Why do I wake up at 3 a.m. every night?

(CNN) — Now wide awake from a once peaceful slumber, you roll over to check the clock and find it’s 3 a.m. That’s the same time you woke up last night. And the night before.

If that sounds familiar, it’s because nocturnal awakenings happen to a lot of people. Waking up several times throughout the night is a natural occurrence often due to sleep architecture, which are the stages of sleep that one cycles through every night.

These awakenings usually only last for anywhere from a few seconds up to a few minutes — if they happen too frequently in one night or there are disruptions to falling back asleep, that could be a problem. Here’s what experts say could help.

Why you might be waking up

Sleep architecture refers to the four stages of sleep people cycle through during the night in about 90 to 120-minute intervals, said Dr. Brandon Peters-Mathews, a neurologist with Virginia Mason Franciscan Health in Seattle.

The cycle begins with a light sleep that transitions into a deeper sleep, and then into the deepest sleep that occurs in the third stage, often referred to as “slow-wave sleep,” Peters-Mathews said. During the fourth stage, known as rapid eye movement (REM) sleep, brain activity picks up to levels that almost reach normal activity while awake — it’s after this stage when people often wake up naturally, he said, and once they fall back asleep the cycle begins again.

“Because we tend to go to bed at roughly the same time on a nightly basis, and these cycles are roughly the same length, we may wake at the same time in the night,” Peters-Mathews said. Most of these awakenings will be brief and forgettable, but “there might be one or two cycles into the night that we wake up and look at the clock and are aware of the time.”

Waking up several times throughout the night is typically not disruptive to one’s health, as long as falling back asleep occurs within about five to 10 minutes, said Dr. Michelle Drerup, director of the Behavioral Sleep Medicine Program at the Cleveland Clinic.

On the other hand, when people find themselves waking up multiple times within the hour, that could cause a sleep cycle to be fragmented and the individual might not get any deep sleep, Drerup said. These frequent awakenings could be a sign of sleep disorders such as sleep apnea or nocturia, she added.

When people naturally wake up in the night, they are more likely to remember it happening during the second half of the night. That’s when people typically have longer REM stage, light sleep, while the first half of the night has longer stages of deep sleep instead.

“People will say, ‘Oh, I sleep like really solidly for four hours. And then I feel like I have more waking. And that’s also very normal based on our sleep architecture,” Drerup said.

It’s often a person’s emotional response to the awakening that can pose challenges, Peters-Mathews said, and could result in someone developing secondary insomnia if their reaction triggers prolonged wakefulness.

“If somebody wakes in the night, and the first thing they do is look to their alarm clock, and see what time it is, and that’s something that makes them feel frustrated or upset or anxious as they anticipate the next day — it’s the reaction that’s problematic,” he said.

Night owl or early bird

A person’s circadian rhythm, or internal biological 24-hour clock, could also be at play, said neurologist Dr. Cathy Goldstein, a sleep medicine physician at the Michigan Medicine Sleep Disorders Centers.

Your circadian rhythm tells the body when it’s time to sleep and tends to line up with your past sleep-wake cycles and the exposure to light throughout the day. If this rhythm is thrown off, or the sleep-wake cycle changes a lot, the body is not going to have a great idea of when to have high-quality deep sleep, said Goldstein, who is also a professor of neurology at the University of Michigan in Ann Arbor.

“Circadian rhythm is our internal biological clock, it times when we’re awake, it times when we’re asleep — it times most of our physiological processes, so our body does what it needs to do at the right time of day,” Goldstein said.

Circadian rhythms and sleep architecture change with age, which might be why someone could feel like they received more deep sleep when they were younger. As people age, they tend to spend more time in light stages of sleep, she added.

These cycles are inherent and might also establish someone as a night owl or an early bird, Goldstein said, and could cause difficulty with keeping up with a work schedule that does not align with an individual’s biological cycle, resulting in daytime sleepiness.

Often, even though someone wakes up early for work, falling asleep at a time that allows them for enough sleep can be a challenge. What’s more, many night owls also tend to go to bed late on the weekend, which can result in drowsiness known as “social jetlag” and will weaken the circadian rhythm — possibly causing less deep sleep and resulting in more awakenings, Goldstein said. But there are ways to move around your internal clock.

What to do if you can’t fall back asleep

Falling asleep and waking up at the same time every day, as well as getting natural light exposure throughout the day and dimming artificial lights at night, will help strengthen your circadian amplitude — the peaks and troughs of the cycle — Goldstein said, resulting in more restful sleep.

It could also be helpful to take a very low dosage of melatonin, no more than half a milligram, a few hours before someone tends to naturally fall asleep, which could help to move the body clock earlier, she added.

The most important thing to do when waking up in the middle of the night is to resist looking at the clock, Peters-Mathews said. “If the alarm is not going off, it’s not time to wake up. It doesn’t matter what time it is. You get to roll over, get comfortable and go back to sleep.”

If you don’t fall back asleep within 15 minutes, it’s best to get out of bed to avoid developing an association with wakefulness with your bed, Drerup said. She recommends doing a quiet activity that will help one feel sleepy again, which could be meditation or listening to music.

“Our brains are highly associative, and they can get easily conditioned so that if we stay in bed for a long time, and we’re awake, our brains start to associate the bed with wakeful activities, like worrying and doing all kinds of things besides sleep, so getting out of bed breaks that association,” Drerup said.

It’s also important to ensure the awakenings are not happening from something external, such as disturbances from your sleep partner, Peters-Mathews said. “Optimizing the sleep environment is important. … It sometimes means locking pets out of the bedroom and optimizing noise, light and temperature within the bedroom environment.”

But if the awakening is naturally caused by your sleep architecture and does not affect how you function the next day, there is nothing to worry about, Goldstein said.