Report: Smoking Takes 5 Hours Off Life Expectancy Per Day

A new report attempts to compare the relative effects of habits on life expectancy.

Older current or former heavy smokers may want to consider low-dose CT scans to help screen for lung cancer.

Older current or former heavy smokers may want to consider low-dose CT scans to help screen for lung cancer.

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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.

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"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."

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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 jkoebler@usnews.com.