It’s a biological fact of life. The birds do it. The bees do it. Even we do it. No, not that.

I’m talking, of course, about sleep, that vital state that lets us recharge and even cleanses the day’s toxins from our brains. But what happens when it doesn’t come easily? And why do some people have an easier time falling and staying asleep than others?

Those are just some of the questions we answer on this week’s episode of Explain It to Me, Vox’s go-to hotline for all the questions you can’t quite answer on your own.

To get to the root of what’s keeping you up at night, we spoke with Jade Wu, a sleep psychologist who specializes in helping people with insomnia. So what constitutes a good sleeper? “It’s more complicated than you would guess, “ Wu says. “We think of getting enough sleep as important for good sleep. But believe it or not, recently some big studies have found that the timing of your sleep can maybe matter even more.”

“If we follow middle-aged people into older age, those who sleep more at more consistent times from day-to-day have lower risk of cancer, heart disease, dementia, and overall mortality,” Wu says. “So it’s about timing, it’s about quality, it’s about quantity, and a host of other factors.” What are those factors? That’s what we tackle this week.

Below is an excerpt of our conversation, edited for length and clarity.

You can listen to Explain It to Me on Apple Podcasts, Spotify, or wherever you get podcasts. If you’d like to submit a question, send an email to askvox@vox.com or call 1-800-618-8545.

What are the big sleep dysfunctions?

The most common problem I see is insomnia, which is just trouble falling asleep or staying asleep. And that can be from a variety of sources. A lot of times it’s a life........

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