All posts by Adam

Correlation does not equal causation, Dodgy reporting, Public health

The Independent’s anti-vaccine scaremongering

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Last weekend The Independent published a ridiculous piece of antivaccine scaremongering by Paul Gallagher on their front page. They report the story of girls who became ill after receiving HPV vaccine, and strongly imply that the HPV vaccine was the cause of the illnesses, flying in the face of massive amounts of scientific evidence to the contrary.

I could go on at length about how dreadful, irresponsible, and scientifically illiterate the article was, but I won’t, because Jen Gunter and jdc325 have already done a pretty good job of that. You should go and read their blogposts. Do it now.

Right, are you back? Let’s carry on then.

What I want to talk about today is the response I got from the Independent when I emailed the editor of the Independent on Sunday, Lisa Markwell, to suggest that they might want to publish a rebuttal to correct the dangerous misinformation in the original article. Ms Markwell was apparently too busy to reply to a humble reader, so my reply was from the deputy editor, Will Gore.  Here it is below, with my annotations.

Dear Dr Jacobs

Thank you for contacting us about an article which appeared in last weekend’s Independent on Sunday.

Media coverage of vaccine programmes – including reports on concerns about real or perceived side-effects – is clearly something which must be carefully handled; and we are conscious of the potential pitfalls. Equally, it is important that individuals who feel their concerns have been ignored by health care professionals have an outlet to explain their position, provided it is done responsibly.

I’d love to know what they mean by “provided it is done responsibly”. I think a good start would be not to stoke anti-vaccine conspiracy theories with badly researched scaremongering. Obviously The Independent has a different definition of “responsibly”. I have no idea what that definition might be, though I suspect it includes something about ad revenue.

On this occasion, the personal story of Emily Ryalls – allied to the comparatively large number of ADR reports to the MHRA in regard to the HPV vaccine – prompted our attention. We made clear that no causal link has been established between the symptoms experienced by Miss Ryalls (and other teenagers) and the HPV vaccine. We also quoted the MHRA at length (which says the possibility of a link remains ‘under review’), as well as setting out the views of the NHS and Cancer Research UK.

Oh, seriously? You “made it clear that no causal link has been established”? Are we even talking about the same article here? The one I’m talking about has the headline “Thousands of teenage girls enduring debilitating illnesses after routine school cancer vaccination”. On what planet does that make it clear that the link was not causal?

I think what they mean by “made it clear that no causal link has been established” is that they were very careful with their wording not to explicitly claim a causal link, while nonetheless using all the rhetorical tricks at their disposal to make sure a causal link was strongly implied.

Ultimately, we were not seeking to argue that vaccines – HPV, or others for that matter – are unsafe.

No, you’re just trying to fool your readers into thinking they’re unsafe. So that’s all right then.

Equally, it is clear that for people like Emily Ryalls, the inexplicable onset of PoTS has raised questions which she and her family would like more fully examined.

And how does blaming it on something that is almost certainly not the real cause help?

Moreover, whatever the explanation for the occurrence of PoTS, it is notable that two years elapsed before its diagnosis. Miss Ryalls’ family argue that GPs may have failed to properly assess symptoms because they were irritated by the Ryalls mentioning the possibility of an HPV connection.

I don’t see how that proves a causal link with the HPV vaccine. And anyway, didn’t you just say that you were careful to avoid claiming a causal link?

Moreover, the numbers of ADR reports in respect of HPV do appear notably higher than for other vaccination programmes (even though, as the quote from the MHRA explained, the majority may indeed relate to ‘known risks’ of vaccination; and, as you argue, there may be other particular explanations).

Yes, there are indeed other explanations. What a shame you didn’t mention them in your story. Perhaps if you had done, your claim to be careful not to imply a causal link might look a bit more plausible. But I suppose you don’t like the facts to get in the way of a good story, do you?

The impact on the MMR programme of Andrew Wakefield’s flawed research (and media coverage of it) is always at the forefront of editors’ minds whenever concerns about vaccines are raised, either by individuals or by medical studies. But our piece on Sunday was not in the same bracket.

