• A person's assessment of how they slept is linked to their well-being, regardless of what their sleep tracker said, new research found.
• This suggests that people could improve their mood and well-being by thinking more positively about their sleep, though more research is needed.
• Experts aren't yet sure why sleep tracker data isn't related to how a person feels the next day.
  

How a person thinks they slept may have a greater impact on their well-being the next day than what a sleep tracker says, according to a new study.

The research, published in Emotion on August 3, could indicate that subjective sleep experiences are more important when it comes to well-being than more objective data.

“When participants reported that they slept better than they normally did, they experienced more positive emotions and had a higher sense of life satisfaction the following day,” lead study author Anita Lenneis, PhD, a psychologist, and honorary research fellow at the University of Warwick, said in a press release.

However, sleep efficiency, determined by the sleep tracker, “was not associated with next day’s well-being at all,” she added.

The study took place in the U.K., and included data from 109 young adults. More research needs to be done to determine if the findings are generalizable to other age groups and populations, however, the study could indicate that feeling good about the sleep you got could improve well-being.

Here’s what experts had to say about why self-perception of sleep trumps what the sleep tracker says, and ways to improve sleep quality to boost your next-day mood.

Being Satisfied With Sleep Is Correlated with Improved Well-Being

Other studies have found links between people’s emotions and their sleep quality, but this study in particular aimed to examine how sleep devices and perception changed well-being for each person.

“They were basically asking—in this young, presumably sleep-healthy group—how well does [an] individual’s sleep variables, or their report of sleep satisfaction, predict how good one feels during the day?” Michael Perlis, PhD, director of the behavioral sleep medicine program at the University of Pennsylvania Perelman School of Medicine, told Health.

The study included 109 undergraduate participants ranging in age from 18 to 22. About 64% were female, and about half were from the U.K.

Each participant submitted sleep data for two weeks between October 2017 and March 2018. They also wore actigraphs, devices that measures people’s movement, to track their sleep.

The actigraph recorded the following sleep metrics:

• Sleep onset latency, or how long it took people to fall asleep
• Sleep duration, or how many hours of sleep people got
• Social jet lag, or differences in people’s social and biological clocks
• Sleep efficiency, or the percentage of time a person slept for after going to bed

Through an app, participants were then given daily surveys that they had 24 hours to complete, which asked them to log when they went to bed, the time it took them to fall asleep, when they woke up, and if they woke up on time. They also ranked their “sleep satisfaction” on a scale from one to four.

In addition, the study participants were asked to fill out more frequent “momentary surveys,” as well.

“At five random time points throughout the day, our participants also reported on their well-being. More specifically, they rated their mood, (e.g., how happy, enthusiastic, upset, and worried they felt) and how satisfied they were with their lives at that very moment,” senior study author Anu Realo, MSc, PhD, a professor of psychology at the University of Warwick, told Health in an email. 

Taking this data, researchers looked for associations between people’s sleep habits and their subjective well-being, or generally, how positive people felt and how satisfied they were with their lives.

“Our results showed that young adults’ sleep satisfaction, that is their subjective sleep quality, was most consistently linked with their well-being on the next day,” Realo said. “Curiously, the actigraphy-derived measure of sleep quality was not associated with next day’s well-being at all.”

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Disconnect Between Sleep Trackers and Self-Reports Still a Mystery

As for why a person’s perception of how they slept the night before is linked to well-being more so than trackers, there could be a few different explanations.

For one, people may feel positive and energized if they think they’ve slept well. Though it’s not specifically examined in the study, it’s possible that “how you feel in the morning influences how you feel throughout the day,” Lenneis told Health in an email.

This may ring true, regardless of whether a person actually got objectively restful sleep—previous research has shown that “placebo sleep,” or thinking you’re more well-rested than you really are, has still been linked to improved cognitive function over people who believe they slept poorly.

Another explanation is simply that the metric of sleep satisfaction may be able to better explain how a person actually slept, Perlis said.

“It’s an omnibus variable,” he added. “Lots of things go into whether you’re satisfied with your sleep.”

This could explain why this subjective variable was more closely tied to well-being—the general feeling a person has about how well they slept likely involves dozens of different factors, whereas the sleep tracker can only measure a few things that might have an effect on sleep quality.

“There is more that goes into sleep than just how long does it take you to fall asleep? How long were you asleep for? How much did you wake up? How efficient is your sleep?” Perlis said. “There’s more to it.”

This is especially true when connecting it to something else that’s subjective—namely, people’s well-being and life satisfaction.

“If you’re asking about subjective experience of the night, and you’re asking about subjective experience of the day, it’s not a shock that those things are best correlated,” Perlis added.

But for now, we can only speculate as to why there’s a dissonance between self-reported feelings about sleep and what trackers say.

This disconnect is “consistent with previous research,” Realo explained, but it’s not clear “whether people are bad judges of their sleep quality, or [whether] we need better and more accurate sleep measurement techniques.”

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Increasing Well-Being with Quality Sleep

The study has a smaller number of participants with an extremely limited age range. Because of this, the findings are not generalizable to the broader population, especially since “sleep patterns and quality tend to change as people age,” Realo said. Future research should examine whether this connection between subjective well-being and perception of sleep exists for different ages or other groups, the study authors wrote.

However, this link could have interesting applications in people’s lives, as people navigate ways to sleep and feel better.

“Your perception of sleep might be more important than what sleep trackers say about it when it comes to your well-being,” Lenneis said. “If someone thinks that they slept badly but a sleep tracker said that they did sleep more or better than they did, it might be useful for reappraising your sleep.”

It’s of course more likely that a person evaluates their sleep positively if they feel like they got enough sleep. Not doing so may not only worsen a person’s mood, but can also raise the risk of type 2 diabetes, stroke, poor mental health, and early death.

In order to improve sleep, people have to make sure they have the opportunity to sleep, the ability to sleep, and the correct amount of sleep that they need, Perlis explained.

He and his team have been developing a screening survey that people can take to get a better idea of their sleep health, and whether they might be experiencing any sleep disorders. The idea is that, if people aren’t feeling satisfied with their current sleep habits, they can take the report to a doctor to get any potential issues evaluated, he said.

People can also improve their sleep—and possibly, their well-being—by committing to simple strategies such as going to bed at consistent times throughout the week, avoiding electronic devices before bed, and making sure their bedroom is quiet, relaxing, and dark.

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