We’ve all been there: We’re up crunching for an exam or can’t catch a wink of sleep on a cross-Atlantic flight. We frequently tell ourselves it’s OK — we’ll crash soon. But can snoozing 10 hours one night make up for the four hours you got the night before?
While You Were Sleeping…The Body and Brain
According to the Centers for Disease Control and Prevention (CDC), adults ages 18 to 60 need at least seven hours of sleep per night. That’s because sleep helps your body and mind restore from the stresses of the day. It might even help your brain consolidate memories. “Sleep specialists no longer think sleep serves a single function,” says Michael Scullin, Ph.D., the study co-author and director of Baylor’s Sleep Neuroscience and Cognition Laboratory. “If we sleep eight hours a night for our whole lives, it must do more — otherwise that’s a really bad use of our time.”
By monitoring brain activity, researchers have found that the brain stays active while it sleeps, though not in the same way across the entire night. You might be familiar with rapid eye movement (REM) — the stage of sleep when you’re dreaming. We complete a cycle of all stages of sleep NREM (non-REM) 1, NREM 2, NREM 3 and REM every 60-90 minutes, Scullin says. “Those stages are also really important in terms of cognitive functioning, consolidating memories and refreshing your brain,” Scullin explains.The duration of each sleep stage changes through the night. So if you’re only getting four hours of sleep, for example, you’ll get very little REM sleep.
Why It’s Basically Impossible to Catch Up on Sleep
If you sleep poorly one night, you’ll feel most of the effects the next day, says Scullin. That said, we’re not always the best judges of our own tiredness. “Sometimes you’ll feel really alert and think you didn’t need sleep at all. But what’s really happening is you’re paying attention to a moment in your circadian rhythm when you’re more awake than normal,” he says.
That’s because there are changes in hormone levels throughout the day, especially melatonin and cortisol — the hormones that control sleep and stress. Your body temperature and blood pressure also change during a 24-hour period. “Because of the fluctuations in these biological rhythms, you could see alertness peak or plummet for a couple of hours at different points during the day,” he explains.
The effects of just one bad night of sleep can last longer than just one day — even after a full night of zzz’s. Scullin points to one study from 2006, where researchers looked at peoples’ brains following one night of sleep deprivation and one night of catch-up sleep. They found that the prefrontal cortex (the area involved in solving complex tasks, attention, memory and sympathy) was impaired.
Another small new study found that students who slept fewer than seven hours three or more nights a week, and caught up on sleep on other nights, had a harder time paying attention, remembering information and being creative. “It’s better to have seven hours consistently than bouncing back and forth between four hours and 10,” says Scullin.
In the short term, poor sleep has also been shown to slow down your metabolism and increase your appetite. What’s worse, it can make you more likely to reach for higher-calorie junk foods — even after just one night. Lack of sleep messes with your mood, too. (Forget not being a morning person.) Some research found that one week of poor sleep makes people more stressed, angry and sad.
That said, all is not lost: If you miss out snoozing you can get back on track. “It’s not that people should never try to catch up. It’s that they should avoid equating cutting back and catching up averages out to be the same, because it doesn’t,” says Scullin.
Here are four scenarios where you might miss out on sleep — and tips on how to get back on track.
4 Sleep-Loss Scenarios, and What to Do About Them
1. You stay up super-late working or studying.
If you’re up late grinding out work, how long does it take to get back on schedule? The occasional sleepless night is like emptying your gas tank. “One night of bad sleep is probably going to have some negative impact on you the next day, whether you recognize it or not,” Scullin says.
What to do: Get two full nights of good sleep. Just one snooze session will only fill you up about three-quarters of the way to normalcy. You won’t be running at full capacity until you get at least one more night of good, consistent sleep, Scullin says. “Think of one bad night of sleep as a sunk cost. You can’t control how you slept last night, but you do have control over how you sleep tonight,” says Scullin.
2. You’re traveling internationally and can’t sleep on the flight.
So you finally booked that Euro trip. The problem is you can’t sleep on the plane. Then, there’s also the time zone issue. While exactly how long it takes to feel normal again varies, Scullin says it takes at least a few days — but you should be back on track within one week. “It’s really tough to switch several time zones and feel perfect the next day. Our bodies weren’t designed that way,” says Scullin. “You’ll adapt, but it takes time, some longer than others.”
What to do: When you’re dealing with a time change, your first instinct might be to sleep the next day away. But it’s better to get as much natural sunlight as quickly as you can — especially in the morning — and follow the current time zone’s schedule immediately. The night you arrive at your destination, make sure you’re sleeping in a dark, quiet room. Avoid alcohol and caffeine, eat healthy foods and drink lots of water on the flight over, he adds.
Scullin says you can also try to “phase advance” your sleep schedule several days before you travel. So if you normally go to bed at 10 p.m., start shutting down at 9 p.m. If that works, snooze another hour earlier at 8 p.m. the following night, and then 7:30 p.m. “I did that a few years ago before traveling to Switzerland,” says Scullin. “I think I was able to phase advance two and half hours, and it really helped me.”
3. You go out with friends all night on Friday and Saturday.
That case of the Mondays could actually be a case of the weekends. That’s because even if you slept in on Sunday after going out all night on Friday and Saturday, your body will be hard-pressed to catch up, says Scullin. “Staying out abnormally late is variability in your sleep schedule, which affects your REM and non-REM sleep, And that changes your circadian rhythms,” Scullin explains. Even if you add a couple of hours on Saturday and Sunday mornings, you’ve shifted your body’s natural sleep rhythms. This can make it harder to fall asleep Sunday night because your body thinks it needs to go to sleep later.
What’s more, consuming too much alcohol impairs your REM sleep, resulting in what Scullin calls an “REM rebound.” Your body will try to make up for lost REM sleep at night, but most REM sleep actually happens in the morning.
What to do: This doesn’t mean you can’t have fun on weekends. “Don’t start the night at midnight and have a dozen drinks,” says Scullin. “Think of sleep as one of the core health behaviors along with eating well and exercising. No one would tell you to eat really well for four or five days of the week but pig out for two or three days. Or exercise regularly for five months but take two months off. Consistency is key for all of these, including sleep,” he says.
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4. You’re a new parent and your baby keeps you up all night.
If you’ve got a newborn in the house, there’s obviously little you can do — at least for a few months. “As the father of an infant, I know all about that!” says Scullin. “Being a new parent means not sleeping well, so just sleep when you can.”
What to do: Scullin says napping (if and when your baby dozes off) can be really helpful. While most sleep specialists emphasize that naps can’t make up for nighttime sleep in the long run, “naps can confer some benefits to cognition. Some studies have shown benefits for fatigue and moodiness,” Scullin says. So hang in there and nap when you can. This, too, shall pass.