How do I get through the day after a bad night?

The alarm is often the worst of it: the moment you have to stand up and meet a day that didn't wait for you to be ready. There may be work ahead, or children to get out of the door, a meeting or a drive, and from here the hours until bedtime can look very long. And there's often a smaller worry about tonight, too: whether it will go the same way. If you only have a minute, you could drink your first coffee where the daylight can reach you, on the back step or at the brightest window in the house.

The groggy, woolly stretch just after the alarm has a name, sleep inertiasleep inertia The groggy, slow feeling just after waking, before the brain is fully up to speed., and it's stronger after a short night⁴4 Trotti, 2017. In one brain-imaging study, it cleared from the front of the brain in between five and thirty minutes⁴. So the way you feel as you first stand up is a poor guide to the hours that follow.

As the morning goes on, what you're most likely to notice are small things: brief lapses where you miss something for a moment³3 Lim & Dinges, 2010. Your reasoning tends to suffer less. Researchers pooled studies that kept people awake for up to two days, far longer than one short night. Even then, any change to reasoning was small enough to be uncertain³. One short night likely takes less still.

You may feel flatter too. What sleep loss takes most is cheerfulness, energy and interest⁵5 Tomaso et al., 2021. If you're short with people today, or everything looks a little gray, you can put much of that down to the night.

Through the day, sleepiness tends to rise and fall. Many people have a dip in alertness in the mid-afternoon⁶6 Monk, 2005. It comes from the body clockbody clock The timekeeper in your brain that runs on a cycle of about a day, setting when you feel sleepy and when you feel alert. Daylight, especially in the morning, keeps it in step with the clock on the wall., and it arrives whether you've had lunch or not, though a heavy, starchy lunch can deepen it. On an ordinary day the urge to sleep then eases to a low point shortly before your usual bedtime²2 Dijk, 2009, so after hours of yawning you may find yourself oddly bright in the evening. You might catch yourself wiping down the kitchen or picking up a book you'd given up on by lunchtime. All through that second wind, the pressure for deep sleep goes on building steadily².

You may be counting the hours you lost and wondering whether they'll ever come back. Your body does make up for them, in its own way, and the way it does so works in your favor. Your body sets the depth of your deep sleepdeep sleep The slowest, most settled stage of sleep, when it’s hardest to wake someone. Most of it comes in the first part of the night. mainly by how long you've been awake²2 Dijk, 2009, so every hour you're up today adds to the sleep pressuresleep pressure The body’s need for sleep, which builds the longer we stay awake and eases while we sleep. that will take you into deep sleep tonight. The tiredness you feel now is that pressure building. After sleep loss, the next night begins with deeper sleep than usual², and returns to its ordinary pattern later on.

A short night keeps more deep sleep than it feels as if it did. When healthy adults in a sleep lab were given only four hours in bed, they still got about sixty minutes of deep sleep¹1 Banks et al., 2010, against sixty-nine on a ten-hour night. Most of what their short night cut away was lighter sleep, and their minutes of deep sleep were kept almost whole.

When the same people had a run of five four-hour nights and then a long night to recover, they made it up through both deeper sleep and extra length¹, and nobody knows how much came from each. There isn't a good figure yet for how many of one night's lost hours come back. Counting the hours misses that a big part of the payback is depth.

If you had the time to sleep last night and it wouldn't come, you may be tempted to win the hours back this morning or tonight. If someone else's needs kept you up, what helps when the nights belong to someone else is different. In one British study that followed ordinary sleepers for a year, about a third had a bout of short-term insomnia⁷7 Ellis et al., 2012, and it often passed. What can turn it into a longer pattern⁷⁸8 Patel et al., 2018 is the way we respond: extra time in bed, frequent naps and worry about the next night. The first two you can decide about this morning. The worry is harder, because you can't simply choose not to have it. What helps is knowing what you'd do with the hours if it keeps you up, and Should I get up if I can’t sleep? goes into that.

A nap draws on that same store of pressure, especially late in the day. In one small study, an early-evening nap made people much slower to fall asleep that night²2 Dijk, 2009. If you need one, a short nap earlier in the afternoon takes less from tonight. In one study, young adults whose night had been cut to about five hours napped for ten minutes at 3pm and felt and performed better straight away¹⁰10 Brooks & Lack, 2006. A half-hour nap left them groggier at first. Ten minutes is well within the usual guide of around twenty minutes or less. The guide is loose, because how groggy a short nap leaves you depends on how short your night was and the time of day⁴¹¹4 Trotti, 201711 Hilditch et al., 2017. Are naps good for you? goes further into it.

If the bad nights have been running on for weeks, that's a different thing from one night, with its own help in What is CBT for insomnia, and what would it ask of me? So after a night of lying awake, the plan with the best grounds is also the plainest: up at your usual time, any nap short and early, and bed at your ordinary hour. Each part of it saves the day's pressure for tonight instead of spending it now.