No, sorry, it is in exactly the same bracket. The media coverage of MMR vaccine was all about hyping up completely evidence-free scare stories about the risks of MMR vaccine. The present story is all about hyping up completely evidence-free scare stories about the risk of HPV vaccine. If you’d like to explain to me what makes those stories different, I’m all ears.

It was a legitimate item based around a personal story and I am confident that our readers are sophisticated enough to understand the wider context and implications.

Kind regards

Will Gore
Deputy Managing Editor

If Mr Gore seriously believes his readers are sophisticated enough to understand the wider context, then he clearly hasn’t read the readers’ comments on the article. It is totally obvious that a great many readers have inferred a causal relationship between the vaccine and subsequent illness from the article.

I replied to Mr Gore about that point, to which he replied that he was not sure the readers’ comments are representative.

Well, that’s true. They are probably not. But they don’t need to be.

There are no doubt some readers of the article who are dyed-in-the-wool anti-vaccinationists. They believed all vaccines are evil before reading the article, and they still believe all vaccines are evil. For those people, the article will have had no effect.

Many other readers will have enough scientific training (or just simple common sense) to realise that the article is nonsense. They will not infer a causal relationship between the vaccine and the illnesses. All they will infer is that The Independent is spectacularly incompetent at reporting science stories and that it would be really great if The Independent could afford to employ someone with a science GCSE to look through some of their science articles before publishing them. They will also not be harmed by the article.

But there is a third group of readers. Some people are not anti-vaccine conspiracy theorists, but nor do they have science training. They probably start reading the article with an open mind. After reading the article, they may decide that HPV vaccine is dangerous.

And what if some of those readers are teenage girls who are due for the vaccination? What if they decide not to get vaccinated? What if they subsequently get HPV infection, and later die of cervical cancer?

Sure, there probably aren’t very many people to whom that description applies. But how many is an acceptable number? Perhaps Gallagher, Markwell, and Gore would like to tell me how many deaths from cervical cancer would be a fair price to pay for writing the article?

It is not clear to me whether Gallagher, Markwell, and Gore are simply unaware of the harm that such an article can do, or if they are aware, and simply don’t care. Are they so naive as to think that their article doesn’t promote an anti-vaccinationist agenda, or do they think that clicks on their website and ad revenue are a more important cause than human life?

I really don’t know which of those possibilities I think is more likely, nor would I like to say which is worse.

Dodgy reporting, Dodgy statistics, Economics, Public health

Is smoking plunging children into poverty?

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If we feel it necessary to characterise ourselves as being “pro” or “anti” certain things, I would unambiguously say that I am anti-smoking. Smoking is a vile habit. I don’t like being around people who are smoking. And as a medical statistician, I am very well aware of the immense harm that smoking does to the health of smokers and those unfortunate enough to be exposed to their smoke.

So it comes as a slight surprise to me that I find myself writing what might be seen as a pro-smoking blogpost for the second time in just a few weeks.

But this blogpost is not intended to be pro-smoking: it is merely anti the misuse of statistics by some people in the anti-smoking lobby. Just because you are campaigning against a bad thing does not give you a free pass to throw all notions of scientific rigour and social responsibility to the four winds.

An article appeared yesterday on the Daily Mail website with the headline:

“Smoking not only kills, it plunges children into POVERTY because parents ‘prioritise cigarettes over food'”

and a similar, though slightly less extreme, version appeared in the Independent:

“Smoking parents plunging nearly half a million children into poverty, says new research”

According to the Daily Mail, parents are failing to feed their children because they are spending money on cigarettes instead of food. The Independent is not quite so explicit in claiming that, but it’s certainly implied.

Regular readers of this blog will no doubt already have guessed that those articles are based on some research which may have been vaguely related to smoking and poverty, but which absolutely did not show that any children were going hungry because of their parents’ smoking habits. And they would be right.

The research behind these stories is this paper by Belvin et al. There are a number of problems with it, and particularly with the way their findings have been represented in the media.

