Bad bedfellows

illustration of a woman in a bed, viewed from above; she is wearing a sleep tracking device and on the left side of her bed there are icons representing the data the device is collecting

You woke up with a pep in your step, feeling energetic and well rested. But wait: your sleep tracker says otherwise. Does the data change your plans for the day and how you'll approach bedtime that night? Are you now anxious when you'd been feeling calm?

The rise of sleep tracking devices — which monitor physiological factors related to sleep — has made this conundrum increasingly relevant. A 2023 survey by the American Academy of Sleep Medicine shows that more than one-third of Americans have used electronic sleep tracking devices.

Seven hours of sleep each night are generally adequate for an average adult, Harvard experts say. But many folks are fixated on getting a "perfect" eight hours after learning that sleep deprivation can raise the risks of an array of potentially serious health problems, including obesity, diabetes, and cardiovascular disease. The quest for better sleep may backfire, however, leading to anxiety and stress that can thwart restful slumber.

"We do need to lower the emotional temperature a bit and be rational about this," says Dr. John Winkelman, chief of the Sleep Disorders Clinical Research Program at Harvard-affiliated Massachusetts General Hospital.

"Many people still don't respect the importance of sleep, but using sleep trackers feeds into some people's anxieties," he says. "Anxiety and psychological arousal are the opposite of what we need when we sleep."

Influential data

Many types of devices are marketed to track sleep, ranging from watches and rings to smartphone apps and mattress monitors. Some measure whether you're asleep or not by recording aspects such as movement, heart rate, body temperature, and breathing patterns—all of which change at different sleep stages.

The data these devices generate can also hold a lot of sway over how people feel each day. A small 2018 study in the Journal of Sleep Research demonstrated this phenomenon. It involved 63 adults with insomnia who were given wrist-worn sleep trackers. In the morning, half of them received information telling them they'd slept poorly, while the others were told they'd slept well — regardless of their actual sleep quality. All reported on their mood and alertness several times over the course of the day.

The 32 participants who were told their sleep was poor reported lower alertness during the day and greater sleepiness in the evening compared to those given positive feedback. And people told they had restful sleep reported a significantly higher level of positive mood and alertness.

"In fact, there was no meaningful difference in sleep quality between the two groups," Dr. Winkelman says. "I'm a little bit addicted to my Fitbit, but I don't use it to inform how I feel during the day. I just like knowing the data and thinking about the relationship of the data to how I think I slept. But understand: those two things are far from synonymous."

Pluses and pitfalls

Using sleep trackers can present distinct pros and cons, Harvard experts say. Among the pros:

They can make you more aware of your sleep patterns.
They can offer affirmation if you're trying to form better sleep habits. "Trackers allow people to see if their bedtimes and wake times aren't stable, which they should be," Dr. Winkelman says. "Our sleep is really best when we're on a regular schedule."
They can identify a potential sleep disorder by spotlighting signs such as awakening many times during the night. "Some trackers offer information about your oxygen variability," Dr. Winkelman says. "They can be very helpful in identifying sleep-related breathing disorders, such as sleep apnea."

But the devices can also lead to an unhealthy preoccupation with sleep, which can fuel insomnia, Dr. Winkelman says. Here are some other downsides:

Interpreting and using the data can be confusing. For example, your tracker may tell you that you're apparently not sleeping very deeply, but you might not know how to change that.
Focusing on sleep data may lead some people to ignore how they actually feel after sleeping. "Can you wake up without an alarm clock? Make it through the day without feeling exhausted or drinking five cups of coffee?" asks Dr. Elizabeth Klerman, a professor of neurology at Massachusetts General Hospital and the Division of Sleep Medicine at Harvard Medical School. "To me, those are probably much more useful metrics."

A lack of accuracy

Sleep trackers are only as useful as the data they produce — which aren't always accurate. A small 2019 study in the journal Sensors compared several types of sleep trackers to the gold standard of sleep measurement, a sleep study called polysomnography. After comparing 27 nights of sleep study recordings in 19 participants ages 19 to 64 (66% women) with sleep tracker data from the same nights, researchers found the trackers lacking.

Specifically, the devices had difficulty detecting participants' wake periods, which hindered their ability to estimate total sleep time and sleep quality. However, the sleep trackers accurately detected the most basic sleep parameter — the actual amount of time participants spent in bed.

"They're not accurately reflecting how much sleep people are getting, or the depth of sleep or type," Dr. Klerman says. "I think they're more accurate now than they used to be. On the other hand, they haven't been tested on every type of person who wears them."

What color is your sleep noise?

It may seem paradoxical that a noisy environment could promote sleep. But some people prefer not to slumber in total silence — instead, they add background sound to the bedroom to sleep more soundly.

Recent years have seen a proliferation of sleep machines and apps that emit various audio frequencies that sound similar to static from an untuned radio or TV. Some people profess that listening to these monotonous sounds before or during sleep can help them drop off more easily and stay asleep longer, calming them and drowning out background noise like traffic or creaky pipes.

These sounds have colors assigned to them based on each noise's strength and frequency:

White noise is perhaps the best‑known of all noise colors and contains all audio frequencies. It can be intense and high-pitched, resembling a fan, air conditioner, or vacuum.

Pink noise is lower-pitched than white noise. It sounds like steady rain, wind blowing through trees, or waves on a beach.

Brown noise sounds more bass, like a rushing river, pounding surf, or strong winds.

Sleep-boosting measures

If you've found that anxiety surrounding sleep is keeping you from restful slumber, Harvard experts suggest seeking a special type of cognitive behavioral therapy, called CBTi, that's designed to improve insomnia.

"The cognitive part works on anxious thoughts, while the behavioral part actually decreases the amount of time you spend in bed so you're really sleepy when you get there," Dr. Winkelman says.

Here are some other tactics to improve your sleep:

Set consistent bed and wake times. You can use a tracker to help you do this or merely rely on the clock. But either way, the practice should prod you to wind down calmly before bed.

Don't check sleep data first thing in the morning. Start your day, decide how you feel, and then look at your sleep tracker.

Monitor substance use surrounding sleep. Pay attention to when you last used caffeine, alcohol, and tobacco, which can all affect sleep quality.

Consider your medication use. Ask your doctor if any prescriptions or supplements you take might make it harder to fall or stay asleep. Tweak the use of those medications if possible.

Stay alert for breathing issues. If your bed partner says you snore or gasp frequently while sleeping, tell your doctor. Ditto if you can't sleep lying down and need to sit up, which usually indicates breathing problems. "A tracker may not catch that," Dr. Klerman says. "That's really good evidence you should see a health professional."