The Nuance

Sleep Is the Most Productive Part of the Day

The hours spent sleeping are especially critical for your brain

Markham Heid
Published in
4 min readApr 26, 2019
Illustrations by George Greaves

Every week, the Nuance will go beyond the basics, offering a deep and researched look at the latest science and expert insights on a buzzed-about health topic.

SSleep, you have heard, is essential for human health and development. Newborns and toddlers tend to spend more than half of every day asleep. And while many adults try to get by with less, most people need between seven and nine hours each night in order to perform and feel their best.

While there’s no doubt that sleep is necessary, there’s still a lot about it that befuddles sleep experts. “Despite years of scientific research and studies, we still don’t completely understand why we need to sleep,” says says Dr. Leila Kheirandish-Gozal, a sleep research and professor of pediatrics at the University of Missouri School of Medicine. “We also still don’t know why we dream.”

What experts do know is that sleep is a surprisingly active and fertile time for the brain. Sleep seems to play a crucial role in helping your brain sort, process, store, and make use of the stuff you encounter during your waking hours.

“Some people think of it as a waste of time — as turning the brain off,” says Dr. Carl Bazil, director of the Division of Epilepsy and Sleep at the Columbia University College of Physicians and Surgeons. “But we know now there’s a lot of brain activity going on, and all different types of activity depending on the stage of sleep you’re in.”

Bazil says a pile of research has established that sleep helps people turn short-term memories into durable, long-term ones. And sleep also helps your brain sift out and dispose of the jetsam that’s not worth holding onto, more research suggests.

Sleep also appears to assist the brain with meaning-making and other complex aspects of learning. For example, evidence shows that sleep strengthens “relational memory,” which is a kind of logical, inference-based intelligence that allows people to…



Markham Heid

I’m a long-time contributor at TIME and other media orgs. I write mostly about health. I grew up in Michigan, but these days I live in southwest Germany.