Working The Graveyard Shift, Fighting The Sandman Air traffic controllers are hardly the only workers who struggle to stay awake while working overnight. Sleep researchers say that humans are not designed to be nocturnal, and that the body's clock can never fully adjust to night work.
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Working The Graveyard Shift, Fighting The Sandman

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Working The Graveyard Shift, Fighting The Sandman

Working The Graveyard Shift, Fighting The Sandman

Working The Graveyard Shift, Fighting The Sandman

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  • <iframe src="" width="100%" height="290" frameborder="0" scrolling="no" title="NPR embedded audio player">
  • Transcript

Air traffic controllers are hardly the only workers who struggle to stay awake while working overnight. Sleep researchers say that humans are not designed to be nocturnal, and that the body's clock can never fully adjust to night work.


Joe Palca, science correspondent, NPR
Jeanne Duffy, associate professor of medicine, Harvard Medical School


This is TALK OF THE NATION. Im Neal Conan in Washington.

In recent weeks, more than a few air traffic controllers have been caught napping on the job. A member of the National Transportation Safety Board says on-the-job naps should be considered to help fight fatigue. Secretary of Transportation Ray LaHood says controllers will not be paid to take naps on his watch.

But air traffic controllers are hardly the only people who struggle with the sandman on the overnight. Even if lots of caffeine is consumed, sleep researchers say humans are simply not designed to be nocturnal. Our bodies are generally alert during the day and require sleep at night.

If you work the night shift or have to get up in the middle of the night, tell us how you deal with it. Give us a call, 800-989-8255. Email us, You can also join the conversation on our website. That's at Click on TALK OF THE NATION.

Later in the program, punching out, stories of pilots and crew who have ejected at high speed. But first, sleep and the late-night job. NPR science correspondent Joe Palca joins us here in Studio 3A. And Joe, nice to have you with us.

JOE PALCA: Great to be here.

CONAN: And what have we learned from these cases of the air traffic controllers?

PALCA: Well, I mean, what we've learned is that they're human, too, I guess. As - there's really not a whole lot you can say beside the fact that, you know, as much as politicians want to stamp their feet and shake their fists and do things like that, the human species, as you said, is not nocturnal.

And so if there's someone who works the night shift and is listening to our show right now, they should probably be asleep because...

CONAN: Well, it depends where they are in the country or...

(Soundbite of laughter)

PALCA: I'm not trying to take anything away from the audience, but, no, that's the problem. First of all, we aren't designed to sleep during the day because that's just not our normal rhythm, and you might be able to get away with it if you lived exclusively in artificial light.

But presumably at some point in your day, you pass through a sunlit room or a sunlit exposure, and so there's this mechanism, it's very powerful, that resets your clock to normal day-night schedule, when you get exposed to light.

The best thing, one of the best things, that you can do, I think, is to try to shift and stay on the shift, but inevitably if you're working nights Monday through Friday, and you get the weekend, you want to see your friends, and that means they're not working nights, and so you shift to the day.

And then you're constantly in flux. I mean, you know from that from getting up and doing MORNING EDITION. You know, it's hard to go from morning to normal, back to morning, back to normal.

CONAN: It is. It was very difficult, but I only did it for, what, several months. You know, we both know people who have done if for years, and talk to people like Carl Kasell, who say: Well, you know, I took a nap after I got home. I was up for a little while, went back and took another nap and did it for many years.

PALCA: Right, no, there's strategies that people adopt and, you know, they work to a greater or lesser extent. I mean, one of the things that's going to determine how sleepy you are when you get to the job is how much sleep you got in the last 24 hours.

So if you've learned, over years, to trick your body into thinking that this is a normal schedule, maybe it'll stay fooled. You know, that's the issue.

CONAN: And seven hours of sleep, is that - again, people seem to vary.

PALCA: No, it's all over the map. I think - the only thing I don't believe is people who say that they can only sleep like 15 minutes a night. I think that the studies of those people tend to show that they're - it's not really 15 minutes. It tends to be a lot more like a couple of hours.

