One-third of Americans are wracking up a debt each night that they may never be able to pay back: sleep debt.

That's where the concept of "catching up on sleep" comes in: You try to squeeze in extra hours of sleep on the days following a bout of poor sleep. For example, sleeping in on the weekends.

But do those extra hours of sleep actually protect you from the health risks of sleep deprivation?

Study results are mixed on the matter, but after checking out the research and chatting with some experts, we can say it seems possible to catch up on sleep, but it's difficult to achieve.

Why it's hard to catch up on sleep

Psychiatrist and sleep medicine expert, Alex Dimitriu, is of the mindset that you can catch up on sleep, but only if you haven't let your sleep debt grow too great. By definition, one hour of sleep lost equals one hour of sleep debt.

"If the sleep debt is greater, the time to recover becomes markedly longer, and complete recovery may not be possible, so it's important to not let sleep debt go too far," Dimitriu, founder of Menlo Park Psychiatry & Sleep Medicine, told Insider.

Keeping your sleep debt in check is important because "long-term, not getting sufficient sleep can lead to medical problems such as obesity, cardiovascular disease, increased risk of cancer, and immune dysfunction," said James A. Rowley, former president of the American Academy of Sleep Medicine Foundation.

Perhaps the most intriguing results of sleep debt and recovery time came from one small study that proposed for every one hour of sleep debt, a person would need four consistent nights of seven to nine hours of quality Zzzs to fully recover.

So, if you need seven hours of sleep per night but only get six during the work week, you'd accumulate five hours of sleep debt come Friday.

According to the study's predictions, this means you'd need about 20 days of consistent quality sleep to fully recover.

So, sleeping in for a few hours on the weekend probably isn't going to fix that.

"While one can make up an hour or two on weekends, one cannot make up getting insufficient sleep for the whole week just by sleeping those extra hours," Rowley said.

That said, in 1963, a then-17-year-old stayed awake for 11 days for a science project. He dealt with temporary nausea and memory loss, but said that after sleeping 14 hours, he felt back to normal.

While that's not an experiment that Dimitriu would like to see his patients or anyone else repeat, it's worth noting that there's more room for studies on how periods of extended sleep affect the health risks of people who are already chronically sleep deprived.

And if the weekend is the only time you can find for sleep, it's "better to increase [sleep hours] on the weekend rather than not doing it at all," biological psychology professor at Stockholm University told Insider's Lyndsay Dodgson.

So what can you do if you're like one-third of Americans who are getting fewer than six hours of sleep a night?

How to pay back sleep debt

Paying back sleep debt is like paying back credit card debt: Try to pay all, or as much, of the total balance so that the debt doesn't grow too large.

That means not waiting until the weekend to try and catch up on an entire week's worth of lost sleep. Instead, if you miss an hour or two of sleep, try making up for it immediately the following day, either with a nap20 to 30 minutes is best – or get a good night's sleep the following evening.

Most important, however, is that you set a sleep schedule and stick to it. "Sleep loves regularity and rhythm," Dimitriu said, because it keeps a consistent circadian rhythm.

Circadian rhythm, often called your internal clock, affects a whole host of important bodily functions, including temperature regulation, hormone control, memory, focus, and – of course – sleep.

Keeping a consistent sleep schedule – aka going to bed and waking up at the same time every day – is one key way to maintaining a healthy circadian rhythm and, subsequently, a healthier you. That's why sleeping in may not be the best option, and brief naps could be better.

Of course, this is all easier said than done, and not everyone can change their schedules to allow for more sleep.

For example, if you're working night shifts, have multiple jobs, or need to get the kids out early in the morning, you're more likely to have sleep debt but have less flexibility to address it. Do the best you can to get as much sleep as possible.

"In those circumstances, even finding an extra 15 minutes per night can be a big difference," Rowley said.

It may also be worth thinking outside the box. For example, a recent study found that when people switched from a 5-day work week to a 4-day work week, the percentage of those getting fewer than seven hours of sleep a night dropped from 42.6 percent to 14.5 percent.

However, you decide to try and pack in more sleep, just remember that sleep isn't a luxury, it's a necessity.

"Sleep should be considered the same as diet and exercise, one of the pillars of overall good health, and should be prioritized just like they are," Rowley said.

This article was originally published by Business Insider.

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