What is 'social jet lag'? NASA scientists reveal why your weekend sleep-in might be wrecking your health

Think jet lag only happens when you fly across time zones? Think again. According to NASA scientists, millions of people are experiencing a form of jet lag every single week—without ever stepping foot on a plane. It's called social jet lag, and it could be the hidden reason you're waking up tired, groggy, and off your game, even after a full night's sleep.

NASA’s Sleep Experts Weigh In
In an interview with The Washington Post, NASA researchers Erin Flynn-Evans and Rachel Jansen explained how astronauts—yes, the people floating in zero gravity with no day or night cycle—manage to get better sleep than many of us here on Earth. And the biggest lesson they’ve learned? Your body clock is sacred, and every time you disrupt it—say, by sleeping in on weekends or pulling late nights—it fights back.

"When you sleep in on weekends, that’s called social jet lag," Jansen said. "It suggests a misalignment with your circadian system." In simpler terms, your internal body clock is out of sync with your lifestyle. The result? Sluggish mornings, poor sleep quality, and a feeling that you’re permanently playing catch-up.

Why Sleeping In Might Be Hurting You
Flynn-Evans explained that this common habit of extra sleep on weekends actually makes you feel worse, not better. “It can make you feel more intense sleep inertia,” she said. That’s the groggy, heavy-limbed sensation you get upon waking. It’s not your mattress or your bedtime app—it’s your body being confused by inconsistent sleep patterns.

A growing body of research supports the idea that social jet lag has real consequences. According to a review in the National Library of Medicine, people suffering from this condition—particularly night owls—tend to sleep poorly during the week and then try to “make up” for it on weekends. The result? Even worse sleep overall.

The Health Risks of Social Jet Lag
Social jet lag isn’t just about being a little drowsy on Monday morning. Studies show it can negatively affect your heart, your weight, your mental health, and even your risk of developing diabetes. Shift workers, who live in a constant state of circadian confusion, often report poorer sleep quality and shorter sleep duration, leading to increased health risks across the board.

In one study using heart rate data, people with greater levels of social jet lag had significantly worse sleep during the workweek than on weekends. And this doesn’t just hurt sleep—it can damage performance, focus, and overall well-being.

Can You Fix It?
Fortunately, there’s hope—and it doesn’t involve moving to space. NASA’s top sleep experts recommend a few surprisingly simple strategies to reset your body clock.

First, try what Jansen calls a “sleep reset.” That means ditching your alarm clock for a few days. “See when you naturally wake up, and how much sleep you get when your body’s fully in charge,” she suggests.

Flynn-Evans, meanwhile, swears by the power of light. “Experiment with bright morning light exposure for a week or more,” she advises. That small change can help realign your circadian rhythm and boost the quality of your sleep long term.

But if you’re still doing everything right—seven to eight hours of sleep, a cool, dark room, a quiet environment—and you’re waking up exhausted, it might be time to call in a pro. “That’s the time to seek help from a sleep doctor,” Flynn-Evans says.

Social jet lag is the silent sleep disruptor most of us never see coming. It disguises itself as a reward—extra rest after a long week—but acts like a thief, stealing your energy, alertness, and long-term health.

The good news? You don’t need to be an astronaut to fix it. You just need to stop treating your circadian rhythm like a snooze button.