Over the last decade, a group of California scientists has quietly amassed the biggest sleep database ever assembled. It includes every dozing off, every wakeup, every REM-cycle, every chunk of deep sleep, from 15 billion nights of human slumber. It can tell us the average person’s bedtime, whether men or women sleep longer, and which city is really the city that never sleeps. These scientists work at Fitbit—the company that sells fitness bands. And for them, revealing your sleep patterns is only the beginning. The longer-term goal of these scientists—and the ones working on the Apple Watch, Garmins, and other wearables—is to spot diseases before you even have symptoms. Diseases of your heart, your brain, your lungs—all picked up by a bracelet on your wrist. But how?

Guests: Eric Friedman, cofounder and CTO of Fitbit. Conor Heneghan, senior research scientist, Google.

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