There are lots of reasons why many of us don't get the recommended seven hours or more of sleep each night. Travel schedules, work deadlines, TV bingeing and — a big one — having young children all take a toll.
Research published recently in the journal Sleep finds that up to six years after the birth of a child, many mothers and fathers still don't sleep as much as they did before their child was born. For parents, there's just less time in the day to devote to yourself.
So, can you catch up on sleep? That partly depends on how much sleep you've missed.
A study published in Current Biology points to just how quickly the adverse effects of sleep deprivation can kick in. Researchers at the University of Colorado Boulder recruited a bunch of young, healthy adults who agreed to a stay in a sleep lab. Some were allowed to sleep no more than five hours per night for five consecutive days.
"After five days, people [gained] as much as 5 pounds," says study author Christopher Depner, who studies the links between sleep loss and metabolic diseases. Lack of sleep can throw off the hormones that regulate appetite, he explains, so people tend to eat more.
Depner and his colleagues also documented a decrease in insulin sensitivity among the sleep-deprived participants. "In some people, it decreased to a level where they'd be considered pre-diabetic," he says. Presumably, that rise in blood sugar would be only temporary in these young, healthy people. But it's a striking indicator of how much a lack of sleep can influence metabolism.
And, even after a weekend of catch-up sleep, the participants still gained as much weight as those in the study who had not been allowed to get the extra weekend sleep.
So, bottom line: It can be hard for our metabolism to recover from a week of sleep deprivation, and — over time — chronic sleep loss can increase the risk of Type 2 diabetes.
These findings are eye-opening, but they don't paint the full picture. After all, many of us who lose out on sleep miss only a few hours here or there. Our sleep loss is occasional, not chronic.
Consider this scenario: You have a long day of travel and arrive home late, say, at 2 a.m. And you've got to wake up at the crack of dawn for an early meeting the next day. Is that a big deal?
"The short-term effect is that you're a little more sleepy — your concentration is poor, or [you may lose] words on the tip of your tongue," says Dr. Chris Winter, a sleep specialist in Charlottesville, Va. But what's the long-term effect of one night of partial sleep loss?
"I don't think there really is one," Winter says.
Winter says our bodies are good at compensating for a poor night's sleep. "That correction is probably going to happen fairly quickly," Winter says. "You only got four hours of sleep last night, so you're probably going to sleep quite well the upcoming night."
So, while it's ideal to go to bed and wake up at the same time every day, it's not always possible to stick to this routine. And, a recent longevity study suggests this is OK. "We're very adaptable," Winter says.
Researchers in Sweden looked at how the amount of weekday and weekend sleep was associated with life span. The study included about 44,000 people who were followed for 13 years. The researchers found that people who tended to get less sleep during the week, but who made up for it with extended weekend sleep, did not have an increased risk of premature death. The researchers concluded that "long weekend sleep may compensate for short weekday sleep." They published their findings in the Journal of Sleep Research.
"If you're somebody who needs seven hours of sleep a night, then you really need 49 hours a week," Winter says. In other words, it's probably OK to vary your sleep a bit over a short time period, as long as it averages out to what you need.
"Yes, I do think you can make up for lost sleep," Winter says. "I don't think I'll ever make up for the sleep I lost in medical school and residency, but I do think in the short term you can."
Still, there is one potential drawback of sleeping in on the weekend: Too much sleep can throw off your body clock. So, an hour or two of extra sleep is fine, but you don't want to sleep in so long on a Sunday morning that then it's hard to fall asleep Sunday night.
Another way to recover: Take a nap.
"A 20-minute nap can make up for one hour of lost sleep," says Jim Horne, a sleep researcher and professor emeritus of psychophysiology at Loughborough University in the U.K. He published a study in 2011 demonstrating the benefits of a 20-minute nap.
Horne also points to a review study that concluded that daytime naps can help boost performance — everything from improved memory recall to being more alert. But, here's a tip: Don't take a nap after 3 p.m., or it's likely to interfere with your nighttime sleep.
And Horne has another nap strategy for those times when you want to wake up feeling very alert.
"People call it a caff nap," Horne says. The idea: Lie down to sleep immediately after drinking a cup of coffee.
"That coffee takes 20 minutes to kick in," Horne explains. That's just enough time to catch a few Z's, and it has been shown to be "a very effective combination" for sleepy drivers, he says.
The caffeine-plus-nap strategy now goes by several names. My favorite (with a hat tip to writer Daniel Pink): the nappuccino.
Follow NPR's Allison Aubrey at @AubreyNPRFood.
STEVE INSKEEP, HOST:
Many years ago, I was in a class where a teacher warned that you can never really catch up on lost sleep. That's a common warning. And it sounds kind of grim because lack of sleep is linked to a long list of health risks, everything from anxiety and weight gain to an increased risk of dementia and certain cancers. So is it really true that you can't catch up on lost sleep? And what can those of us who lose a lot of it do? NPR's Allison Aubrey is here to help. She's delved into this topic for a new NPR Life Kit guide to getting good sleep. Allison, thank God you're here.
ALLISON AUBREY, BYLINE: Good morning, Steve.
INSKEEP: What'd you find?
AUBREY: Well, this may not surprise you, but a lot of people are not getting the recommended seven or more hours of sleep each night.
INSKEEP: Holding - I'm holding up my hand. Go on.
AUBREY: (Laughter) I figured you'd be the first one. And when I went to talk to people, I heard a lot of reasons for this. I heard crazy travel schedules, work projects, and another big one - people like Laura Nunn (ph), who have young children.
LAURA NUNN: This is King, and he's 2 1/2.
