Scottish smoking ban miracle touches the unborn

The miracles keep on coming in Scotland, soon there will be pilgrimages.

Drop in pregnancy complications after smoking ban

Complications in pregnancy have fallen as a result of the ban on smoking in public places, according to a new study.

Researchers found the ban, introduced almost six years ago, has led to a drop in the number of babies being born before they reach full term.

It has also reduced the number of infants being born underweight.

My word, this post hoc ergo propter hoc junk science sounds like the kind of rubbish Jill Pell keeps coming out with.

The research team, led by Professor Jill Pell...

Ah, Professor Pell, we meet again and under such similar circumstances. You may recall Jill "Pinocchio" Pell from her signature piece claiming that the heart rate plummeted after the Scottish smoking ban, but for sheer effrontery in the face of rock solid evidence, her subsequent article claiming that the asthma rate fell after the smoking ban takes the cake. Rarely has science met fiction so brazenly.

...looked at more than 700,000 single-baby births before and after the introduction of the ban.

The number of mothers who smoked fell from 25.4% to 18.8% after the new law was brought in, researchers discovered.

This, as you might expect from Pell, is a distortion of the truth. The 25.4% figure relates to 2001, some five years before the ban was introduced. Any honest researcher would surely use the figure for 2005 (22.5%) as the pre-ban measure. We already know from a previous Pell study that the ban had no effect on the smoking rate in the general population. Looking at the ISD figures, it is difficult to see any effect on expectant mothers as well. There is a general downward trend which continued after 2006.

The graph above might actually exaggerate the decline. I was interested to see, upon studying the ISD data, that the smoking ban coincided with (I shall not say caused as I am not a charlatan) a large increase in number of expectant mothers for whom no information on smoking status was available. In other words, more pregnant women are refusing to tell the NHS whether or not they smoke.

The likelihood is that many of these women are smokers but do not wish to be chastisted by the denormalisers of Scotland's health service. This suspicion is supported by the fact that the proportion of pregnant women who are lifelong non-smokers has barely moved for a decade.

Back to the news story...

Experts further found there was a drop of more than 10% in the overall number of babies born "pre-term", which is defined as delivery before 37 weeks' gestation.

There was also a 5% drop in the number of infants born under the expected weight, and a fall of 8% in babies born "very small for gestational size".

This is the meat of the research. As so often, the study has been press released before publication so we cannot see which statistical tricks Pell has employed, but we can use the official NHS records to see how her claims stand up. The data are available here.

The graph below shows preterm births (ie. less than 37 weeks gestation) as a percentage of all live births recorded in Scottish hospitals between 1996 and 2010 (the period that Pell claims to have studied).

The proportion of babies born prematurely in this period remained very constant (between 6.8% and 7.9%). The post-smoking ban years were unremarkable, with percentages of 7.3, 7.4, 7.6 and 7.2 (2007, 2008, 2009 and 2010 respectively). The lowest rate was in 1996. There appears to be no relationship with the general smoking rate, maternal smoking rate or the smoking ban.

I suspect what Pell has done here is taken the highest pre-ban figure (7.9%) and compared it with the lowest post-ban figure (7.2%). The difference between these figures in percentage terms is a little under 9% which, with a bit of statistical massaging, could become "a drop of more than 10% in the overall number of babies born 'pre-term'".

Since preterm births are the major driver behind low birth weights, it should be no surprise that there has been no major change in the number of babies with a low birth weight. Between 97.0% and 97.4% of all full-term pregnancies in Scotland in this period resulted in a baby of normal weight (2500 gm+). I can see no evidence of any 'smoking ban effect' in any of the ISD data. There are moderate random variations and nothing more.

Dr Pell said the research highlighted the positive health benefits which can stem from tobacco control legislation.

To paraphrase Mandy Rice-Davis, she would, wouldn't she?

She said: "These findings add to the growing evidence of the wide-ranging health benefits of smoke-free legislation and support the adoption of such legislation in other countries which have yet to implement smoking bans.

"These reductions occurred both in mothers who smoked and those who had never smoked."

Sorry, what?

"These reductions occurred both in mothers who smoked and those who had never smoked."

Doesn't that tell you something then, Pell? If you are claiming that the smoking ban reduced preterm births because it made people give up smoking, the fact that you found the same result with nonsmokers rather gives the game away, does it not? If, on the other hand, you're suggesting that reducing secondhand smoke miraculously reduces preterm births (I haven't read the study yet, but I wouldn't put it past you to indulge in such superstition), the findings for smokers strongly suggest that this is nonsense as well. Or perhaps you are going to claim that smokers somehow feel the benefit of secondhand smoke reductions as well. Nothing would surprise me at this stage.

"The potential for tobacco control legislation to have a positive effect on health is becoming increasingly clear."

