Some gadgets throw a lot of sleep-related numbers around, but they’re not all equally helpful
That is certainly a lot of information. And it explains, at least in part, why I spent the next morning in a mental fog. As it turned out, however, the ensuing days of agonizing over some of these numbers might not have been as helpful as I thought.
According to the Centers for Disease Control and Prevention, people who routinely sleep less than seven hours a night are more likely to report conditions such as heart disease, diabetes and depression. A recent study from the University of Galway in Ireland suggests that people with recurrent sleep problems are more likely to have a stroke at some point in their lives.
It’s no wonder, then, that wearable devices — like those worn by about 20 percent of American adults — are spewing out sleep-related metrics designed to help us make sense of our time out of consciousness. The catch? Sometimes these numbers are presented without much context, which can make it difficult to understand how valuable they really are. And other numbers, like the time you spend in restful “deep sleep,” are in some ways just educated guesses.
That’s because some of these wearables, despite their sophistication, can’t accurately measure what our brains are doing. Instead, they do their best to gauge where we are on our nightly sleep journeys by tracking and interpreting the kind of data a watch or ring can collect, such as: B. Your heart rate and movement in bed.
“This is a proxy for sleep, not sleep as traditionally defined,” said Cathy Goldstein, sleep researcher and associate professor of neurology at the University of Michigan.
None of this means you shouldn’t try to use your wearable technology to better understand how you sleep. Goldstein says these types of gadgets can be really helpful because “otherwise we don’t have a way to track sleep for days over time.” The trick? Pay attention to the right data types. To help you, here’s our guide to the sleep-related metrics your wearable tech might be giving you and how seriously you should take them.
In theory, keeping track of things without a smartwatch or fancy ring is easy: write down when you went to bed and when you woke up, and then do a little math. But where wearables really come in handy is in getting a complete picture of your time in bed.
“Nearly all commercial trackers are now really good at telling you what time you went to bed, what time you woke up, how much sleep you got, and how awake you were,” said Joshua Hagen, director of the Human Performance Collaborative at Ohio State University.
Ideally, he says, you should aim to actually get between seven and nine hours of sleep a night — a very different thing than spending seven to nine hours in bed trying to nod off. If you’re not reaching that watermark like many of us, viewing these numbers on your smartphone can help you realize that your sleeping habits need correction.
“It’s like tracking your calories,” says Goldstein. “That doesn’t change anything, but you can see the problem.”
The judgment: This is the most immediately helpful number to look out for.
time in different sleep stages
“The things I warn my patients not to get excited about is specific times they spend in REM sleep or deep sleep,” Goldstein said.
When professionals conduct studies to properly examine a person’s sleep quality, they rely on sensors that directly monitor brain activity, eye movements, chin and leg muscle movement, and more, she says. Only after researchers have collected all of these readings over an entire night do they go back and determine how long someone spent in each stage of sleep, for example.
Today, the most popular portable devices on the market track only a few of these signals. And none of them can guess what’s going on in your brain as precisely as the electrodes that would be taped to your scalp during a sleep study
“These are states that are defined by their EEG constructs,” she said, referring to the way sleep stages appear in electroencephalogram readings. “We just can’t expect (wearables) to measure the same thing.”
Also, it’s possible to read a little too much into some of these sleep stage numbers. According to Goldstein, researchers often don’t measure the time they spend in REM or deep sleep for more than a few days at a time, so they “don’t really know the relevance of the changes.”
Additionally, Ohio-based Hagen says there isn’t much definitive information out there on how to increase your deep sleep time. So it’s not worth worrying about that number.
“There’s not much you can do about that,” he said. “Your body gets what it needs.”
The judgment: Take these numbers with caution.
If your heart rate is 60 bpm, it’s not beating exactly once a second – there are micro-scale variations between these lubs and dubs. Collectively, these small deviations make up your heart rate variability, which Hagen considers a “global stress indicator” measured in milliseconds. And perhaps paradoxically, the higher your HRV, the better.