But there are, it's a range. You know, I mean, we weren't all stamped out of a cookie-cutter. So there's people who are going to be at each end of the spectrum. Some people, you know, 10 hours is barely sufficient.

CONAN: Do people who work the night shift require more sleep when they get off?

PALCA: It's not a question of more. There's a certain sleep debt, they call it. You need to have whatever you need to have, and if you don't get it, your body is going to keep trying to make you get it. And eventually, your body wins.

CONAN: But even if you've gotten 10, eight, whatever amount of number of hours of sleep you need and go to work on the night shift, you're going to have a problem?

PALCA: Well, that's - yes, that's true. And that issue is really because of this thing called a circadian rhythm. So the circadian rhythm is something as it suggests. It goes around the day, and it has to do with body temperature and release of hormones and various things.

And normally, you're at the lowest point, if you want to think about it in terms of temperature and other things, around four in the morning, three in the morning, in your sleep rhythm, I mean in your circadian rhythm.

And normally that's the place where you're still asleep, and if you're awake, and your circadian rhythm is saying: Hey, Neal, Neal, remember me? I'm telling you to be asleep now. It doesn't matter. It's working against - even if you have had the adequate amount of sleep the day before, it's telling you that you're in the wrong place at the wrong time. That's more like jetlag I think.

CONAN: We want to hear from those of you who are cheating the sandman and up at this hour. If you've worked the overnight shift, give us a call. How do you deal with it? 800-989-8255. Email Chuck's on the line calling us from Sioux City in Iowa.

CHUCK (Caller): Hello, Neal.

CONAN: Hi, Chuck.

CHUCK: Locomotive engineer, 35 years experience. I work for one of the largest freight railroads in the United States, and we were given a two-hour call to report for duty.

CONAN: A two-hour call to report for duty. So you could have gone to sleep at 10 or 11 o'clock at night and then get called at one in the morning?

CHUCK: And sometimes as late as 10 p.m. the next day. It is absolutely impossible to regulate our rest. Consequently, we've been - the Brotherhood of Locomotive Engineers and Trainmen have been fighting this fatigue issue for decades, mostly on deaf ears.

As I told the gentleman earlier, if you find a locomotive engineer that'll tell you that he hasn't fallen asleep on the job, you'll be talking to a liar.

CONAN: And it must be terrifying to wake up in the cab of a locomotive and realize you've been asleep.

CHUCK: Well, there was a recent collision in southern Iowa last week that involved two fatalities, actually in an area where I used to work, and let me just say that it occurred at 7 a.m. They'd probably been on duty since, who knows, 1, 2 a.m. with little advance notice of when they were going to work.

Seven a.m., they're heading into the sun, heading eastward near Red Oak, Iowa, and they collided into the rear of another train at 19 miles an hour. And my guess is fatigue was a factor.

CONAN: Chuck, have you ever fallen asleep in the cab?

CHUCK: Absolutely, absolutely. And we're driving vehicles that are - weigh 18,000 tons, and we're driving them through your community, and quite often, they have hazardous tanks of cars, such as ammonia and et cetera.

CONAN: Is there a backup engineer?

CHUCK: There's another person in the cab. They're usually not qualified to operate the controls.

CONAN: Well, clearly they're qualified to wake you up, though.

CHUCK: Yeah, yes they are.

CONAN: All right, well...

CHUCK: Sometimes that doesn't work.

CONAN: I understand that, Chuck. Thanks very much for the call.

CHUCK: Yeah, thank you.

CONAN: And good luck.

CHUCK: Okay, thank you.

CONAN: And Joe Palca, we thought of air traffic control. Obviously, safety's involved, and Chuck raises another point.

PALCA: Absolutely. I mean, there's a sleep researcher who 25 - even more, 25 or more years ago, named William Dement at Stanford who really you can consider sort of the father of modern sleep research. He did a lot of the very early studies in the '50s, talking about dreams and REM sleep, which you've probably heard of.