Yes, yes. We understand why you keep producing this garbage. Why don't you go find yourself a street corner to shout from?

Researchers looked at data for babies born between January 1996 and December 2009, taken from the Scottish Morbidity Record, which collected information on all women discharged from Scottish maternity hospitals.

Which is exactly what I have shown above. Feel free to check the data yourself.


UPDATE: Michelle Roberts—easily the worst of the BBC's appalling health reporting team—has been suckered by this story. Her entry on Journalisted is an A-Z of pointless epidemiology. I notice the national press have ignored the story, presumably on the basis of 'once bitten'.

Pell's study has appeared on PLoS here. It's short on data but this is her killer graph...

This barely resembles the actual data from Scottish hospitals, but even so it takes a massive leap of faith to attribute the smoking ban to any part of it. The hard line represents the smoking ban, but Pell prefers to use the dotted line because "the Akaike information criterion statistics suggested that using 1 January 2006 as the breakpoint produced a marginally superior model fit than using 26 March 2006." Hey, whatever fits your a priori conclusion the best, Jill.

Even having moved that goalpost, it's plain to see that the fall in preterm births began around ten months before the smoking ban came in. In fact, it came well over a year before, because the timeline Pell is using is the date of conception, not birth. It must have been pretty galling for her to see that the largest drop in her graph preceded the ban and came to an end as soon as the ban came in. Moving the date back to January does not help her much in that respect. Furthermore, even if it had happened after the ban, it would hardly have been proof of anything. There are two little peaks in the graph (as there are in my graph above) followed by two drops. Peaks do tend to be followed by drops, y'know. Maybe Jill Pell should look up 'regression to the mean'.

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The failure of the Scottish smoking ban

A new study in PloS has found that Scotland's smoking ban had no effect on the country's smoking rate in the long term. Authored by the notorious Jill Pell and colleagues from Glasgow University, the study shows that there was an upswing in quit attempts in the months before and after the implementation of the ban (March 2006), but that these attempts had no lasting effect on smoking prevalence.

The graph below, which comes from the PloS study, shows 12 years of smoking prevalence data. The dotted line shows the predicted rate based on past performance. The vertical line shows the smoking ban.

If you look closely, you can see that smoking prevalence dropped below the anticipated level for a while around the time of the ban, but then rose back to the normal level where it has remained ever since.

... in October–December 2005 immediately prior to the introduction of the ban prevalence fell by 1.70% more than expected from the underlying trend. The magnitude of the decay parameter, −0.08, (95% CI −0.38, 0.22) indicates that this effect was short lived with prevalence returning to its long term trend by the last quarter of 2006.

The graph below shows the quantities of nicotine replacement therapy (NRT) being handed out by the Scottish NHS between 2003 and 2009. Again, the dotted line shows the predicted figures.

Assuming that NRT prescriptions are a marker for total quit attempts (a reasonable assumption), there was a rise in people trying to give up around the time of the ban. Quit attempts then fell below the average for the next two years. This suggests that many of the people who would have made a quit attempt in 2007 or 2008 brought their attempt forward to late 2005/early 2006. Having failed to quit at the time of the ban, these people did not try again in the next couple of years. Over the whole period, there was no increase in the number of people who tried to quit.

The rise in quit attempts was no doubt bolstered by the publicity about the ban and the expensive smoking cessation campaigns that accompanied the legislation. As the study's authors note:

In the six months leading up to implementation of the legislation there were two high profile television campaigns.

It was not the ban, but the fear of the ban, combined with increased advertising for smoking cessation services, that led to the increase in quit attempts—this is evident from the fact that the 1.7% drop in smoking prevalence pre-dated the ban by several months. Contrary to the expectations of anti-smoking lobbyists, the ban itself did not help people sustain their quit attempts, nor did it have any independent effect on the smoking rate. Given the choice of giving up smoking or giving up the pub, many of them gave up the pub.

Despite a large surge in the amount of NRT being distributed, there was no lasting effect on smoking prevalence. The short term blip was not sustained in the medium- or long-term. Ultimately, the ban failed to achieve what its advocates hoped and predicted. It also suggests that NRT products are not very good at helping people quit for more than a few weeks or months.

This should all be contrasted with the claims put forward before the ban. In 2005, NHS Scotland's 'evidence-based' review of the literature found that:

Prospective cohort studies reported reductions in smoking prevalence of 7–20% and population-based studies comparing workplaces with and without restrictions showed 15–20% lower prevalence. Partial restrictions had little or no effect. A recent meta-analysis reported a 3.8% reduction in absolute prevalence (pooled effect) associated with smoke-free workplaces.

Given the uncertainty around the precise estimate, the benefit of reduced smoking prevalence has been estimated using conservative estimates of the effect, with a range of 1–3%.

