Every so often, a scientific report will come out that warns of the life-shortening dangers of smoking, eating red meat, sitting too long, or of drinking too much alcohol. But until now, no researchers have tried to quantify the day-to-day hazards of bad habits.
British statistician David Spiegelhalter, in a report published Monday in British Medical Journal, attempts to quantify which habits have a greater impact on life expectancy: Is drinking heavily worse than living a sedentary lifestyle?
To do this, he created a unit of measure called a "microlife," which corresponds to 30 minutes of life expectancy. Using other studies, he determined that for each day of heavy smoking, a person could be shaving about five hours off his life; someone who watches TV for two hours a day loses about 30 minutes for each day they take part in that activity.
"I'm taking lifelong habits and looking at how they affect people on average, convert it to a daily rate," Spiegelhalter says. "The whole idea is to make a comparison about healthy activities and bad activities. Crudely, drinking two cups of coffee will cancel out eating a burger."
Spiegelhalter says when people hear about life expectancy studies, they assume they'll lose a couple years off the end of their lives. Instead, he says, they should consider it as "aging faster" — a smoker could be hurtling faster towards lung cancer, for instance, than a nonsmoker.
"If you're a smoker, it's like you're moving at your death as if you were living 29 hours a day, it's accelerated aging," he says. "It's a bit of a metaphor — you're getting older quicker rather than living just a bit less."
Here's how different habits stack up, according to Spiegelhalter (estimates are based on various life expectancy studies and hours gained or lost are per day of exposure)
Smoking (15-24 cigarettes per day): -five hours
Alcohol Drinking: First drink, + 30 minutes; -15 minutes per subsequent drink per day
Sedentary behavior: -30 minutes per two hours of TV watching
Eating red meat: -30 minutes per three ounces of red meat consumed
Fruit & vegetables: five servings per day: +two hours
Exercise: +one hour for first 20 minutes, +30 minutes for every additional 40 minutes
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Jason Koebler is a science and technology reporter for U.S. News & World Report. You can follow him on Twitter or reach him at firstname.lastname@example.org.