The idea of children being “plunged into poverty” came from looking at the number of families with at least one smoker who were just above the poverty line. Poverty in this case is defined as a household income less than 60% of the median household income (taking into account family size). If the amount families above the poverty line spent on cigarettes took their remaining income after deducting their cigarette expenditure below the poverty line, then they were regarded as being taken into poverty by smoking.

Now, for a start, Belvin et al did not actually measure how much any family just above the poverty line spent on smoking. They made a whole bunch of estimates and extrapolations from surveys that were done for different purposes. So that’s one problem for a start.

Another problem is that absolutely nowhere did Belvin et al look at expenditure on food. There is no evidence whatsoever from their study that any family left their children hungry, and certainly not that smoking was the cause. Claiming that parents were prioritising smoking over food is not even remotely supported by the study, as it’s just not something that was measured at all.

Perhaps the most pernicious problem is the assumption that poverty was specifically caused by smoking. I expect many families with an income above 60% of the median spend some of their money on something other than feeding their children. Perhaps some spend their money on beer. Perhaps others spend money on mobile phone contracts. Or maybe on going to the cinema. Or economics textbooks. Or pretty much anything else you can think of that is not strictly essential. Any of those things could equally be regarded as “plunging children into poverty” if deducting it from expenditure left you below median income.

So why single out smoking?

I have a big problem with this. I said earlier that I thought smoking was a vile habit. But there is a big difference between believing smoking is a vile habit and believing smokers are vile people. They are not. They are human beings. To try to pin the blame on them for their children’s poverty (especially in the absence of any evidence that their children are actually going hungry) is troubling. I am not comfortable with demonising minority groups. It wouldn’t be OK if the group in question were, say, Muslims, and it’s not OK when the group is smokers.

There are many and complex causes of poverty. But blaming the poor is really not the response of a civilised society.

The way this story was reported in the Daily Mail is, not surprisingly, atrocious. But it’s not entirely their fault. The research was filtered through Nottingham University’s press office before it got to the mainstream media, and I’m afraid to say that Nottingham University are just as guilty here. Their press release states

“The reserch [sic] suggests that parents are likely to forgo basic household and food necessities in order to fund their smoking addiction.”

No, the research absolutely does not suggest that, because the researchers didn’t measure it. In fact I think Nottingham University are far more guilty than the Daily Mail. An academic institution really ought to know better than to misrepresent the findings of their research in this socially irresponsible way.

Dodgy reporting, Ethics

Chocolate, clueless reporting, and ethics

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I have just seen a report of a little hoax pulled on the media by John Bohannon. What he did was to run a small and deliberately badly designed clinical trial, the results of which showed that eating chocolate helps you lose weight.

The trial showed no such thing, of course, as Bohannon points out. It just used bad design and blatant statistical trickery to come up with the result, which should not have fooled anyone who read the paper even with half an eye open.

Bohannon then sent press releases about the study to various media outlets, many of which printed the story completely uncritically. Here’s an example from the Daily Express.

This may be a lovely little demonstration of how lazy and clueless the media are, but I have a nasty feeling it’s actually highly problematic.

The problem is that neither Bohannon’s description of the hoax nor the paper publishing the results of the study make any mention of ethical review. Let’s remember that although the science was deliberately flawed, there was still a real clinical trial here with real human participants.

What were those participants told? Were they deceived about the true nature of the study? According to Bohannon,

“They used Facebook to recruit subjects around Frankfurt, offering 150 Euros to anyone willing to go on a diet for 3 weeks. They made it clear that this was part of a documentary film about dieting, but they didn’t give more detail.”

That certainly sounds to me like deception. It is an absolutely essential feature of clinical research that all research must be approved by an independent ethics committee. This is all the more important if participants are being deceived, which is always a tricky ethical issue. There is no rule that gives an exception to research done as a hoax.

The research was apparently done under the supervision of a German doctor, Gunter Frank. While I can’t claim to be an expert in professional requirements of German doctors, I would be astonished if running a clinical trial without ethical approval was not a serious disciplinary matter.

And yet there is no mention anywhere of ethical approval for this study. I really, really hope that’s just an oversight. Recruiting human participants to a clinical trial without proper ethical approval is absolutely not acceptable.