He's been banging the drum on this topic for a long time. I mean, this is not a surprise. And the problem is that it's inconvenient for - to make people sleep. I mean, that's why, you know, they want to plug people in at 2 a.m. because they need somebody at 2 a.m. They're not trying necessarily to be mean, but we need somebody.

But that's also why the FAA has some rules about how many hours of consecutive work you can do because they know that eventually, people are going to poop out.

Now, whether they get enough rest, off-time, between shifts, that's another issue. But this has been a problem for a long time, and whether people want to deal with it seriously or when or how, that's been up in the air - forgive me, that's been up in the air.

(Soundbite of laughter)

CONAN: Joining us now from member station WBUR in Boston is Jeanne Duffy, associate professor of medicine at Harvard Medical School and associate neuroscientist at Brigham and Women's Hospital, and nice to have you with us today.

Dr. JEANNE DUFFY (Associate Professor of Medicine, Harvard Medical School): Thank you, it's nice to be here.

CONAN: And do overnight workers ever really adjust to their sleep schedule?

Dr. DUFFY: It's really - most of them never adjust and for some of the reasons that have already been laid out, that on the commute home, typically in the morning, they're exposed to very bright outdoor levels of light, which kind of reinforced their biological clock that it's daytime and time to be awake.

And then also for the reason that on days off, they want to adopt a schedule that allows them to interact with the rest of the world, and so they don't maintain the same night schedule on their days off as they do on workdays.

CONAN: A lot of us hear that phrase, biological clock, and they say: Oh, pshaw, I can power through that.

Dr. DUFFY: You can't override your biology. So I think a lot of us, you know, think that we can do it. And one of the problems is that you're not - often not aware of how impaired you are, how sleepy you are. And at some point, you know, your brain just takes over and transitions you from wakefulness into sleep.

You know, that's why people fall asleep behind the wheel. They certainly wouldn't do that if they thought they were going to fall asleep, right? So they imagine that they can just sort of power through it. But then at some point, it just becomes overwhelming, and you're not aware that it's happening until, you know, until you crash your car into something on the side of the road.

CONAN: So is it unfair to expect locomotive engineers or air traffic controllers or doctors on overnight shifts in emergency rooms to work through the night?

Dr. DUFFY: It's unrealistic to not allow them to do things that will help them to work through the night. So we know that there are many countermeasures that can be used, like brief naps, using caffeine, getting up and walking around.

And if those things are scheduled, and if the time off is scheduled and the shift rotation is scheduled, we know that some of those things can minimize the problems that happen on the night shift.

They can't always eliminate them entirely, but there are many things that can be done to minimize problems on the night shift. But many employers don't take those into account, and, you know, many employees themselves also, you know, work the night shift so that they can do other things during the day. So they don't set aside the time that they should to try to get the amount of sleep that they should.

CONAN: Here's an email we have from David(ph): How does rate power naps, where you go semi-conscious for 15 or 20 minutes but never fall deeply asleep? This is much more refreshing than a nap where you fall relatively deeply asleep for a short period.

Dr. DUFFY: So power naps, so these sort of brief, 20-, 25-minute naps, have been shown to be the most effective things in sort of giving you a pickup and then allowing you to be much more alert for several hours afterwards.

And so for a nap to really work to help someone stay awake for the rest of the night shift, it should be fairly short because if it's too long, you can go into the really deep stages of sleep that, when you come out of them, those are when you feel really groggy.

And so you can something which is called sleep inertia if you fall too deeply asleep, and so that's why very brief naps of, 15, 20, 25 minutes are actually the best and the most refreshing, if you can do that on your break during the night shift.

CONAN: We're talking about sleep or the lack of it. If you work the overnight shift, the rattler, the lobster shift, give us a call, 800-989-8255. Email us, How do you deal with it? I'm Neal Conan. Stay with us. It's the TALK OF THE NATION from NPR News.

(Soundbite of music)

CONAN: This is TALK OF THE NATION. Im Neal Conan in Washington.

We're talking about staying awake on the night shift. Nearly 15 percent of fulltime workers in the U.S. regularly work evening, night or rotating schedules. That's based on 2004 figures from the Labor Department.