By mid-morning you may find yourself reaching for another coffee, and the morning is when it takes least from tonight. Caffeine taken even six hours before bed can cut into that night's sleep¹²12 Drake et al., 2013. In one study, healthy sleepers at home took the caffeine in about four cups of brewed coffee six hours before bedtime. It cost them more than an hour of sleep. So you could have your cups early and let the afternoon go without, and How long does caffeine stay in your system? has the detail.

Light may help with the afternoon, too. In a small lab study, people who had slept five hours a night for two nights were less sleepy and quicker to react¹³13 Phipps-Nelson et al., 2003 when they sat in bright indoor light from noon to 5pm than when they sat in dim light. That's one small study, but a seat by a window after lunch, or a few minutes outside, asks little of you.

As attention is what slips most, it may help to go easy on work that needs it unbroken, like checking figures or measuring out a medicine dose. A dose is worth checking twice, however clear you feel. If a big decision is waiting, you could put it off where you can, or talk it through with someone.

Driving is where the brief lapses and the afternoon dip meet. Among drivers in real US crashes, those who'd slept about five hours in the day before had nearly twice the odds of causing their crash¹⁴14 Tefft, 2018 as those who'd slept seven to nine. In a driving simulator, researchers sat sleepy volunteers through a long, dull afternoon drive. Their sleepy incidents peaked in the mid-afternoon¹⁵15 Reyner & Horne, 1997. A coffee beforehand cut those incidents to about a third¹⁵ of what they were without caffeine. That's better, but a third is still a lot. In a second study, drivers who'd slept five hours tried cold air from the window and the radio turned up, and neither made any real difference¹⁶16 Reyner & Horne, 1998 to how they drifted. For your drive today, coffee lowers the danger without removing it, and the window and the radio do next to nothing.

If you feel drowsy, please don't drive. If you can, let someone else take the wheel, or wait a while before you set off. Some days there's no one else and the drive has to happen, and then it may help to keep away from the mid-afternoon if you have the choice. If drowsiness comes over you on the road, please pull over somewhere safe, have a coffee and a short nap there, and then drive on only as far as you need to. In the same simulator, coffee followed by a short nap cut incidents to under a tenth¹⁵, so on a drive you can't avoid, it's a way of lowering the risk.

If you were up with a baby, a sick child or someone you care for, there was no choosing, and much of what's said about protecting your sleep doesn't fit a night that belongs to someone else. The advice against sleeping in, napping and early nights to catch up is meant for someone who had the time to sleep and couldn't, and it isn't for you. Sleep is worth taking whenever it's offered, whether that's a short nap while the baby sleeps or an early night to get a stretch in before the first waking.

If you've had a baby, you know the nights are shorter. Among German parents, mothers in the first three months after a birth slept about an hour less a night than before pregnancy¹⁷17 Richter et al., 2019, and fathers about thirteen minutes less. How broken the nights are may matter as well. When researchers gave first-time mothers wrist monitors and a reaction test each morning, the mothers often got a near-normal total, but in pieces¹⁸18 McBean & Montgomery-Downs, 2013. Week by week, their lapses of attention in the morning rose¹⁸, even as more of their time in bed went on sleep. It's one early study, of new mothers only, but it suggests that broken nights wear on your attention even when the hours add up. So anything that adds unbroken stretches, whenever they come, may help most.

If there's someone to share the nights with, you could take turns, so that each of you has one longer stretch of unbroken sleep. That may give the body room to sleep more deeply, an idea that comes from how sleep pressure works and hasn't been well studied. Among the same mothers, those whose sleep fell in a steadier, earlier window had fewer lapses¹⁸, so steadier, earlier hours may be worth trying on the nights that allow it.

On a run of short nights, feeling all right is a weaker guide than usual, mostly when it comes to driving. When people in a lab were kept to six hours or less a night, their attention kept slipping¹⁹19 Van Dongen et al., 2003 while how sleepy they felt rose only a little¹⁹. They were allowed no naps, so their picture is a ceiling, and the naps you can sometimes snatch may make yours milder. On a morning when you need to drive, it may be safer to go by how the nights have been than by how you feel.

If you care for an adult, the research on carers' sleep is thin, though support aimed at it seemed to help a little²⁰20 Cooper et al., 2022, by carers' own account. For you too, any sleep the days and nights leave room for is worth having, and an unbroken stretch may do more for you than the same hours in pieces. If anyone can take a night, or even part of one, that stretch may be the thing to ask them for.

All day, the pressure for deep sleep has been building²2 Dijk, 2009. After sleep loss, the sleep that follows tends to begin more deeply than usual². If your night will be broken again by someone who needs you, any unbroken stretch it allows, even an early hour before the first waking, may do you the most good. If the night is yours, an ordinary bedtime and the lights low are all it asks. And if sleep is slow to arrive, nothing has been lost while you wait. Your body sets that pressure by how long you've been awake², and it goes on building through the waiting.