Update 29 May:

According to the normally reliable Retraction Watch, my fears about this study were justified. They are reporting that Bohannon had confirmed to them that the study did not have ethical approval.

Also, the paper has mysteriously disappeared from the journal’s website, so I’ve replaced the link to the paper with a link to a copy of it preserved thanks to Google’s web cache and Freezepage.

Conflicts of interest, Dodgy reporting, Dodgy statistics, Public health

Are strokes really rising in young people?

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I woke up to the news this morning that there has been an alarming increase in the number of strokes in people aged 40-54.

My first thought was “this has been sponsored by a stroke charity, so they probably have an interest in making the figures seem alarming”. So I wondered how robust the research was that led to this conclusion.

The article above did not link to a published paper describing the research. So I looked on the Stroke Association’s website. There, I found a press release. This press release also didn’t link to any published paper, which makes me think that there is no published paper. It’s hard to believe a press release describing a new piece of research would fail to tell you if it had been published in a respectable journal.

The press release describes data on hospital admissions provided by the NHS, which shows that the number of men aged 40 to 54 admitted to hospital with strokes increased from 4260 in the year 2000 to to 6221 in 2014, and the equivalent figures for women were an increase from 3529 to 4604.

Well, yes, those figures are certainly substantial increases. But there could be various different reasons for them, some worrying, others reassuring.

It is possible, as the press release certainly wants us to believe, that the main reason for the increase is that strokes are becoming more common. However, it is also possible that recognition of stroke has improved, or that stroke patients are more likely now to get the hospital treatment they need than in the past. Both of those latter explanations would be good things.

So how do the stroke association distinguish among those possibilities?

Well, they don’t. The press release says “It is thought that the rise is due to increasing sedentary and unhealthy lifestyles, and changes in hospital admission practice.”

“It is thought that”? Seriously? Who thinks that? And why do they think it?

It’s nice that the Stroke Association acknowledge the possibility that part of the reason might be changes in hospital admission practice, but given that the title of the press release is “Stroke rates soar among men and women in their 40s and 50s” (note: not “Rates of hospital admission due to stroke soar”), there can be no doubt which message the Stroke Association want to emphasise.

I’m sorry, but they’re going to need better evidence than “it is thought that” to convince me they have teased out the relative contributions of different factors to the rise in hospital admissions.

Correlation does not equal causation, Epidemiology

Obesity and dementia

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It’s always difficult to draw firm conclusions from epidemiological research. No matter how large the sample size and how carefully conducted the study, it’s seldom possible to be sure that the result you have found is what you were looking for, and not some kind of bias or confounding.

So when I heard in the news yesterday that overweight and obese people were at reduced risk of dementia, my first thought was “I wonder if that’s really true?”

Well, the paper is here. Sadly behind a paywall (seriously guys? You know it’s 2015, right?), though luckily the researchers have made a copy of the paper available as a Word document here.

In many ways, it’s a pretty good study. Certainly no complaints about the sample size: they analysed data on nearly 2 million people. With a median follow-up time of over 9 years, their analysis was based on a long enough time period to be meaningful. They had also thought about the obvious problem with looking at obesity and dementia, namely that obese people may be less likely to get dementia not because obesity protects them against dementia, but just because they are more likely to die of an obesity-related disease before they are old enough to develop dementia.

The authors did a sensitivity analysis in which they assumed that patients who died during the observation period had twice the risk of developing dementia had they lived of patients who survived to the end of follow-up. Although that weakened the negative association between overweight and dementia, it was still present.

There are, of course, other ways to do this. Perhaps it might have been appropriate to use a competing risks survival model instead of the Poisson model they used for their statistical analysis, and if you were going to be picky, you could say their choice of statistical analysis was a bit fishy (sorry, couldn’t resist).

But I don’t think the method of analysis is the big problem here.

For a start, although some of the most obvious confounders (age, sex, smoking, drinking, relevant medication use, diabetes, and previous myocardial infarction) were adjusted for in the analysis, there was no adjustment for socioeconomic status or education level, which is a big omission.