Men are more likely than women to work an alternate shift, and blacks more likely than whites, Latinos or Asians. Only a tenth of workers choose an irregular schedule. One thing everybody on those shifts shares is a common lack of good sleep.

If you work the night shift or have to get up in the middle of the night, tell us how you deal with it: 800-989-8255. Email us, You can also join the conversation on our website at Click on TALK OF THE NATION.

NPR science correspondent Joe Palca is with us. There's a link to his story on sleep and the graveyard shift at Also, Jeanne Duffy, a sleep expert and associate professor of medicine at Harvard Medical School. Let's get Dutch(ph) on the line. Dutch is calling us from Paris Island in South Carolina.

DUTCH (Caller): Yes, sir, how are you doing today? Love your show.

CONAN: Thank you.

DUTCH: Yeah, I just wanted to talk a little bit about the force of readiness that we have overseas right now. I'm in the infantry. I'm a combat instructor right now down at Recruit Depot, Parris Island.

And we stay awake on post for - you know, after going on patrol for eight hours a day, sweating all day long, having not a lot of food, not a lot of sleep, not a lot of rest at all, six, seven, eight, nine hours with no moonlight, no kind of sunlight, sitting there staring through our NVGs.

CONAN: Your night-vision goggles, yeah.

DUTCH: Right, right, sorry about that. The thing that makes us stay awake - and I've seen Marines do incredible things, because it's just our sense of purpose of what we're doing for our country and the fear of if we do fall asleep, the consequences of our actions of falling asleep, whether it's us getting killed or everybody inside our friendly lines getting killed.

And what I don't understand is that these air traffic controllers and stuff like that, why they don't have this sense of purpose as well, is that - it's the fear of the consequences of our actions if we fall asleep.

CONAN: And fear, obviously it's your buddies who would be at risk.

DUTCH: Exactly.

CONAN: Yeah. I wonder if you - Jeanne Duffy, if you've thought about that.

Dr. DUFFY: So I haven't thought about that specific situation, but I think to imagine that it's just a matter of will, to be able to will yourself to stay awake, is - you know, it's not just a matter of will.

This is a sort of overwhelming biological need that we have. And it may be in certain situations where, you know, you have sort of a lot of adrenaline because the situation you're in, that that may help you to kind of focus your attention and stay awake.

But it's not true that you can - you know, if you just try hard enough, you don't need to sleep.

CONAN: Dutch, is that your experience? Is it adrenaline, do you think?

DUTCH: Well, the thing is, is I mean after you get your first firefight, second firefight, third firefight, you don't really get that. It kind of goes away. It's kind of like, I guess, doing a drug. You know, you build up a tolerance.

Like I said, it's this sense of purpose. It's - you know, even though after being over there for, you know, seven months in Iraq and then seven months in Afghanistan, you know, you get to a certain point where you're not scared to death, but you just know inside your heart, inside your sense of being, that I cannot fall asleep. Otherwise it'll be detrimental to me, I'll let down my family, I'll let down my friends, and people might get killed.

CONAN: All right, Dutch, thanks very much for the call, appreciate it.

DUTCH: Can I add one thing, please?

CONAN: Sure, go ahead.

DUTCH: Yes, ma'am. This is for the neuroscientist. I've been involved in transcendental meditation and things like this, and I know that we've had brain scans and stuff, and I've gone through, when I haven't had sleep for a long time, and I've gone into states of transcendental meditation for 15 minutes, half hour, and I feel well-rested, like more than if I actually get regular sleep.

Dr. DUFFY: Yeah, so that may be sort of putting your brain into one of these states. It's akin to a power nap, rather than, you know, falling into a deep stage of sleep.

DUTCH: So this does exist? You can actually rejuvenate and revitalize your body through, like you said, a power nap?

Dr. DUFFY: Exactly. It's a short-lasting effect. It won't last you 24 hours. But it will last for several - it can last for several hours after a power nap.


DUTCH: I think this is something that we need to build on as a country and do more research, and I think it could be really good for everybody.


