Posted by: Phil Peverley1 October 2013
Hardly anyone, either doctor or patient, truly understands the idea of relative risk versus absolute risk. No doubt a few statisticians out there have the concept nailed, but you and I, gentle reader, are not among that number.
We get the idea in theory, but in our day-to-day practice we are as irrational as monkeys on amphetamines. It is ingrained in our genetic make-up. We live in the safest society the world has ever known, yet everywhere we are beset by concerns and fears that make no logical sense. Hence your friends and mine: the Worried Well.
Take one of my patients the other day. ‘I’m worried about aluminium in saucepans, doctor,’ he said (admittedly he wasn’t there to see me for that specific reason). ‘I’ve read that aluminium can cause Alzheimer’s. Can I get a test for aluminium in my blood?’
Probably you can, I dunno. But the sight of a packet of cigarettes sticking out of his top pocket gave me pause. ‘Is that the main thing that you’re worried about?’ I asked him. ‘Well, I don’t want to get Alzheimer’s,’ he countered.
‘Well, me neither. It’s just possible that aluminium from whatever source might, conceivably, raise the probability of Alzheimer’s slightly, but we know for a fact that smoking causes the majority of cases of the rather more common multi-infarct dementia. So why not stop smoking, and then after you’ve done that, you can use the money you’ve saved to buy some new stainless steel pans?’
‘Ah well, smoking calms me down. And my dad smokes and he’s not demented.’ A difficult argument to counter without reaching over and delivering a slap.
Doctors are no better, on the whole. My practice partner once experienced the diagnostic coup of spotting a case of phaeochromocytoma. Nice one kiddo, but he has spent the subsequent 15 years testing all and sundry for it. No luck so far.
One of my patients developed Hodgkin’s lymphoma during pregnancy. Luckily, we spotted it early, but I subsequently discovered only one patient in 8,000 develops Hodgkin’s during pregnancy, which means, at my current consulting rate, I would need another 280 years to spot the next one (although of course I might see her tomorrow). That doesn’t stop me obsessively checking every vague lump in every pregnant woman though.
We really need to start worrying about things that are seriously worrying, rather than ephemera that aren’t. We need to get our children to look both ways before they cross the road, rather than obsess about predatory paedophiles, because getting hit by a car is a real and present danger, while paedophiles aren’t, in relative terms. Not that we should ignore the latter, but we should give the former its due, in terms of actual risk.
Reading Risk: The Science And Politics Of Fear by Dan Gardner would be a step in the right direction. I hope it has made me a little more rational. That said, I read the other day that paper cuts from reading books can turn septic and give you blood poisoning. What to do, what to do?
Dr Phil Peverley is a GP in Sunderland