Last September, I mentioned an article in The Sunday Times which signalled that a new smoking ban/heart attack study was marching with ill-deserved confidence in our direction.
The ban on public smoking has caused a fall in heart attack rates of about 10%, a study has found.
Researchers commissioned by the Department of Health have found a far sharper fall than they had expected in the number of heart attacks in England in the year after the ban was imposed in July 2007.
This was truly remarkable news because, as regular readers of this blog and Dr Siegel's blog will know, NHS hospital admissions data clearly show that incidence of acute myocardial infarction (AMI) has continued to decline at the same rate as before the smoking ban.
This posed a problem for Dr Anna Gilmore, the ASH board member who was charged with turning this wholly unexceptional data into a new 'heart miracle'. Earlier junk studies from Scotland (Pell et al., 2008) and Helena, Montana (Sargent, Shephard & Glantz et al., 2004) had claimed a fall in heart attacks of 17% and 40% respectively. Pell did it by ignoring the NHS data set, picking an unusual time-frame and using a very idiosyncratic definition of a heart attack. Glantz did it by simply finding an unusual blip in a very small community.
But all the signs were that Gilmore would be using the full hospital admissions data record for England, which was already available online and which showed that heart attack admissions were falling by less than 5% every year before and after the smoking ban. How would she do it?
In January, I showed England's heart attack data for the second year of the smoking ban. This only confirmed the lack of any effect, and I even apologised for telling you about yet another heart miracle no-show.
The story is always the same, and I apologise for boring readers with one null study after another. But spare a thought for Dr Anna Gilmore, whose job it is to turn this mundane data into a newsworthy study showing that the smoking ban has saved thousands of lives. She may be working on it at this very moment.
The one limitation of the data used by myself and Dr Siegel was that they showed AMI admissions in the financial year (April to March). The smoking ban started on July 1 2007. We still had data for 21 months after the smoking ban, which was more than enough to show that there was no nose-dive in admissions. Still, it would have been better to have the data from July to June.
And now we do, because Anna Gilmore has published her long awaited paper in the British Medical Journal. This is what her figures show:
As expected, there are small discrepancies between the two data sets. (There tends to be slightly more admissions in the April-March set because the timeline goes further back, and Gilmore only shows one year after the ban.) But the story is the same in each—the rate of decline was the same after the ban as it was before.
If you want specifics, here are the figures Gilmore uses (table 1 of the study)...
Emergency AMI admissions in English hospitals
2003/04: 60,680 (a fall of 1.33%)
2004/05: 58,803 (a fall of 3.1%)
2005/06: 55,752 (a fall of 5.19%)
2006/07: 53,964 (a fall of 3.21%)
2007/08: 51,664 (a fall of 4.26%)
As you can see, the decline in admissions in the year after the smoking ban was larger than the year before but smaller than the year before that. In fact, the average in the previous two years was 4.2%—almost exactly what it was in the year after the ban (4.26%).
Faced with this evidence, from a nation of 49 million people, what else can you do but hold up your hands and admit that smoking bans have no perceivable effect on a nation's heart attack rate?
So what's Gilmore's conclusion?
We therefore conclude that the implementation of smoke-free public places is associated with significant reductions in hospital admissions for myocardial infarction
And the accompanying press release reads:
Smokefree legislation linked to drop in admissions for heart attacks
A 2.4 percent drop in the number of emergency admissions to hospital for a heart attack has been observed following the implementation of smokefree legislation in England, researchers from the University of Bath’s Tobacco Control Research Group have found.
The legislation was introduced on 1 July 2007 and this study, funded by the Department of Health and published this week in the British Medical Journal, is the first to evaluate its impact on heart attacks.
The team, led by Dr Anna Gilmore, Director of the Tobacco Control Research Group, part of the UK Centre for Tobacco Control Studies, found there were 1200 fewer emergency hospital admissions for myocardial infarction, commonly known as heart attacks, in the year after the legislation was introduced...
Dr Gilmore said: “Given the large number of heart attacks in this country each year, even a relatively small reduction has important public health benefits. This study provides further evidence of the benefits of smokefree legislation.”
This is a joke, right?
I'm afraid she's serious. Desperate to spin gold from straw, Gilmore throws everything she can at the data. She makes adjustments for surface air temperature, flu seasons, population size and Christmas holidays but she does not address more significant factors like smoking status, diet, exercise or stress (that's not her fault—the NHS does not have this data—but let's not pretend she is isolating smoking in public as the sole uncontrolled risk factor).
None of these calculations are shown or can be verified, but these manipulated data are then fed into a series of computer programs to arrive at an adjusted average daily admissions figure. Although Gilmore uses the July-June figures for all pre-ban years, she goes up to September 2008 for her post-ban year, thereby leaving in July and August, which is when the AMI rate is invariably at its lowest. It's baffling and more than a little suspicious. Why not go up to June 2009? Or at least stop at June 2008?
From this almost incomprehensible mass of heavily adjusted data, she arrives at the figure of 2.4% mentioned above. This 2.4% is the supposed decline in AMI admissions that she directly attributes to the smoking ban. Since the total decline was only 4.26%, this means that the smoking ban was responsible for more than half of the drop; hence the newsworthy but entirely spurious 'smoking ban prevents 1,200 heart attacks' claim.
Although the AMI rate had fallen by 3.21% and 5.19% in 2005/06 and 2006/07, we are expected to believe the decline would only have been 1.86% in 2007/08 if the smoking ban had never happened.
In short, we are expected to believe that there was going to be a smaller than average decline in AMI in 2007/08, and that the smoking ban saved the day. The fact that the decline in AMI was unexceptional in 2007/08 is therefore used as proof that the smoking ban had an exceptional effect!
This is fairy-tale science. It is sheer statistical manipulation and it is breath-taking in it scope and ambition. But then, as I have said before, it always had to be.
More on this tomorrow, I'm sure...