PALCA: Well, I was just going to say, I mean, I don't - I'm not in any way prepared to contradict Dutch's experience of staying awake in this position. But I will say that one thing I learned when I was doing sleep research, before I became a journalist, is that self-reporting is a difficult tool to rely on.

And it is hard to know sometimes, when you have fallen asleep and aren't actually aware of it, and you wake up and maybe you don't even notice that you have fallen asleep.

Now, presumably if you're standing up and, you know, you wake up and you're falling on the ground, then you know something changed. But I'm just saying that a lot of times people say: Oh, I didn't sleep at all last night. And if I go to a sleep lab, you know, I won't sleep at all.

And you put them in bed, and they wake up in the morning, and you say: How did you sleep? Oh, 15 minutes. But if you look at the record, the polygraph record of what their brain is doing, they're asleep two, three, four hours.

So self-reporting, very difficult. And do not think that I am in any way disparaging or disagreeing or not believing what Dutch is saying. I'm simply saying it's hard to evaluate yourself.

DUTCH: (Unintelligible)

Dr. DUFFY: I think that's a really good point because we - in the laboratory studies, when we are recording people's brainwaves, we'll often have them close their eyes, and we can see that they're sleeping and, you know, a few seconds later we'll wake them up because we see that they're asleep and they're not supposed to be.

And they will actually say: Oh, no, I wasn't sleeping. Even though we sort of have the evidence right there in our hands, they have no perception that they were sleeping.

So we can often have these what are called micro-sleep episodes that we are not consciously aware of, and so we think we've managed to stay awake.

CONAN: Dutch, thanks very much for the call.

DUTCH: All right, God bless you. Thank you.

CONAN: Bye-bye. Here's an email from Kevin: I'd like to know if there are people who are naturally inclined to be awake at night, the so-called natural sentinels. Joe, is that anything you've ever heard of?

PALCA: Well, I think Jeanne's probably in a better position to talk about them, but there are certainly people - circadian rhythms are not also fixed in terms of where they occur and how the light actually affects where they start and stop or how they run.

And so there are people who - they call them owls and larks, people who are much better to stay up late and then sleep late, and people who are much better at getting up early in the morning.

And there are even sleep disorders, which Jeanne will know much more about than I, that talk about, you know, how - circadian rhythm disorders, where you really have a hard time keeping your circadian rhythm in the right spot and sleeping in the right time in that spot.

Dr. DUFFY: Right, so there definitely are individual differences in when people's preferred time of sleep is. And we can classify people into sort of early birds and night owls, and night owls are individuals who find it much easier to stay up late night after night and then sleep later in the day, whereas early birds really struggle with that.

An early bird, the sort of early bird type of people are ones who have the most difficulty working the night shift because they not only prefer to go to bed and get up early, but they also have more difficulty sleeping during the daytime than night owl types do.

So there are definitely individual differences in when people are able to sleep and when they prefer to sleep.

CONAN: This email from Christina(ph) in Albany, Oregon: I used to work the night shift at a residential treatment center. It was my job to do general office work, check on inpatients every half hour, and then clean the facility.

It took a while for me not to nearly fall asleep during my eight-hour shift. The harder part was being able to go to sleep once I got off work. That was something of an ordeal, especially since I had children. I have to mention that I did enjoy the shift, if for no other reason than it allowed me to be basically alone. It was the only time I ever had to myself.

Let's go next to Stephanie(ph), Stephanie with us from Portland. Stephanie, are you there?

STEPHANIE (Caller): Yes, I'm here.

CONAN: You're on the air. Go ahead, please.

STEPHANIE: Hi. I am a direct-entry midwife from Portland. So I do out-of-hospital births. And we are on call 24/7. So we get called in whenever, whenever the babies want to come.

And we are up pretty much all night. We are allowed to take naps. There's usually three of us all together working. But we are often up all night or for several nights even, depending on the length of the labor.

So we definitely deal with the situation, and sometimes babies want to come all at once. So we'll have, you know, a couple nights in a row with very little sleep.

