But if you think American office workers are especially sleep-deprived and powered by caffeine, it turns out we've got nothing on the U.S. military

The CDC says normal humans need eight to nine hours of sleep; about 40 percent of U.S. soldiers get fewer than five. And that's when they're stationed at home, sleeping their "normal" amount. The sleep deprivation gets even more extreme when they're in combat. 

Their primary self-treatment? Coffee, and lots of it--or else caffeine-laden drinks like soda, diet soda, and energy drinks. (Especially Rip It brand energy drinks.)

All of which explains why the U.S. has spent decades studying sleep deprivation. Now, they've pulled it all together in a mathematical formula that can help anyone--military or civilian--figure out the optimal amount of caffeine they need in order to stay alert.

(Also: If you're getting your coffee from a chain like Starbucks, Dunkin' Donuts, or McDonald's, you'll want to check out this comparison of how much caffeine is in coffee from each store's coffee.)

'Continuous sleep deprivation of 60 hours'

This might go down as the latest innovation that was pursued to support the military, but wound up benefiting civilians even more.

Think of the jeep, the jet airplane, penicillin, and now--the caffeine calculator.

I spoke with Dr. Jaques Reifman of the U.S. Army Medical Research and Materiel Command in Fort Detrick, Maryland, co-author of the latest research, which was published in the journal Sleep (pdf link) and covered recently by Jo Craven McGinty in The Wall Street Journal.

"This is leveraging 10 years of research on sleep deprivation," he said. "How do humans respond to continuous sleep deprivation of 60 hours? How is that different from when you sleep three hours a night for 10 days? ... What we're dong here now is to develop math equations that describe the phenomenon."

Specifically, they're coming up with two things:

  • (a) an algorithm that can say how much caffeine the "average" sleep-deprived person needs, in order to be as alert as if they typically got eight hours of sleep, and
  • (b) a way to determine specifically, person-by-person in almost real time, what any particular amount of caffeine will do to their level of alertness.

Two cups of coffee when you wake up

Here are a few examples of what the "average" sleep-deprived person in various situations would have to consume to achieve the same level of alertness they'd have with eight hours of sleep:

  • Getting by on five hours of sleep a night? You might need to consume the equivalent of two cups of weak coffee when you wake up--followed by another two cups, four hours later.
  • Getting reasonable amounts of sleep, but you're working an overnight shift? You'd be best off drinking a quick two cups of weak coffee right at the start of your shift.
  • And, if you're expecting you won't be able to sleep much at all for more than a day or two, you're supposed to drink the equivalent of two cups of coffee at "midnight, 4 a.m., and 8 a.m."

Reifman said the goal here is to squeeze the maximum benefit from the caffeine you're consuming, while making sure the total caffeine in your bloodstream doesn't exceed a threshold of 400 milligrams at any one time.

The "weak cup of coffee" we're talking about has about 100 milligrams of caffeine. For military folks reading this: Seriously, an 8-ounce can of Rip It has about 80 milligrams of caffeine.

There's an app for that

The algorithm that Reifman and his colleagues came up with is proprietary, so the second part of their goal, above--the part where they can tell any person specifically how much caffeine he or she should drink to maximize alertness--isn't something you can use right now.

"The military is trying to license that," Reifman told me. But in the meantime, they've developed a free web app that uses the average data--basically the first of the two goals listed above--so that anybody can use it. You can find that simplified version here.

A downloadable version should also be available soon, Reifman said. Ultimately, he hopes to build something much more robust, that could tell individual soldiers in the field when to consume caffeine so as to achieve maximum alertness in battle.

By the way, I asked Reifman if, given what he's been studying and writing about, he's changed his own sleep and coffee patterns.

"I try to get enough sleep, but there are self-imposed pressures. I need to accomplish so much at work. Sometimes I stay late at work and come in earlier than I should," he said. "But I am trying to practice what I preach, and I do drink a good amount of caffeine."