Can Sleeping in 90-Minute Increments Really Help You Feel More Alert?

Fact checked by Nick BlackmerFact checked by Nick Blackmer

• On TikTok, people are touting the benefits of timing sleep so that you wake up at the end of a sleep cycle, which is about 90 minutes.

• The idea is to avoid grogginess by sleeping for a full, uninterrupted cycle.

• While experts say that it's ideal to wake up at the end of a sleep cycle, they don't recommend placing too much focus on sleep cycles when napping or getting your nightly shuteye.

From CBD to weighted blankets to alarm clocks that wake you up calmly, there’s always a new hack for sleeping your best. The latest sleep trend capturing the attention of many on TikTok is timing your sleep so you don’t wake up in the middle of a sleep cycle.

A sleep cycle is roughly 90 minutes long and repeats throughout the night. On TikTok, many people are touting the benefits of taking a 90-minute nap; others suggest calculating your bedtime and morning wake-up so that you arise at the conclusion of a 90-minute cycle.

“The idea is that waking up at the end of a cycle might leave you feeling more refreshed,” Shelby Harris, PsyD, DBSM, a licensed clinical psychologist and director of sleep health at Sleepopolis, told Health.

While it sounds like something worth trying, especially when you’re struggling to sleep well, does snoozing in 90-minute increments really help you get better sleep? Here, sleep experts explain the science behind the trend and whether aligning your shuteye with your sleep cycle is beneficial.

What Is a Sleep Cycle?

To understand why TikTokers suggest aligning your sleep with a complete sleep cycle, it helps to know how a sleep cycle works.

A sleep cycle consists of four stages: three states of non-rapid eye movement (NREM) and one of rapid eye movement (REM).

The first two stages of NREM, which last for a collective 15 to 30 minutes, is when brain activity gradually slows. Body temperature also reduces, muscles relax, and breathing and heart rate decelerates.

Then you enter the next phase, also known as deep sleep, when your body activity slows further and cerebral blood flow, the amount of blood supplied to the brain, drops. During this time, your body recovers, your immune system strengthens, and your body builds bone and muscle. This stage typically lasts 20 to 40 minutes and becomes shorter as you continue sleeping.

The final stage is REM. During this phase, your heart rate, breathing, cerebral blood flow, and brain activity start to pick up, and you dream most vividly. However, most of your body—except for your eyes and the muscles controlling breathing—remains paralyzed. You spend about 25% of your sleep in REM, and the stages get longer as the night progresses.

Does Waking Up at the End of a Sleep Cycle Have Benefits?

Experts said there’s some truth to the idea that waking up at the end of a sleep cycle, after a complete REM stage, can make you feel more alert.

During deep sleep, your cerebral blood flow decreases, “which is why it is particularly disruptive to awaken during this stage of sleep,” Daniel Gartenberg, PhD, founder of SleepSpace and a sleep health advisor at CPAP.com, told Health.

When you wake up from deep sleep, your brain experiences something called “sleep inertia,” which typically makes you feel groggy for about 20 minutes.

But “if you are very sleep deprived or have poor sleep quality, this groggy feeling might last longer, closer to 60 to 90 minutes,” Gartneberg said. “The reason for this is that your brain literally needs time to ramp up in the morning and get the blood flowing back to it.”

Should You Time Your Wake-Ups to Your Sleep Cycle?

Although waking up at the end of a sleep cycle may help you feel refreshed, experts interviewed said they don’t recommend placing too much emphasis on your sleep cycle when it’s time to get some rest.

For one, trying to time your sleep—whether at night or for a nap—to align with your sleep cycle can simply be too challenging. Your sleep patterns will differ from day to day, and not everyone cycles through the stages in roughly 90 minutes.

“While it is true that generally, we have sleep cycles that go in the pattern from light sleep, deep sleep, light sleep, to REM, and it takes people 90 minutes roughly to go through these cycles, the cycles can vary immensely between people,” Gartenberg said.

Focusing too much on timing your sleep can fuel anxiety, according to Harris. Being anxious “could negatively impact the quality of your sleep,” she said. “Trying to time sleep cycles perfectly isn’t always realistic.”

What Do Experts Recommend for Optimal Sleep?

When it comes to optimal sleep, Harris said what’s more important is not when you wake up but how much you sleep overall.

Regarding naps, Harris said to stick to around 20 minutes before 2 pm. That’s “usually best to avoid grogginess or trouble falling asleep later at bedtime,” she explained.

As for overnight sleep, most adults need 7 to 9 hours per night, she said. But Gartenberg stressed that individual sleep needs vary by person.

“Someone who is much healthier than another person may not need as much sleep as the person who isn’t healthy,” Gartenberg said. “It can also come down to personal preferences and what that individual feels works best for themselves and their body.”

It’s in your best interest to try to develop “a consistent sleep schedule…by falling asleep at the same time and waking up at the same time each day,” Gartenberg added.

Once you’ve laid that foundation, that’s when it’s better to start experimenting with your wake-up routine, he said. “You can start playing with different wake-up times and using a sleep window to determine if you do better at something more like 8 hours and 20 minutes than 8 hours and 25 minutes, which could be possible.”

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