Sleep Regularity More Important than Sleep Duration, Study Finds

Sleep Regularity More Important than Sleep Duration, Study Finds
30.12.2023
  • New research found that sleep regularity is more important than sleep duration.
  • Another study found that individuals who lacked a regular sleep schedule saw greater risk of cognitive decline.
  • Experts recommend people follow healthy sleep habits—getting sunlight first thing in the morning, exercising during the day, and maintaining a calm bedroom environment—to help form regular sleep patterns.

Regularity is more important than duration when it comes to sleep habits, a new study finds.

Not getting enough sleep has been linked to health issues like heart and kidney disease, hypertension, depression, and more. However, a regular sleep routine may even more profoundly impact health.

New research, published earlier this year in Sleep, compared how consistent people were with their bedtime and wake-up schedules to how long people slept during the night.

The study authors found that sleep regularity better predicted a person’s mortality risk than sleep duration.

Participants with the most consistent sleep schedules had a lower risk of all-cause mortality, in addition to mortality from cancer and cardiometabolic disease.

“Making your wake time consistent across all days seems to be the underlying message,” said Sara Nowakowski, PhD, associate professor of medicine and behavioral sleep medicine provider at the Baylor College of Medicine.

Here’s why sleep regularity is important for well-being and what people can do to improve the consistency of their sleep schedules.

Regularity Is Something to Consider for Sleep Health

The Sleep study focused on data from approximately 61,000 participants from the U.K. Biobank cohort. The participants were on average about 63 years old, just over half were women, and over 97% were white.

For one week, the researchers tracked their activity via an actigraph, which is similar to a smartwatch, explained Nowakowski.

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This device allowed the researchers to estimate when each person went to sleep and woke up each day, taking into account naps, fragmented sleep, and periods when people were awake in the middle of the night.

This allowed insight into people’s “day-to-day variability” of sleep, Nowakowski said.

Actigraphy data was used to determine each person’s “Sleep Regularity Index,” which described how consistent a person’s sleep was on a scale from zero to 100, the latter representing perfectly regular sleep.

Comparing mortality data for the participants, researchers found that people who scored at least 71.6 on the Sleep Regularity Index had between a 20% and 48% lower risk of all-cause mortality. This group also had between a 16% and 39% lowered risk of death from cancer, and a 22% to 57% lowered risk of death from cardiometabolic diseases.

While longer sleep durations were also associated with a lower mortality risk, sleep regularity was an even better indicator of mortality risk.

This isn’t the only recent study to stress the importance of regular sleep habits.

JAMA Network Open study published earlier this month tracked the self-reported sleep of older adults. Researchers found that frequently sleeping for fewer hours and having inconsistent sleep duration were both associated with cognitive decline.

It’s important to emphasize that both new studies found an association—not causation—between regular sleep and improved health outcomes, Richard Castriotta, MD, pulmonary critical care and sleep medicine specialist with Keck Medicine at the University of Southern California.

So, it’s not clear if irregular sleep is causing a higher mortality risk or cognitive decline, or whether these health issues are worsening people’s sleep, he said.

But overall, both studies point to the idea that sleep consistency can greatly influence people’s health.

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“The outcomes are different—one’s mortality and one’s cognitive functioning—but they’re both telling you that regularity of sleep patterns is very important,” said Nowakowski.

Why Consistency Matters So Much

Emerging research is connecting sleep to circadian rhythms, Nowakowski explained.

“Everything in our body operates on this 24-hour clock—our appetite, our hormones, our peak performance, our sleep,” she said.

Circadian rhythms are influenced by light and dark, as well as by genetics and routines. When a person’s sleep cycles are out of sync with their environment and internal body clock, that can lead to health issues.

Castriotti explained that having jet lag after a long flight is a good way to illustrate it.

“It’s not just that you feel tired—your digestive tract isn’t working right, your muscles are all aching, everything is out of whack, because some parts of your body are acting in one timezone and others are acting in another,” he said.

Though it’s not typically to the same degree as jet lag, many people have a long-term disrupted sleep-wake cycle, where they’re awake when their body wants to go to sleep (or vice versa).

Prior research has found that this disruption of the circadian rhythm—particularly in people who do shift work—can lead to autoimmune disorders.

Also, Castriotta explained that blood pressure typically goes down at night when a person sleeps—if that’s consistently disrupted, people may see a higher risk of heart attack, stroke, kidney disease, and diabetes.

There’s also a relationship between disrupted sleep, high cortisol levels, and strain on the heart and brain, he added.

More research on circadian rhythms and sleep is necessary, but there’s no denying that going to bed and waking up at the same time every day seems to benefit overall health.

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How to Prioritize a Regular Sleep Routine

Coming up with a consistent sleep-wake schedule is the first thing experts recommend if people want to improve their sleep.

“Have an average, set sleep time,” said Castriotta. “No matter what time you go to bed, no matter whether it’s a weekend or weekday, and whether you have work or school, get up at the same time every day.”

On top of this set wake-up time, people should plan to get about seven or eight hours of sleep and set their schedule accordingly.

To make that easier, people should take some time beforehand to “cool down,” Castriotta said.

“Avoid the TV and cell phone and computer and blue light,” he said. A warm bath or shower before bed and avoiding any stimulants (like caffeine) can also be helpful.

Still, Nowakowski explained there’s not a perfect way to ensure a regular sleep routine.

“You’re busy [during] the week, you have to get up for your kids or work, and you’re just cutting it short,” she said. “I think you can make up a little bit [of sleep].”

Ideally, if someone wanted or needed to sleep in, they’d get up no more than an hour later than usual, she said.

Bedtime and wake-up time aside, getting sunlight in the morning is another way people can improve their sleep regularity, Nowakowski said.

Other helpful sleep hygiene habits include exercising during the day and keeping the bedroom dark, cool, and quiet.

“If you want to optimize your sleep and your sleep health,…realize and recognize that it’s good to get it consistent across all days—both the schedule, the timing of it, and how much you’re getting,” Nowakowski said.

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