CONAN: And how do you deal with it?

STEPHANIE: Well, we fortunately, you know, have kind of the structure to support each other. So you know, working in teams of three, we let each other off for brief spells of sleep, so usually, you know, brief power naps.

And I actually avoid caffeine for long-lasting (unintelligible) my mom's a nurse and she taught me the trick of drinking a lot of water. And I actually drink mint tea to wake up and eat a lot of frequent snacks, so usually things with lots of protein and no sugar, and those things usually work pretty well.

CONAN: Keep your blood sugar up, in any case.

STEPHANIE: Yeah, exactly.

CONAN: Yeah. Jeanne Duffy, that would contribute. If you were hungry as well, that would contribute to falling asleep, you'd think.

Dr. DUFFY: It could, sure. I think that brings up one of the important things about night shift work, which is, you know - because our circadian rhythms are geared to have us being sleeping at night, that there - the rhythms in our metabolism of food are not sort of geared to deal with eating during the night time. And so night shift workers tend to have higher rates of obesity and are more likely to develop things like diabetes, because their eating at a time when their body sort of isn't prepared to deal with that food. Night workers also tend to eat a little - few more calories than day shift workers do, maybe in an attempt to try to keep themselves awake.

CONAN: Stephanie, thanks for the call.

STEPHANIE: Yeah. Thank you.

CONAN: She's a midwife that raises the question: Doctors, who are often, in the old days, were trained, well, in unbelievably brutal shifts in their internships and their residences, stay awake for many hours at a time to supposedly get used to making decisions when they were exhausted. That's been cut back a little bit, Jeanne Duffy. That still goes on to some degree in the medical profession.

Dr. DUFFY: It still goes on to some degree in the medical profession. So there are rules about it for doctors-in-training, but those rules mainly apply to the, sort of, early trainees, but not to the doctors who are still in training and working some of those longer shifts. So there are still, you know, 24-hour shifts that happen to doctors-in-training.

And we, you know - sleep researchers don't believe that you can learn how to make good decisions when you're sleep-deprived. We think that individuals are still impaired, even if they have a lot of experience being sleep-deprived, that their decision-making and their attention is still impaired when they are sleep-deprived.

CONAN: Let's go next to Max, and Max is with us from Des Moines.

MAX (Caller): Hi, Neal. I worked in an emergency room as a social worker overnight, 12-hour shifts. And what I would do - because I only have to work about, oh, maybe four hours out of that 12 hours. There weren't that many patients late at night that had psychiatric emergencies. I would sneak in sleeping bags and pillows and sleep with a cell phone by my side.

So whenever the phone rang, I could pick it up, and I - and if patients came in at six in the morning, I was ready to deal with it. Then I got a new supervisor who had had the same job and would sleep on the job and - but I got fired for sleeping on the job. And I think your expert there makes a good point that people don't make good decisions when they're sleep-deprived.

And I think the issue should be whether the person's able to do their job and how well they're able to their job, not whether they're managing to keep their eyes open all night long.

CONAN: And, Joe, we've seen this, again, in the situation of the air traffic controllers. The secretary of transportation said I'm not going to pay people to nap on my watch, not on the government money. And this is not just that job, but obviously, Max's as well, you know.

PALCA: No. It's - I mean, well, the message seems to be - and we've heard it a couple of times, is you can only go so far in cheating your body. And sleep seems like something - you say, I can deal without that. I mean, we...

CONAN: You sign up for the job, too. Yeah.

PALCA: Yeah. Yeah. But - yeah. And it's not an option. It's not optional. It really needs to be part of a healthy life.

CONAN: We're talking with NPR science correspondent, Joe Palca. Also, Jeanne Duffy, associate professor of medicine at Harvard Medical School, associate neuroscientist at Brigham and Women's Hospital at Harvard Medical School.

And you're listening to TALK OF THE NATION, from NPR News.

Jason's on the line, Jason with us from Myrtle Beach.

JASON (Caller): Hi. Yeah. Thanks, Neal, for taking my call. I really like the show.