“If you’re very emotionally stressed, it’s very likely that you have low heart rate variability,” he said. “If you are sick, you could also have a low HRV. When you are rested and relaxed and all is well in life, you most likely have a higher HRV compared to your norm.”
Data on the tiniest fluctuations in your heart sounds pretty esoteric, and it’s true that you could quite easily get by without worrying about it. But Goldstein of the University of Michigan says this number can be useful for getting a sense of the toll some of the things you do in your daily life are taking on the quality of your recovery.
“If you’ve been drinking or eating certain foods, you may experience changes in your heart rate variability,” she said.
These HRV dips at night can help you figure out habits and practices that you should avoid during the day. And by checking your HRV during the day, you can also better understand how restful – or not – last night was.
The judgment: You probably don’t need to watch it all the time, but it can be enlightening.
Wearables like smartwatches and rings have become surprisingly good at measuring our breathing. But do most people really need to know how many times per minute they breathe while they sleep?
That depends on how much context you have.
“For the average consumer, looking at your breathing rate every day is probably not very meaningful,” says Hagen. But keeping track of that number and how it’s changing over time could provide important insights into the quality of your sleep.
While sleeping, most people tend to hover between 12 and 20 breaths per minute, and changes in this breathing rate can indicate serious problems. (For example, a consistently low RPM while sleeping could be a sign of sleep apnea.) But Hagen says the main thing is to keep your eyes peeled for consistent deviations from your norm — whatever that might be.
“Everyone’s numbers will be specific to them,” he said. “The more understanding you have, the more actionable that data could be.”
The judgment: It’s worth keeping an eye on over time, but comparing it to others might not be helpful.
Keeping track of the right sleep stats can help you understand why you’re feeling this way in the morning, but not all wearables are created equal. Here are the gadgets I’ve personally been using lately to help me track my time away from the waking world.
Do you have a sleep-focused wearable you want us to try? Let us know by sending a message to the Help Desk.
The all-purpose wearable: Apple Watch
If you’re one of the many people who use an iPhone, an Apple Watch can quickly provide some sleep data that you might find helpful.
Of all the models the company sells, the Apple Watch Ultra offers by far the best battery life – which is why I’m using one now – but other than that, it’s honestly overkill unless you’re a serious athlete. Thankfully, you don’t need the latest or most expensive model; Even older models dutifully track sleep duration and heart rate variability.
My biggest criticism? Apple’s Health app is pretty good at putting some of this sleep data into context, but to see all the stats we’ve discussed you have to jump back and forth between different sections of the app, which can get a little annoying.
The more subtle variant: Oura Ring Gen 3
I got some of the most immediately useful sleep insights from the latest Oura Ring ($299 plus $5.99/month subscription), which packs a suite of sensors into a sleek ring design. However, it’s a bit chunkier than many other rings I’ve worn over the years.
The accompanying app is among the best I’ve seen presenting the data it collects, and I really enjoy how unobtrusive the ring itself is, but not everyone is going to love the idea of paying monthly to use a gadget that does he’s already spent hundreds of dollars on it, even if the first six months of service are free.
Another discreet option: WHOOP 4.0
A number of readers wrote to the Help Desk asking me to try the WHOOP, a nondescript fitness band to wear around your wrist or arm. I’m glad they did – it takes an intriguing approach to tracking your movement that focuses on measuring the amount of stress you put on your body and how well you recover from it.
Its sleep-tracking tools offer many of the same measurements as other devices, although the WHOOP app thankfully points to specific types of data – such as: B. how often you wake up – more detailed. It also offers suggestions for how much sleep to aim for in a night based on how hard you’ve trained your body that day.
However, the WHOOP experience takes a lot of getting used to. For one, you’re not buying the band outright — instead, you’re paying a monthly fee for continued access to the service and getting the wearable “for free.” And unlike other devices that you typically plug in and charge, you have to charge a separate “backpack” battery that you attach to the WHOOP band when it needs to be charged.