Brian Lair on WNYC, and now we turn to your sleep. Americans are sleeping less than ever,

apparently, about an hour less than their grandparents and great-grandparents did

in the 1940s. And if one hour less doesn't sound like a big deal, they say it can have a big

impact on health. Studies show that an out-of-sync circadian rhythm can raise the risk of anything

from obesity to heart disease, digestive disorders, to depression.

Joining us now with the latest science on our internal clocks and how to use them to improve

sleep and health is Lynn People's science writer and author of a new book called The Inner Clock,

Living in Sync with our circadian rhythms. Lynn, thanks for joining us. Welcome to WNYC. Thanks for having me,

Brian. We've all heard the term, but what's a circadian rhythm? Right. So our bodies are filled

with trillions of these tiny timekeepers, nearly every cell. So in your brain, in your bowels,

your hair follicles, even the muscles of your legs.

And these are all coordinating with each other and with the sun, ideally, to prime the body to do the right things at the right times.

So whether that's sleep, it's also when to metabolize, digest food, when to repair the body, fend off invading pathogens, when you're at

your peak strength or speed to spread away from an enemy. We evolved with these rhythms. And these

are not precision time pieces. So that word circadian, that actually in Latin is circa means

around and DM is day.

So because of that, because our biology is not precisely 24 hours,

to maintain that coordination between our clocks and with the 24 hour Earth day,

we need regular recalibration.

And that's, you know, needing those cues, seeking those signals of

light and dark, incoming food. And this is where we get into trouble. And you describe that

colorfully as, that is the circadian rhythms, as a symphony of miniature timepieces ticking throughout your body.

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