A more conservative estimate would have been 0%. It would have been right.

And let us cast our minds back to 2006 when the BBC reported this breathless forecast from Scotland's Chief Medical Officer...

Ban will 'eradicate lung cancer'

Lung cancer could be virtually wiped out in Scotland as a result of the smoking ban in public places, according to the chief medical officer.

Dr Harry Burns said lung cancer rates would be reduced to just a few hundred cases a year in the future.

Dr Burns said: "Imagining Scotland with no lung cancer is not trivial speculation. In the 1960s, one in 100 men died of lung cancer. Today, rates are falling all the time and thanks to the smoking ban, I expect the reduction in deaths to accelerate until dying from the disease becomes a rare occurrence.

"Anecdotal evidence shows that since the smoking ban, there has been a surge in the numbers of smokers seeking help to give up."

We now know that this "surge" was a temporary blip which was followed by two years of fewer people "seeking help to give up." It turns out that Imperial Tobacco was better at predicting the future than Harry Burns. This, also from 2006...

Imperial not worried by smoke ban

The world's fourth-largest tobacco group, Imperial Tobacco, has said it does not expect UK smoking bans to have a significant impact on business.

"We believe [UK] smokers will continue to choose to smoke regardless of regulations and our view is supported by experiences in other markets," said Imperial.

Can we expect a mea culpa from the anti-smoking campaigners who predicted a huge drop in the number of smokers, if not the elimination of lung cancer? Can we expect them to reassess their strategy in the light of yet another broken promise?

We cannot. As I have said many times, tobacco control is not a results-driven business. As in Ireland, where the smoking rate is now higher than before the ban, the anti-tobacco industry has only one response to failure—more of the same. Pell et al's conclusion epitomises this mindset.

Quit attempts increased in the three months leading up to Scotland's smoke-free legislation, resulting in a fall in smoking prevalence. However, neither has been sustained suggesting the need for additional tobacco control measures and ongoing support.

Heads, we win. Tails, you lose.

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Who do you believe?

Further to Monday's post about the childhood asthma rate in Scotland, it is worth comparing the data presented by Jill Pell in her NEJM paper—which claimed there were 18% fewer hospital admissions after the smoking ban—with the actual hospital admissions data recorded by the Scottish NHS.

This is the "smoothed" graph presented by Pell in her study, which as noted in a previous post, does not even fit her own data. (The last 'year' shown is also not a full year.)

Pell's study produced the intended flood of media coverage, of which this Reuters report was typical.

Scottish smoking ban cuts childhood asthma attacks

A 2006 public smoking ban in Scotland reduced the number of serious childhood asthma attacks by 18 percent per year, researchers reported on Wednesday.

Before the ban imposed in March 2006, the number of hospital admissions for asthma was rising by 5 percent a year among children under 15. The after-ban benefits were seen in both pre-school and school-age children.

Critics had said the ban could force smokers who could not light up in the workplace or in enclosed public spaces to smoke more at home, increasing the risk to children.

Dr. Jill Pell of the University of Glasgow, who worked on the new study, said the findings in the New England Journal of Medicine show that did not happen.

"The evidence we have from Scotland is that it had the opposite effect. People are generally more accepting of the need to protect nonsmokers and vulnerable groups such as children," Pell said in a telephone interview.

"Children were being exposed to less secondhand smoke. We went into the study hoping we would see some health benefit coming out of that."

However...

NHS Scotland has since published the statistics showing how many children were admitted to hospital with asthma between 2005 and 2009. These figures can be viewed here. They do not support Pell's hypothesis in any way, shape or form.

The graph below shows the rate of hospital admissions for asthma for children aged 0-14 years in all Scottish hospitals (per 100,000). The years shown are financial years (April to March - the first year shown is 2005/06), which is useful since the smoking ban was introduced in Scotland at the end of March 2006. Each of the last four bars therefore represent a full post-ban year.

The next graph shows the total number of episodes of the same (ie. the absolute number of admissions). It naturally shows a very similar picture.

Although not discussed by Pell, it is interesting to note that the rate of asthma admissions amongst people of all ages has been higher in every year since the smoking ban was introduced.

And, for good measure, let's have a look at hospital admissions for all diseases of the respiratory system combined.

The data available online do not go back further than 2005/06 so we cannot see the long-term trend earlier in the decade. However, it is sufficient to see that there was no decline in hospital admissions for any of these diseases amongst any age group. If anything, there was an increase.

So, once again, you have a choice. You can choose to believe Jill Pell, a researcher who has, shall we say, "form" when it comes to producing studies like this.

Or you can believe the statistics produced by NHS Scotland which are based on the number of people who actually got admitted to hospital. These statistics, incidentally, support the claim made by Asthma UK that the rate of childhood asthma has remained essentially static for a decade.

It's your call.

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