But more importantly, I think the major limitation of these results comes from what is known as the healthy survivor effect.

Let me explain.

The people followed up in the study were all aged over 40 at the start. But there was no upper age limit. Some people were aged over 90 at the start. And not surprisingly, most of the cases of dementia occurred in older people.  Only 18 cases of dementia occurred in those aged 40-44, whereas over 12,000 cases were observed in those aged 80-84. So it’s really the older age groups who are dominating the analysis. Over half the cases of dementia occurred in people aged > 80, and over 90% occurred in people aged > 70.

Now, let’s think about those 80+ year olds for a minute.

There is reasonably good evidence that obese people die younger, on average, than those of normal weight. So the obese people who were aged > 80 at the start of the study are probably not normal obese people. They are probably healthier than average obese people. Many obese people who are less healthy than average would be dead before they are 80, so would never have the chance to be included in that age group of the study.

So in other words, the old obese people in the study are not typical obese people: they are unusually healthy obese people.

That may be because they have good genes or it may be because something about their lifestyle is keeping them healthy, but one way or another, they have managed to live a long life despite their obesity. This is an example of the healthy survivor effect.

There will also be a healthy survivor effect at play in the people of normal weight at the upper end of the age range, but that will probably be less marked, as they haven’t had to survive despite obesity.

I think it is therefore possible that this healthy survivor effect may have skewed the results. The people with obesity may have been at less risk of dementia not because their obesity protected them, but because they were a biased subset of unusually healthy obese people.

This does not, of course, mean that obesity doesn’t protect against dementia. Maybe it does. One thing that would have been interesting would be to see the results broken down by the type of dementia. It is hard to believe that obesity would protect against vascular dementia, when on the whole it is a risk factor for other vascular diseases, but the hypothesis that it could protect against Alzheimer’s disease doesn’t seem so implausible.

What it does mean is that we have to be really careful when interpreting the results of epidemiological studies such as this one. It is always extremely hard to know to what extent the various forms of bias that can creep into epidemiological studies have influenced the results.

 

 

Psychology, Publications

Psychology journal bans P values

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I was rather surprised to see recently (OK, it was a couple of months ago, but I do have a day job to do as well as writing this blog) that the journal Basic and Applied Social Psychology has banned P values.

That’s quite a bold move. There are of course many problems with P values, about which David Colquhoun has written some sensible thoughts. Those problems seem to be particularly acute in the field of psychology, which suffers from something of a problem when it comes to replicating results. It’s undoubtedly true that many published papers with significant P values haven’t really discovered what they claimed to have discovered, but have just made type I errors, or in other words, have obtained significant results just by chance, rather than because what they claim to have discovered is actually true.

It’s worth reminding ourselves what the conventional test of statistical significance actually means. If we say we have a significant result with P < 0.05, then that means that there is a 1 in 20 chance we would have seen that result if in fact we had completely random data. A 1 in 20 chance is not at all rare, particularly when you consider the huge number of papers that are published every day. Many of them are going to have type I errors.

Clearly, something must be done.

However, call me a cynic if you like, but I’m not sure how banning P values (and confidence intervals as well, if you thought just banning P values was radical enough) is going to help. Perhaps if all articles in Basic and Applied Social Psychology in the future have robust Bayesian analyses that would be an improvement. But I hardly think that’s likely to happen. What is more likely is that researchers will claim to have discovered effects even if they are not conventionally statistically significant, which surely is even worse than where we were before.

I suspect one of the problems with psychology research is that much research, particularly negative research, goes unpublished. It’s probably a lot easier to get a paper published showing that you have just demonstrated some fascinating psychological effect than if you have just demonstrated that the effect you had hypothesised doesn’t in fact exist.

This is a problem we know well in my world of clinical trials. There is abundant evidence that positive clinical trials are more likely to be published than negative ones. This is a problem that the clinical research community has become very much aware of, and has been working quite hard to solve. I wouldn’t say it is completely solved yet, but things are a lot better now than they were a decade or two ago.

