Ever feel a little, well, dumb after a night of distressed or little sleep? There’s a good reason for that. Getting plenty of Z’s is essential to smarts. New research from the University of Wisconsin found that sleep actually replenishes a type of brain cell called myelin (my-uh-linn), possibly explaining the significance of sleep to life itself. The study was performed in mice and found that myelin production was driven by genes and doubled during the REM cycle, the type of sleep linked with dreaming. On the other hand, when the mice were sleep-deprived, genes involved with cell death and stress responses were activated.

Published in the Journal of Neuroscience, the study could give scientists clues about sleep’s role in brain repair and the disease multiple sclerosis. We’ve known for a long time that lack of sleep can seriously impair brain function. For example, sleep helps consolidate memories … meaning if you don’t catch enough winks you’ll have trouble remembering what you experienced during the day. But a foggy memory could be the least of your problems. Chronic sleep loss can also put you at risk for heart disease, high blood pressure, stroke and diabetes — and up to 90 percent of people with insomnia have another health condition. Insomnia also has the strongest link to depression, being one of the most common symptoms. And one study found that depressed people were more likely to sleep less than six hours at night.

If that’s not enough to get you to bed early, consider your vanity: beauty sleep is a real thing. Aside from dark circles under the eyes and sallow skin, chronic sleep loss can lead to more wrinkles and less luster. Lack of sleep increases release of the stress hormone cortisol, which erodes skin collagen and boosts fat production.

So tonight, turn off the T-V, turn in early, and get those much-needed Z’s to stay smart and healthy.