attributing any changes in heart attack rates to the smoking ban is simply unwarranted unless some rigorous scientific analyses are conducted.

I don't know exactly what scientific analyses have been conducted, because that information was apparently not made available. However, from the limited information that was released to the public, the data are clearly not sufficient to draw a conclusion that the observed decline in heart attacks in Saskatoon was due to the smoking ban. It's not implausible that this is the case (unlike the situation in Helena), especially given the large decline in smoking prevalence; however, the data that are presently available to us are not sufficient to support such a conclusion.

What appears to be happening here is that anti-smoking advocates are so eager to demonstrate an impact of their policies on disease rates that they are jumping the gun in concluding that any changes in disease rates are due to their policies. This is understandable since as public health practitioners, we would all love to see these changes and to believe that they are due to our efforts. However, sometimes we need to hold our eagerness in check in order to ensure that we are relying upon sound science before reporting such conclusions widely to the public.

In Saskatoon, as in Helena and Pueblo, relying upon sound science does not seem to be the priority. The priority appears to be crediting our efforts with any observed changes in disease rates to further support these policies. Unfortunately, while these claims may give a short-term boost to our anti-smoking efforts, in the long run they are going to hurt. Because they are sacrificing the long-term scientific integrity of our movement for short-term political gain. And in the long run, the decline in scientific credibility of our movement is going to hurt a lot more than the fleeting gains from the newspaper coverage of the Saskatoon health officials' claims.

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