AUBREY: I met up with a whole bunch of moms. They were at a storytime event held at a local bookstore over at Politics and Prose. And we talked about this new study that finds six years after the birth of a child, parents are still not getting the amount of sleep that they got before they had kids. And Nunn says this really rings true to her. I mean, on nights that she misses out, she says she feels like she's in a fog the next day.
NUNN: It's kind of like a nightmare. It's just like, ugh, where was I? What am I doing? And it takes time to recover from waking up.
AUBREY: Now, a lot of people - like Nunn - try to catch up on less sleep by getting a nap.
NUNN: I definitely feel refreshed and energized.
AUBREY: And another mom that I spoke to who has an infant, she says she tries to just tell herself it'll all be OK. She remembers missing out on sleep back in college.
UNIDENTIFIED PERSON: Partying all night, writing papers in the morning.
NUNN: But now with the kids and jobs, can you ever really recover from lost sleep? That's what people wanted to know.
INSKEEP: It's what I want to know because the question being, if I get extra sleep on the weekend or if I take a nap, does that really help me?
AUBREY: Exactly. That's something that researchers at the University of Colorado have been trying to answer. And in a study that they just published, they recruited a whole bunch of young, healthy people in their 20s and 30s who agreed to spend about two weeks in a sleep lab. And some of them were allowed to sleep no more than five hours a night for five consecutive nights. Now, what the researchers found is that after just five days, a lot of bad things started to happen. I spoke to the study author. His name is Christopher Depner. And he said in the absence of sleep, people start to eat a lot more, especially at night.
CHRISTOPHER DEPNER: So just after five days, people can gain as much as five pounds. And we also see their regulation of their blood sugar - so we call this insulin sensitivity - we see that decreases. And in some people, it decreased to a level where they'd be considered prediabetic by their doctors.
INSKEEP: After a few days?
AUBREY: I know. I mean, to hear that your blood sugar could rise enough, in some cases, to hit this threshold of prediabetes after just five days - I mean, that is not good news, right? So over time, I should say that when these healthy people go back to their healthier lifestyles - including more sleep, presumably - their blood sugar would return to normal. But the finding to note here is that in the short term, these sleepless nights can be really hard to recover from.
I mean, when the people in the study slept in on the weekend, their appetite did go back down. But the big picture here is at the end of the study, they had gained as much weight as people who didn't get that weekend catch-up sleep. And their insulin sensitivity was still off.
INSKEEP: OK, so that doesn't sound good. Is anything good here?
AUBREY: Well, here I have got something that's a little reassuring for you. I mean, we hear this message that it's best to go to bed and wake up at the same time every day. But it's not the reality for most of us. I mean, a lot of us just have interrupted sleep for reasons we can't control.
INSKEEP: The kid is sick. The end.
AUBREY: Exactly. Your flight came in at 3 a.m. You got to be at work the next morning. And a recent study done in Sweden suggests this is OK. Let me talk to you about it. It was a longevity study. It included about 44,000 people. They were followed over 13 years. And what the researchers found is that if you tend to vary your sleep - not these big swings we just heard about in that study, where people were completely sleep deprived for, you know, five nights in a row - we're talking if you tend to miss a few hours here, catch up a few hours on the weekend...
AUBREY: ...That that does not seem to have a negative impact on your longevity. In other words, the people in the study...
AUBREY: ...Who caught up on the weekend, they live just as long.
INSKEEP: Oh - wait a minute. If they caught up on the weekend, they live just as long as someone who slept well, is what you're saying.
AUBREY: As someone who slept more consistently.
AUBREY: OK. So I spoke to a sleep doctor - his name is Chris Winter - about these findings. And here's his sort of big-picture take.
CHRIS WINTER: What I always tell people is if you're somebody who needs seven hours of sleep at night, then you really need 49 hours a week. So as long as you're getting your 49 hours a week, we're very adaptable. And I think you can make up for lost sleep. I do not think that I will ever make up for the sleep I lost in medical school and residency. That's long gone. But I do think that in the short term, you can.
INSKEEP: OK, so trying to catch up on the weekends can help you a little bit. What about napping during the day?
AUBREY: Well, one study found that taking just a 20-minute nap can help you make up for an hour of lost sleep, just in terms of giving you back alertness. So Steve, I want to leave you with a little gift and maybe a new strategy.
AUBREY: I have got a cup of coffee here for you.
INSKEEP: Oh, thank you very much.
AUBREY: It is still warm.
INSKEEP: Ooh, it is warm.
AUBREY: We are going to talk about the caff nap or - it's also been dubbed the nappuccino. Ever heard of it?
INSKEEP: (Laughter) OK, please go ahead.
AUBREY: (Laughter) It's a strategy for a short nap that can leave you feeling alert when you wake up. It was studied in the U.K. back in the '90s. It's actually taught to drivers in the U.K. as a technique to overcome sleepy driving.
AUBREY: What you want to do is you want to take this coffee, drink it, then immediately take a nap. Now after 20 minutes, when the caffeine kicks in - I don't know, nappuccino success.
INSKEEP: Wow. OK, I think I've literally done this without realizing that it was a scientifically proven, good thing to do.
AUBREY: Just don't do this too late in the afternoon. You won't sleep tonight.
INSKEEP: OK. Allison, if you don't mind, I'm going to go get some rest.
AUBREY: Please do.
INSKEEP: NPR's Allison Aubrey with the latest tool from the NPR Life Kit. Allison, thanks for coming by.
AUBREY: Thanks, Steve.
(SOUNDBITE OF BLACK TAFFY'S "GERALDINE") Transcript provided by NPR, Copyright NPR.