We hear the admonishments all the time; smoking ___ cigarettes a day will take ___ years off your life, drinking ___ glasses of alcohol a day will take ___ years off your life, sitting for more than ___ hours a day will take ___ years off your life. Yet we smoke, and drink, and sit, and eat too much and exercise too little, and do all those other things that we know will shorten our lives. Why? Well, because those extra years come off the end of our lives, which seems far away and abstract, and we live in the here and now. As often as we worry too much about some smaller risks, we don’t worry enough about the bigger chronic ones that don’t threaten us right away.
But suppose there was some way to see those risks in the here and now, some way to see the life shortening impacts of various choices as we make them, some way to turn the abstraction of the future into the concrete reality of the current moment. Might we make different choices? That is the idea behind the MicroLife, the novel metric invention of David Spiegelhalter, a statistician and the Winton Professor of the Understanding of Risk at the University of Cambridge, who with British journalist Michael Blastland has written a delightful, entertaining, informative book about risk called The Norm Chronicles, in which they lay out the MicroLife as part of their mission to help us overcome our numbers numbness and make smarter healthier choices about risk.
A MicroLife is simply one half hour. That’s it. One half hour. The thing is, you only have so many half hours left. The average American male today will live to age 76. Women will live to 81. So 19 year-old men and 24 year-old women have 57 years left, which comes to about 500,000 hours, which comes to about one million half hours. Each one of those half hours is a MicroLife (micro is the statistical prefix for one million). When you’ve spent your last MicroLife, you die. The question a MicroLife confronts you with is, how do you want to spend them.
Most of our life style choices have implications for longevity that can be expressed in the here and now of MicroLives. By Spiegelhalter’s calculation, every extra 10 pounds above your ideal weight costs you a MicroLife per day. Two cigarettes will cost you one Microlife. So does two hours of sitting on your duff, or every two additional alcoholic drinks beyond the first one (which actually adds a Microlife to your bank account, a benefit you wash away if you keep drinking.) So if MicroLives are like shares of stock and you start with a million, for every lifestyle choice that costs you a MicroLife, imagine taking one share out of your pocket and setting it on fire. (Speaking of setting things on fire, by this calculation, smoking one cigarette will shorten your life by more time than it takes to smoke it.)
Or you could think about it this way. Every day affords you 24 hours, 48 MicroLives. But if you sit at your computer and surf the web reading blogs like this for two hours, have three beers or glasses or wine, and still need to lose that last ten pounds, by the end of that day it’s like you are 25.5 hours older. With MicroLives, you can literally see, choice by choice, how your choices are causing you to age faster.
Conversely, five or more servings of fruits or vegetables a day grants you an extra 4 MicroLives. 20 minutes of moderate physical activity grants you two more. And a cup of coffee, or taking statins to control elevated cholesterol levels, are each worth one. Do all those things in a day and it’s like you have only aged 20 hours. There is some extra sand left in the hourglass, which you can think of as a direct deposit in the bank account of how long you are likely to last.
Spiegelhalter, who is remarkably funny and warm for a British academic immersed in the gloomy statistics of injury and death, is not preachy. He doesn't use the MicroLife to prescribe how we ought to live, just offers it as a tool to help us make more informed choices. Indeed he acknowledges the downside of our obsession with longevity, of living too much of our lives trying to lengthen our lives by giving up the things that make our lives worth living in the first place. Or, as he and Blastland observe in the Norm Chronicles, “a media doctor said ‘I would rather have the occasional bacon sandwich than be 110 and dribbling into my all-bran.’“
The authors are also careful to acknowledge that their MicroLife calculations are based on averages, and so can only provide a general guide for any specific user. Still, the MicroLife has a lot of potential to help us overcome a big problem in the way we deal with risk. While we worry too much about some smaller risks, we usually don’t worry enough about bigger chronic risks because they don’t pose immediate costs. “The MicroLife makes chronic risk a good deal more real and immediate,” Spiegelhalter and Blastland write. It can help us make healthier choices now, before it’s too late. Or as the authors write, “Suddenly chronic risk feels a lot more here and now than the faraway payback that we typically put off thinking about until we’re spent anyway.”