One relevant factor is the move to prospective trial registration.  It seems that prospectively registering trials is helping to solve the problem of publication bias. While clinical research doesn’t yet have a 100% publication record (though some recent studies do show disclosure rates of > 80%), I suspect clinical research is far ahead of the social sciences.

Perhaps a better solution to the replication crisis in psychology would be a system for prospectively registering all psychology experiments and a commitment by researchers and journals to publish all results, positive or negative. That wouldn’t necessarily mean more results get replicated, of course, but it would mean that we’d be more likely to know about it when results are not replicated.

I’m not pretending this would be easy. Clinical trials are often multi-million dollar affairs, and the extra bureaucracy involved in trial registration is trivial in comparison with the overall effort. Many psychology experiments are done on a much smaller scale, and the extra bureaucracy would probably add proportionately a lot more to the costs. But personally, I think we’d all be better off with fewer experiments done and more of them being published.

I don’t think the move by Basic and Applied Social Psychology is likely to improve the quality of reporting in that journal. But if it gets us all talking about the limitations of P values, then maybe that’s not such a bad thing.

 

Dodgy reporting, Public health

Vaping among teenagers

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Vaping, or use of e-cigarettes, has the potential to be a huge advance in public health. It provides an alternative to smoking that allows addicted smokers to get their nicotine fix without exposing them to all the harmful chemicals in cigarette smoke. This is a development that should be welcomed with open arms by everyone in the public health community, though oddly, it doesn’t seem to be. Many in the public health community are very much against vaping. The reasons for that might make an interesting blogpost for another day.

But today, I want to talk about a piece of research into vaping among teenagers that’s been in the news a lot today.

Despite the obvious upside of vaping, there are potential downsides. The concern is that it may be seen as a “gateway” to smoking. There is a theoretical risk that teenagers may be attracted to vaping and subsequently take up smoking. Obviously that would be a thoroughly bad thing for public health.

Clearly, it is an area that is important to research so that we can better understand what the downside might be of vaping.

So I was interested to see that a study has been published today that looks specifically at smoking among teenagers. Can that help to shed light on these important questions?

Looking at some of the stories in the popular media, you might think it could. We are told that e-cigs are the “alcopops of the nicotine world“, that there are “high rates of usage among secondary school pupils” and that e-cigs are “encouraging people to take up smoking“.

Those claims are, to use a technical term, bollocks.

Let’s look at what the researchers actually did. They used cross sectional questionnaire data in which a single question was asked about vaping: “have you ever tried or purchased e-cigarettes?”

The first thing to note is that the statistics are about the number of teenagers who have ever tried vaping. So they will be included in the statistics if they tried it once. Perhaps they were at a party and they had a single puff on a mate’s e-cig. The study gives us absolutely no information on the proportion of teenagers who vaped regularly. So to conclude “high rates of usage” just isn’t backed up by any evidence. Overall, about 1 in 5 of the teenagers answered yes to the question. Without knowing how many of those became regular users, it becomes very hard to draw any conclusions from the study.

But it gets worse.

The claim that vaping is encouraging people to take up smoking isn’t even remotely supported by the data. To do that, you would need to know what proportion of teenagers who hadn’t previously smoked try vaping, and subsequently go on to start smoking. Given that the present study is a cross sectional one (ie participants were studied only at a single point in time), it provides absolutely no information on that.

Even if you did know that, it wouldn’t tell you that vaping was necessarily a gateway to smoking. Maybe teenagers who start vaping and subsequently start smoking would have smoked anyway. To untangle that, you’d ideally need a randomised trial of areas in which vaping is available and areas in which it isn’t, though I can’t see that ever being done. The next best thing would be to look at changes in the prevalence of smoking among teenagers before and after vaping became available. If it increased after vaping became available, that might give you some reason to think vaping is acting as a gateway to smoking. But the current study provides absolutely no information to help with this question.

I’ve filed post this under “Dodgy reporting”, and of course the journalists who wrote about the study in such uncritical terms really should have known better, but actually I think the real fault lies here with the authors of the paper. In their conclusions, they write “Findings suggest that e-cigarettes are being accessed by teenagers more for experimentation than smoking cessation.”

