You go to bed exhausted. A few hours later you're awake, moving through tomorrow's responsibilities and working out a problem you fully intended to leave until morning. Then morning comes. You get dressed, show up, and do what needs to be done. Your work is still good, so when you think about how you're handling the pressure, you tell yourself you're managing.

Changes in your sleep can be an early indication that stress is affecting you, even while your performance stays steady. You may notice the strain at night before it becomes obvious in your work.

Why good work can hide the strain

When you're accustomed to being capable and dependable, getting the work done can become your main way of deciding whether you're okay. During a demanding stretch, you find ways to keep doing it. You concentrate harder, give yourself extra time, or rely on skills you've practiced for years. So you can still be doing good work even when it takes more out of you than usual.

Your sleep gives you another clue. Think of it as a check engine light. It doesn't tell you exactly what's going on, but it's a reason to take a closer look.

And the trouble isn't always waking in the middle of the night. You can feel completely exhausted all evening, and then, by the time you get in bed and lie back, you're fully awake. Stress can leave you too alert to sleep, even when you're worn out.

Sleep reactivity: how easily stress disrupts your sleep

There's a reason this happens more easily to some people than others. It's called sleep reactivity, and it means how easily stress disrupts your sleep. Some people go through a demanding stretch and their sleep barely changes. For others, it becomes harder to fall asleep, or they wake during the night and have trouble getting back to sleep.

Sleep researchers treat this as a fairly stable trait. It runs in families, and studies that follow good sleepers over time have found that those with high sleep reactivity are more likely to develop insomnia later, particularly after a stressful period.

To see whether this describes you, think about what usually happens to your sleep when something important is coming up.

Maybe you have a meeting tomorrow that you've prepared for. You know what you're going to say, and you're not expecting it to go badly. But in bed you're still going over it, and it takes much longer than usual to fall asleep.

Or you have a difficult conversation in the afternoon. You work it out, finish your day, and watch a couple of episodes of a show. By bedtime you feel fine. You're not even thinking about the conversation anymore. Then you lie there for an hour, unable to fall asleep.

You may remember a similar pattern from earlier in your life, like trouble sleeping before exams or while waiting for an important decision. One bad night doesn't tell you anything. What matters is a tendency you've noticed across different situations.

You can have this tendency even if you usually sleep well. You might sleep fine for weeks, then hit a demanding period and suddenly have trouble. The sensitivity may not be obvious until something challenges your sleep.

This is also specifically about how your sleep responds to stress. It doesn't mean you feel anxious all day or react strongly to everything. You don't have to feel panicked or overwhelmed for stress to affect your sleep. You may simply feel focused, responsible, and very busy.

Why comparing yourself with a coworker misleads you

Say you and a coworker are working toward the same deadline. You're putting in similar hours, and you're both doing good work. They mention that they went home and slept through the night. Meanwhile, you were awake at three, thinking about a problem with the project.

It's easy to hear that and think, "Why can't I handle this as well as they can?" But you don't know that they're handling it better. One possible difference is that their sleep is less sensitive to stress. They may be just as concerned about the deadline without having the same trouble sleeping.

Their ability to sleep doesn't tell you how much pressure you should be able to tolerate. If your sleep has changed, that's worth paying attention to, even if the person working beside you seems fine.

When worry about sleep joins in

Sleep reactivity and worrying are not the same thing, but they overlap. Repeatedly going over a problem in your mind makes sleep harder, particularly when your sleep is already sensitive to stress.

Imagine you wake up and remember something you need to do tomorrow. You start working through it. Then you look at the clock and realize how long you've been awake. Now you're thinking about the project and wondering how you'll get through tomorrow on so little sleep. After a few nights like that, you may start worrying about sleep before you even get into bed, and anticipating another bad night can make it harder to settle.

So now there's worry about sleep on top of whatever was keeping you up in the first place.

Look at what changed in your workday

Think back to when the sleep trouble began. Were you taking on more responsibility? Had you started catching up on work at night because you couldn't get enough uninterrupted time during the day?

Maybe you check tomorrow's schedule before bed. Then you open a document, notice something that needs fixing, and start making changes. What was supposed to be a quick look becomes another half hour of work.

If that's happening, one adjustment to try is moving that review earlier. Before you finish work, make a brief note of what still needs attention and when you'll return to it. That gives you a place to pick up tomorrow without another round of problem-solving just before bed.

The idea is to give yourself some time to settle after work. It isn't a guarantee that you'll sleep well that night, so you don't need to get into bed and start checking whether it worked.

And if working until bedtime is the only way you can get everything done, take a look at why. Is there more work than can reasonably fit into the day? Are interruptions making it hard to finish things? It could be some of both. Evening work can feel easier because you finally have uninterrupted time. But if that's become your regular way of keeping up, it's worth looking at what would need to change during the day, especially if you've noticed your sleep is worse when you work late.

When to get an evaluation

Not every sleep change is caused by work stress. Medications, alcohol, pain, hormonal changes, and other conditions can all affect sleep. If the problem continues or affects how you function during the day, talk with a healthcare professional. Loud snoring or waking up gasping also deserves an evaluation.

If worrying about sleep has become part of the problem, you can get help with that too. For chronic insomnia, cognitive behavioral therapy for insomnia, or CBT-I, is a recommended first-line treatment. It addresses the habits and thoughts that keep insomnia going, including worry about sleep itself. You don't have to resolve every problem at work before getting help with your sleep.

If you've been judging how you're doing mainly by whether your work is getting done, include what's happening at night. You don't want to wait until your work starts slipping to take note of your sleep.