By Jamie Ducharme, Time.com

Have you ever slept a full eight hours but awakened feeling as tired as if you had pulled an all-nighter? If so, you may have experienced what’s known as unrefreshing sleep.

Unrefreshing sleep, also known as non-restorative sleep, is exactly what it sounds like: sleep that doesn’t recharge the body and brain enough to help you feel well-rested. People who experience it “feel just as tired as they were before they went to sleep,” says Thomas Roth, founder of the Sleep Disorders and Research Center at Henry Ford Health in Michigan.

Here’s what to know about unrefreshing sleep, and what to do if you experience it.

What is unrefreshing sleep, exactly?

People with insomnia struggle to fall or stay asleep and are often painfully aware of how long they’ve spent lying in bed wide awake. That’s not necessarily the case with unrefreshing sleep. Sufferers may wake up feeling fatigued even if they fell asleep quickly and didn’t get up at all during the night—in other words, they may be sleeping long enough, but the sleep isn’t doing its job.

“A lot of times people feel like, ‘It doesn’t matter how long I sleep. I wake up and feel like a truck ran over me,’” says Dr. Sonja Schuetz, a neurologist specializing in sleep medicine at University of Michigan Health.

What causes unrefreshing sleep?

Unrefreshing sleep can be a symptom of a larger medical problem, such as restless leg syndrome, fibromyalgia, myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS), or Long COVID. Some treatable sleep disorders, such as hypersomnia, sleep apnea, and narcolepsy, also result in excessive daytime fatigue, even if someone slept plenty the night before.

“If sleep is [chronically] unrefreshing, you need a medical workup” to rule out these and other conditions, says Dr. Lucinda Bateman, founder of the Bateman Horne Center in Utah, which is dedicated to improving care for people with ME/CFS, Long COVID, and fibromyalgia.

But some people experience unrefreshing sleep without a clear underlying medical cause. Researchers aren’t entirely sure why that happens—but at its core, the problem seems linked to inadequate deep, restorative rest, Schuetz says.

During an average night, someone will go through four to six sleep cycles, each one comprising four different stages of sleep. The deep sleep that helps the body and brain recover happens toward the end of each sleep cycle. “There’s a certain amount of deep sleep that is required for good sleep quality,” Schuetz says. People who experience unrefreshing sleep may, for whatever reason, not get enough, leaving them fatigued during the day even after hours of shut-eye.

Why? One possibility is that some people experience “micro-arousals” throughout the night, waking numerous times but so briefly that they don’t remember it by morning, says Roth, who has studied non-restorative sleep. (That’s well-known to happen in patients with sleep apnea, who may wake dozens of times per hour.) And sometimes, Roth says, brain waves typically seen while awake "intrude" upon deep sleep, potentially harming overall sleep quality.

Chronic stress, anxiety, pain, or nervous-system dysfunction can also degrade sleep quality, Bateman says. Lifestyle and environmental factors can make a big difference, too. Background noise and ambient light can lead to poorer sleep, Schuetz says, as can drinking even small amounts of caffeine and alcohol. 

What to do about unrefreshing sleep

Everyone has the occasional night of poor sleep, leading to a drowsy next day. But if you’re constantly struggling with non-restorative sleep, it’s worth taking a hard look at your habits and sleep hygiene.

First, make sure you’re actually getting enough sleep, Schuetz says. Some people think they need less than the recommended seven to nine hours per night, but are in reality walking around chronically sleep-deprived. “A lot of times, insufficient sleep feels like unrefreshing sleep,” Schuetz says. To test whether you’re well-rested, she suggests, skip setting your alarm on your day off and see how late you wake up without it. If you sleep in late, that's a signal that your body needs to catch up on rest because you’re not getting enough shut-eye normally.

Next, take a look at any medications you’re using. Sleeping pills and other types of prescription drugs, as well as over-the-counter remedies like melatonin, can have “hangover” effects that lead to morning grogginess, which can create or worsen the feeling of unrefreshing sleep, Bateman says. (Weed edibles, which some people use as sleep aids, can also result in morning grogginess—and potentially throw off sleep cycles in ways that make slumber less restorative, research suggests.) If you’re on a necessary medication that makes you feel fuzzy in the morning, ask your doctor if there’s a way to minimize side effects.

And, of course, it’s worth trying to implement the classic sleep advice you’ve probably heard a million times, but likely still don’t follow to a tee. Limit caffeine and alcohol consumption; stay off your phone close to bedtime; create a soothing bedtime routine and aim for consistent sleep and wake times; and try to sleep in a cool, dark, quiet room. Mindfulness and relaxation practices that minimize stress and anxiety also go a long way toward better sleep, Bateman adds.

If you’ve done all these things and still feel like your sleep isn’t restorative, to the point that it’s disrupting your daily life, it’s worth seeing a doctor. A physician can look for underlying medical causes—and, hopefully, help you land on a regimen that leaves you feeling rejuvenated in the morning.

Published in Time.com