No, they really don’t show that at all. Of those teenagers who had tried e-cigs, only 15.8% were never-smokers. And bear in mind that most of the overall sample (61.2%) were never-smokers. That suggests that e-cigs are far more likely to be used by current or former smokers than by non-smokers. In fact while only 4.9% of never smokers had tried e-cigs, (remember, that may mean only trying them once), 50.7% of ex-smokers had tried them. So a more reasonable conclusion might be that vaping is helping ex-smokers to quit, though in fact I don’t think it’s possible even to conclude that much from a cross-sectional study that didn’t measure whether vaping was a one-off puff or a habit.

While there are some important questions to be asked about how vaping is used by teenagers, I’m afraid this new study does absolutely nothing to help answer them.

 Update 1 April:

It seems I’m not the only person in the blogosphere to pick up some of the problems with the way this study has been spun. Here’s a good blogpost from Clive Bates, which as well as making several important points in its own right also contains links to some other interesting comment on the study.

 

Dodgy statistics

Tobacco vs teddy bears

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Now, before we go any further, I’d like to make one thing really clear. Smoking is bad for you. It’s really bad for you. Anything that results in fewer people smoking is likely to be a thoroughly good thing for public health.

But sadly, I have to say there are times when I think the anti-tobacco movement is losing the plot. One such time came this week when I saw the headline “Industry makes $7,000 for each tobacco death“. That has to be one of the daftest statistics I’ve seen for a long time, and I speak as someone who takes a keen interest in daft statistics.

I’m not saying the number is wrong. I haven’t checked it in detail, so it could be, but that’s not the point, and in any case, the numbers look more or less plausible.

The calculation goes like this. Total tobacco industry profits in 2013 (the most recent year for which figures are available) were $44 billion. In the same year, 6.3 million people died from smoking related diseases. Divide the first number by the second, and you end up with $7000 profit per death.

I think we’re supposed to be shocked by that. Perhaps the message is that the tobacco industry is profiting from deaths. In fact given we are told that this figure has increased from $6000 a couple of years ago as if that were a bad thing, I guess that is what we’re supposed to think.

If you haven’t yet figured out how absurd that is, let’s compare it with the teddy bear industry.

Now, some of the figures that follow come from sources that might not score 10/10 for reliability, and these calculations might look like they’ve been made up on the back of a fag packet.  But please bear with me, because all that we really require for today’s purposes is that these numbers be at least approximately correct to within a couple of orders of magnitude, and I think they probably are.

Let’s start with the number of teddy bear related deaths each year. I haven’t been able to find reliable global figures for that, but according to this website, there are 22 fatal incidents involving teddy bears and other toys in the US each year. Let’s assume that teddy bears account for half of those. That gives us 11 teddy bear related deaths per year in the US.

Since we’re looking at the US, how much profit does the US teddy bear industry make each year? I’ve struggled to find good figures for that, but I think we can get a rough idea by looking at the profits of the Vermont Teddy Bear Company, which is apparently one of the largest players in the US teddy bear market. I don’t know what their market share is. Let’s just take a wild guess that it’s about 1/3 of the total teddy bear market.

The company is now owned by private equity and so isn’t required to report its profits, but I found some figures from the last few years (2001 to 2005) before it was bought by private equity, and its average annual profit for that period was about $1.7 million. So if that represents 1/3 of the total teddy bear market, and if its competitors are similarly profitable (wild assumptions I know, but we’re only going for wild approximations here), then the total annual profits of the US teddy bear market are about £5 million.

So, if we now do the same calculation as for the tobacco industry, we see that the teddy bear industry makes a profit of about $450,000 per death ($5 million divided by 11 deaths).

So do we conclude that the teddy bear industry is far more evil than the tobacco industry?

No. What we conclude is that using “profits per death” as a measure of the social harm of an industry is an incredibly daft use of statistics. You are dividing by the number of deaths, so the more people you kill, the smaller will be your profits per death.

