What I Learned From Tracking My Sleep With an Apple Watch

After having the same Apple Watch for six years, I was recently moved to upgrade to a newer model—partly because newer versions simply have more features, partly because I am curious about my bodily processes, and also because I am an impulsive spender convinced that every new purchase will be the one that brings me to the precipice of pure wellness. In the week that I’ve had my fancy new doodad, I have not become a paragon of perfect health, but I have gained some insights into my activity levels and, importantly, my sleeping habits. I am a firm believer in over-preparing for luxurious sleep sessions, so I wanted to see if the data my watched gleaned from my body overnight backed up my insistence that better sleep is possible through investments in things like fancy pillow sprays and silky sheets.

What the Apple Watch measures overnight

The Apple Watches you get nowadays come preloaded with a Sleep app that will estimate the amount of time you spend in REM, core sleep, and deep sleep, provided you wear your device when you hop in the sheets. It’s important to know that you have to pre-define your sleep schedule within the app for this to work; it doesn’t necessarily magically detect that you’ve gone to bed. I set mine to be from 1 a.m. to 8:30 a.m. after some internal debate about whether I wanted to lie to it (which would be useless) or be honest about what kind of person I am and when I actually go to bed. To get data from the watch, you also need to give it at least four hours of sleep to work with per night. You can set separate schedules for weekdays, weekends, or any other days you have special requirements or schedules.

When you wake up every day, the watch will figure out that you’re up and at ‘em and halt sleep monitoring. Then, you can see a little chart that estimates how long you were in each sleep phase. The sleep phases are defined like this: 

• REM is the phase where you’re dreaming most
• Deep sleep is a restorative phase that is good for your brain and body
• Core sleep is how Apple refers to lighter sleep that doesn’t fall into either of those categories

You get a chart that shows you how long you were in all three the previous night and can see trends for the previous two weeks. My average sleep time since acquiring the watch is six hours and 26 minutes. This is sad, but there is room to improve.

What you can learn from your Apple Watch sleep data

My watch claims that last night, I slept for six hours and eight minutes, with REM sleep comprising an hour and 21 of those, deep sleep making up just 45 minutes, and core sleep coming in at four hours and two minutes. That tracks with how it’s been all week: I’m mostly in core sleep and dabble a little bit in REM and deep. The watch, of course, isn’t measuring my brain’s electrical activity or any of the super science-y elements that would give medical-grade insight, but it does monitor breathing and movement. 

The most important insight you really gain from wearing this thing to bed is how long you’re actually sleeping. For me, gamification is one of the only ways I can tolerate the boring parts of adult life, so challenging myself to stop emailing, scrolling, reading, or doing who-knows-what-else I do instead of going to sleep in an effort to maximize my total sleep time data is fun. The amount of sleep you get is important, whereas the phases are more like bonus information (unless you really have a sleep issue that you’re trying to hone in on, which you should work on with a professional). 

Things to note before tracking sleep with Apple Watch

When I woke up this morning, I learned my Apple Watch had died at some point in the night. Nevertheless, my sleep data claims that I woke up at 8:32, though I don’t know how it got that information if it was dead when I did that. Whether it died at 8:31 or some other time, I’m regarding today’s new data with some skepticism. 

To prevent this from happening to you, be smart about your charging. Charge the watch while you’re in the shower or during your wind-down time before bed, times when you don’t need your activity tracked or to be responding to emails at all and, thus, the watch is largely useless. You can also use the watch’s Sleep app to set up reminders for charging, so if your pre-defined wind-down and sleep schedule coincides with a time when the device is under 30% battery, it will remind you to stick it on the charger.

Helpful tools to make sleep tracking on Apple Watch work

There are a few ways you can maximize the efficiency of the sleep tracking and necessary charging. Consider these items:

• Try a portable Apple Watch charger so you can charge it in the car, while you shower after the gym, or wherever and whenever else that will make it possible for the thing to be powered up overnight. This one from Newdery (US$7.59) is a simple charger on a USB stick, so you can use it in the car or plug it into any computer or wall adapter. Or, you can use the kind that you pre-charge at home and take on the go, like this one from Huoto (US$15.99), which has a convenient keychain.
• The watch needs to be snug to collect your data overnight, so if you wear it looser in the daytime and only care about seeing notifications on it, consider adjustable bands that you can tighten up before bed. Here’s a pack of 10 in a variety of colors for US$14.19.
• Grab a sleek three-in-one charger (US$19.93) to keep next to your bed for your phone, Airpods, and (when necessary) Apple Watch. God forbid you get that lower-than-30%-charge notification before tucking in, you can just slip the watch on the stand with the rest of your devices.