CONAN: Sure. Go ahead.

JASON: Well, I don't do this anymore, thank goodness. But I used to work in a hospital, and I used to work 7 p.m. to 7 a.m. shifts, which is - I mean, I was a nurse aid. So if you've done that, you know it's really 6:30 to about 7:30 p.m., or 6:30 p.m. to about 7:30 a.m. And so I'd get home about 8:00, sleep at 9:00, if I was lucky, and then wake back up. Well - and then on the weekends, I would work at a computer lab, a federal government-owned computer lab, and work anywhere from, like. 11 a.m. on through to about 8 p.m., depending - 6 p.m., depending on the day. And sometimes, I had to split shifts there, where I'd work two hours and then off for two, and then on for four, or something like that.

CONAN: And did you get any sleep at all?

(Soundbite of laughter)

JASON: Yeah. It didn't feel like it. Every week, I was swinging, from night to day. And Wednesday were particularly rough, if I work Wednesday night - I'm sorry, Tuesday night at the hospital, and then Wednesday morning get off and then I have to work at the lab, I would only have about three hours of sleep. And then I think that's the day I work in my split shifts, so I'd get three hours of sleep, go to work for two hours, go sleep in my car for two hours, go back to work for, like, four hours, go home and sleep all night and then wake back up, and be pretty much back adjusted to a normal day shift. And then I would work Thursday, Saturday or Thursday, Friday, or whatever.

CONAN: I think, Jeanne Duffy, Jason is describing a - I think it's the ninth level of hell.

(Soundbite of laughter)

Dr. DUFFY: It sounds like it to me.

(Soundbite of laughter)

Dr. DUFFY: Yeah. I mean, our bodies can't make those quick adjustments from day shift to night shift, as anyone who's traveled to another time zone and had jet lag may have experienced. It takes a number of days for your body to make that adjustment. And doing what the caller described doing, I'm sure his clock was, you know, never set to the right time that he was trying to be awake or trying to sleep.

CONAN: He may have a sleep deficit he could probably pay off by 2050 or so.

(Soundbite of laughter)

Dr. DUFFY: Yes.

CONAN: Jason, good luck. Thank you very much for the call.

Here's an email we have from Philippines. It's from Imorris(ph). I'm currently listening to your show in the Philippines, and it's 3:15 in the morning. Luckily, I'm retired and can sleep when I want. I retired because I have really bad insomnia, and I kept falling asleep at work during the day. When you don't have enough sleep and you work during the day, you feel like you're a drunk. I didn't get into trouble because I never got caught sleeping, but I thought I should retire before I got fired.

(Soundbite of laughter)

CONAN: So there are disorders where people have that problem, then can't sleep during the day, right, Jeanne?

Dr. DUFFY: Yes. So there are people who, you know, have time to sleep at night, but find it difficult to, or have maybe a sleep disorder that they're unaware of that disrupts their sleep during the night. And then that, in turn, makes them extremely sleepy during the day. And as well as, you know, people who have day jobs but who only allow themselves - you know, only allocate five or six hours a night, night after night. That sleep deficit builds up, and that can also make you sleepy during the daytime.

CONAN: Well, thanks very much for your time today. We appreciate it. And go home and get a good night's rest.

(Soundbite of laughter)

Dr. DUFFY: Thanks. You, too.

CONAN: Jeanne Duffy is associate professor of medicine in Harvard Medical School, associate neuroscientist at Brigham and Women's Hospital and Harvard Medical School. She joined us from member station WBUR in Boston.

Joe Palca - well, he's got his bicycle clothes on. He's going to race home and get some sleep. Joe, thanks very much.

PALCA: Well, not for a while, but, yes. You're welcome.

CONAN: NPR science correspondent Joe Palca with us here in Studio 3A.

Coming up, when pilots eject from high-performance jets, the Air Force calls it punching out. And there's a relatively small society of pilots who've done it. We'll hear some of their stories next. Stay with us.

I'm Neal Conan. It's the TALK OF THE NATION, from NPR News.

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