December 20, 2012
Microlives
It is Christmas, which means that we agonize over the healthiness of our food while over-eating. David Spiegelhalter writes in the BMJ about how to explain the effect of lifestyle risks on lifespan in terms of "microlives" - a millionth of a life, about 30 minutes. Microlives can be gained and lost due to our habits: 2 hours watching television costs you 1 microlife, you gain one for your first drink (of 10 g alcohol) and then lose a half for each subsequent one.
David has a popular explanation at http://understandinguncertainty.org/. It is a neat trick to turn the odds ratios and numbers into something fairly concrete and manageable, a bit like micromorts (which are more suited for one-off risks).
Of course, XKCD has explored the relative time wins of picking up pennies, a related issue. Picking up a penny gives you 12 seconds = 1/195 microlives, implying a microlife is worth $1.95 and your life is worth $1,950,000. The numbers given at understandinguncertainty.org gives a value of £1.70 for a microlife, or $2.77. So clearly UK microlives are valued higher than US microlives (assuming you use NICE and XKCD as your value authorities...) The astonishing thing is that they end up the same order of magnitude, since we are comparing apples and oranges ("comparing health care cost effectiveness evaluations with penny picking" doesn't quite roll off the tongue).