Meet the micromort

June 15, 2009 at 11:01 pm (science) (, , , , , , , , )

Don’t drink red wine! You’ll increase your risk of colon cancer!

But wait, it also lowers the risk of lung cancer.  Cheers!  Mine’s a large.

The nutritional science media splits things up into those that will kill you and those that will save you.  Sometimes they are the same thing.  How are we to figure out what we should actually eat?

The first thing is that you need to know the absolute magnitude of the affects.  It doesn’t matter if the chance of death is increased by 500% if there was only a one in a million chance of getting it anyway.  Conversely, a modest increase of 20% could be important if your basic risk is high.

David Spiegelhalter of Cambridge University is advocating a new unit of measurement for risk – the micromort. This is a one-in-a-million chance of dying in a day.  We are all exposed in everyday life to a background 50 micromorts of danger – i.e. 50 out of every million people die of normal (but non-natural) causes per day.  Additional activities we do can increase our risk relative to this average.  You need to clock up a further 50 in order to double your chances of dying.

So how can we “spend” our micromorts?  Well, we can travel – 200 miles by car costs 1 micromort, as does 20 miles by bike or a paltry 6 by motorcycle.  However, to measure the real value in doing something you need to allow for all the benefits and dangers.  Its well known that cycling brings health benefits that outweigh the risks when compared to driving, so we must “gain” some morts in fitness benefits. But at least we can compare the risks.

For example, Equasy (addiction to horse riding) is as dangerous as Ecstasy. The risk of dying (in micromorts) for taking a pill of ecstasy is roughly the same (or less) than taking a ride on a horse – both around 1.  Now of course there are other factors – long-term problems associated with addiction to an illegal drug – but the point remains that drug laws cannot be justified on the basis of absolute risks alone.  Some things we think of as dangerous, well, aren’t.  And other things really are.

Returning to the wine, often you don’t get the information needed to calculate risk in a media article.  I couldn’t obviously see the relative risks associated with the wine in the top two articles, for example.  But these numbers are definitely out there, and they can be measured in a simple and clear way.  Why not tell us that, so that we can make an informed decision?

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