There are many statistics you could choose to show the harms of the tobacco industry. That it kills about half its users is a good place to start.  That chronic obstructive pulmonary disease, a disease that is massively associated with smoking, is the world’s third leading cause of death, also makes a pretty powerful point. Or one of my personal favourite statistics about smoking, that a 35-year-old smoker is twice as likely to die before age 70 as a non-smoker of the same age.

But let’s not try to show how bad smoking is by using a measure which increases the fewer people your product kills, OK?

 

Dodgy advertising, Pseudoscience

How to spot dishonest nutribollocks

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I saw a post on Facebook earlier today from GDZ Supplements, a manufacturer of nutribollocks products aimed at gullible sports people.

The post claimed that “Scientific studies suggest that substances in milk thistle protect the liver from toxins.” This was as part of their sales spiel for their “Milk Thistle Liver Cleanse”. No doubt we are supposed to believe that taking the product makes your liver healthier.

Well, if there really are scientific studies, it should be possible to cite them. So I commented on their Facebook post to ask them. They first replied to say that they would email me information if I shared my email address with them, and then when I asked why they couldn’t simply post the links on their Facebook page, they deleted my question and blocked me from their Facebook page.

Screenshot from 2015-02-21 11:40:18

This, folks, is not the action of someone selling things honestly. If there were really scientific studies that supported the use of their particular brand of nutribollocks, it would have been perfectly easy to simply post the citation on their Facebook page.

But as it is, GDZ Supplements clearly don’t want anyone asking about the alleged scientific studies. It is hard to think of any explanation for that other than dishonesty on GDZ Supplements’ part.

Healthcare, Politics

What my hip tells me about the Saatchi bill

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I have a hospital appointment tomorrow, at which I shall have a non-evidence-based treatment.

This is something I find somewhat troubling. I’m a medical statistician: I should know about evidence for the efficacy of medical interventions. And yet even I find myself ignoring the lack of good evidence when it comes to my own health.

I have had pain in my hip for the last few months. It’s been diagnosed by one doctor as trochanteric bursitis and by another as gluteus medius tendinopathy. Either way, something in my hip is inflammed, and is taking longer than it should to settle down.

So tomorrow, I’m having a steroid injection. This seems to be the consensus among those treating me. My physiotherapist was very keen that I should have it. My GP thought it would be a good idea. The consultant sports physician I saw last week thought it was the obvious next step.

And yet there is no good evidence that steroid injections work. I found a couple of open label randomised trials which showed reasonably good short-term effects for steroid injections, albeit little evidence of benefit in the long term. Here’s one of them. The results look impressive on a cursory glance, but something that really sticks out at me is that the trials weren’t blinded. Pain is subjective, and I fear the results are entirely compatible with a placebo effect. Perhaps my literature searching skills are going the same way as my hip, but I really couldn’t find any double-blind trials.

So in other words, I have no confidence whatsoever that a steroid injection is effective for inflammation in the hip.

So why am I doing this? To be honest, I’m really not sure. I’m bored of the pain, and even more bored of not being able to go running, and I’m hoping something will help. I guess I like to think that the health professionals treating me know what they’re doing, though I really don’t see how they can know, given the lack of good evidence from double blind trials.

What this little episode has taught me is how powerful the desire is to have some sort of treatment when you’re ill. I have some pain in my hip, which is pretty insignificant in the grand scheme of things, and yet even I’m getting a treatment which I have no particular reason to think is effective. Just imagine how much more powerful that desire must be if you’re really ill, for example with cancer. I have no reason to doubt that the health professionals treating me are highly competent and well qualified professionals who have my best interests at heart. But it has made me think how easy it must be to follow advice from whichever doctor is treating you, even if that doctor might be less scrupulous.

This has made me even more sure than ever that the Saatchi bill is a really bad thing. If a medical statistician who thinks quite carefully about these things is prepared to undergo a non-evidence-based treatment for what is really quite a trivial condition, just think how much the average person with a serious disease is going to be at the mercy of anyone treating them. The last thing we want to do is give a free pass for quacks to push completely cranky treatments at anyone who will have them.

And that’s exactly what the Saatchi bill will facilitate.