On the one hand....

Last week I read in the news that sleeping in the afternoon is bad for you. On the very same news feed was an item showing that sleeping in the afternoon is good for you.

This was only unusual in so far as both items turned up on the same day. There are plenty of contradictory stories on anything health-related you care to mention.

Lowering cholesterol is good for your heart...but may give you stomach cancer. Going on the pill protects you from some cancer but increases your risk of others. Drinking wine protects against colds, heart disease, stroke, diabetes, dementia….but increases your risk of breast cancer.

What’s a person to do? Hippie Neil in The Young Ones exhorted his friends not to sleep for fear it would give them cancer. The Telegraph identifies a new food fad - orthorexia - whose suffers are obsessed with "bad" foods and additives, sometimes leaving themselves malnourished in their attempts to avoid certain foodstuffs.

All risks are relative, of course. And the headline may not convey the true facts. As Grandma used to say - everything in moderation.

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One in a million

More on relative risk and quality of information. Phil Bradley's blog alerted me to an item that looks at the incidence of inaccurate data on breast cancer web sites. Apparently 5% of sites looked at contained inaccuracies. The conclusion is that patients should be sceptical of things they read online.

I'd agree that a spot of scepticism is always useful, but it seems to me that the result of this study is that a whopping 95% of websites looked at had no inaccuracies. I find that really heartening - it restores my faith in the quality of online information. Having said that I am, of course, suffering from a common problem here. I haven't read the paper in Cancer that reports the study. I haven't even read the abstract. I've just read the Reuters report on the paper. Did the original paper say how many inaccuracies there were on each of the offending sites? Or how big those inaccuaries were? Or how important? How did they select the sites they looked at? The Reuters report doesn't say.

On a similar theme I've today posted a link on the current awareness page to a paper in JNCI looking at women's perception of risk of recurrence of Ductal Carcinoma In Situ. Women with DCIS are understandably anxious and that leads them to believe that the chances of it recurring are far higher than is actually the case. It's just as well that there is no link between having an anxious - or any other type - of personality, and cancer.

For accurate statistical data on breast and other cancers, Cancer Research UK is a good starting point.

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Presumption of innocence

I once heard a joke about a sheriff who stopped a woman in a car and cautioned her for illegally fishing, because her husband had left his fishing gear in the boot of the car and she was near a river. She was adamant she wasn't intending to fish, but the sheriff replied - "you've got the tackle - how do I know you're not going to use it?" In that case, parried the women, I'm accusing you of rape. The sheriff is gobsmacked - rape?! But he hasn't even touched her!! "I know," replies the women, "but you've got all the tackle - how do I know you're not going to use it?"

In English law we have the concept of the presumption of innocence - more commonly known by the phrase "innocent until proven guilty". The idea is that it's much harder to prove innocence than to prove guilt. If you are guilty the prosecution should be able to find witnesses to your crime, traces of your DNA or fingerprints at the crime scene. If you were home alone last night, no witnesses, no alibi, can you positively prove beyond doubt you were there and not up to no good elsewhere?

Sometimes guilt is easily proved. You were seen by witnesses, you left fingerprints, there are recorded phone conversations or CCTV images. Similarly cause and effect can be easy to demonstrate. Yesterday I walked into the open drawer of my desk (ouch) and today I have a big bruise on my shin. Cause and effect.

It's a little harder with health issues. It took years to link smoking and lung cancer. But it's not possible to say that if you smoke you will die of lung cancer - or that if you don't smoke you wont. Roy Castle, who never smoked, died from lung cancer. Conversely we all know elderly relatives who smoked 40 a day for 60 years or more and died peacefully in their beds of old age.

At the moment scientists keep looking at mobile phone use. So far there is no positive link between phone use and cancer - but is that because there is no link to find? Or because we haven't yet proved the link? Or haven't waited long enough for the cancers to start appearing?

What about aluminium and breast cancer? Various eminent scientists have said that there is no link, although they admit that more research needs to be done. Just because the police haven't yet had time to investigate a crime does it mean that crime hasn't been committed?

The debate that still rumbles on is MMR. MMR stands accused of causing autism. There is plenty of evidence - eyewitness accounts from hundreds of parents who had happy, normal children who were changed into troublesome and troubled children about the time of their MMR vaccine. The judge says that this evidence is circumstantial. Certainly MMR was hanging around looking suspicious - perhaps wearing a hoody and smoking - but that isn't proof that it committed the crime.

Since then their have been endless papers trying to prove MMR's innocence beyond doubt. Today MMR is in the papers again with yet another study failing to prove a link between MMR and autism. Is there no link? Or are scientists asking the wrong questions, looking at the wrong children, or the wrong numbers? (The Guardian calls this latest study "huge" but it only covers 250 children).

The key issues here are risk and evidence.

What is the actual risk of a child developing autism? Of an unvaccinated child catching measles? Of a child dying from measles? How can we understand relative risks? Read Reckoning with Risk, Risk by Lupton and Risk Matters in Healthcare.

And evidence - what is evidence? Are all health interventions guilty until proven innocent? Is it wise to assume every new idea will kill us until we can positively prove otherwise? Is evidence only evidence when it tells us what we want to hear? What value does the experience of ordinary people have in the hierarchy of evidence? If one scientist publishes a paper that says magnets don't relieve arthritis pain, but I can find 50 friends who say they do - who is right? What is good evidence? There are many books in the library on evidence, statistics, reading and understanding papers.

What can any of us do? Be vigilant. Be critical of the evidence. Use our brains.

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