Do fitness wearables track sleep effectively?

A good night's sleep can help you feel rested and recharged, while poor sleep or sleep deprivation can hit your sense of well-being and cognitive functioning and even lead to health issues in the long run. For too long, however, people have ignored sleep issues, blaming these on stress or anxiety. Tracking your sleep can be particularly important, though, if you suffer from sleep disorders such as sleep apnea.

Sleep apnea is a condition in which breathing repeatedly stops and starts during sleep. The most common is obstructive sleep apnea, or OSA, in which breathing can cease for more than 10 seconds—in some cases, as long as 100-120 seconds—repeatedly. The death, earlier this year, of veteran music composer Bappi Lahiri focused attention on this disorder.

This is where fitness wearables can help. As someone who suffers from OSA, I have been using these (Fitbit Sense, at the moment) to track my sleep patterns. I can also monitor improvement, if any, if I change a pillow or use a sleeping aid. Of course, you must consult a doctor if you think you have a problem; fitness wearables are not a substitute.

While the older fitness trackers used to monitor wrist movement to track sleep, the recent generation also monitors heart rate and factors like body temperature and snoring. The more advanced ones even pack in an SpO2 sensor to track blood oxygen levels. The trackers monitor duration and quality of sleep as well as sleep stages, reporting the phases in which you were awake, tossing and turning.

During a typical night, we cycle through various stages. Stage one is a state of extremely light sleep. In stage two, our brain waves begin to slow down. In stages three and four, referred to as deep sleep, our bodies grow and repair themselves. The final stage is called rapid eye movement (REM). During this, our brains become more active, and dreams occur. The cycle repeats every 90-110 minutes. Missing out on any stage is a sign of poor sleep.

Since looking at and dissecting all the data can be overwhelming, fitness wearables and their companion apps distill it into some meaningful insights and an easy to follow "sleep score". Earlier this year, Fitbit went even further, introducing a Sleep Profile that offers a longitudinal analysis of sleep patterns—essentially, over a period of time. Since sleep can vary significantly from night to night, it is a good idea to analyze sleep data over a longer period to find out, for instance, the time spent in light, deep and REM sleep, plus time awake, as well as how your sleep is related to activity, mood, and more.

A sleep profile or a long period of evaluation via sleep trackers offers an edge over a traditional sleep study, since it's both difficult and expensive to have sleep specialists at home over too many days.

This is where fitness wearables can help.  As someone who suffers from OSA, I have been using these (Fitbit Sense, at the moment) to track my sleep patterns.

This is where fitness wearables can help. As someone who suffers from OSA, I have been using these (Fitbit Sense, at the moment) to track my sleep patterns.

How accurate is it?

My ENT doctor concedes that a credible fitness tracker can accurately detect snoring and monitor restless sleep patterns. But—and that's a but echoed by most experts—sleep trackers are not diagnostic. Senior neurologist and sleep specialist Manvir Bhatia, director of the Neurology Sleep Center in Delhi, believes that people who snore and have excessive daytime sleepiness should undergo tests for OSA. An estimated 80-90% of adults with OSA remain undiagnosed, she adds.

Moreover, since they do not measure sleep directly and rely primarily on movement and heart rate for assessment, fitness trackers are of limited use. They measure inactivity as a surrogate for estimating sleep and one can fool a tracker by lying quietly while awake. So, such wearables often underperform in insomniacs.

Still, fitness trackers do have their uses. Sleep tracking raises awareness and offers early warning signs of a disorder. My family physician asserts that problematic sleep patterns can also be indicative of larger health problems. How frequently has a doctor asked you: “Do you sleep well?”

A recent study published in the US National Sleep Foundation's Sleep Health journal, conducted for the performance evaluation of a wrist-worn reflectance pulse oximeter, concluded that Samsung's Galaxy Watch 4 could potentially help measure OSA. It found that wrist-worn trackers embedded with reflectance PPG (photoplethysmography) sensors were accurate in continuously measuring oxygen levels, enabling researchers to screen for OSA.

Fitbit sleep score on the iOS app.

Fitbit sleep score on the iOS app.

What are my options?

Before you indulge in sleep tracking on your fitness tracker, or buy a new one for the same, be mindful of not getting fixated on sleep data. A 2017 study published in the Journal of Clinical Sleep Medicine, highlighted a downside of obsessive sleep tracking dubbed 'orthosomnia'. The condition where people obsessively pursue optimal sleep based on insights derived from sleep tracking can cause stress and anxiety which in turn can negatively impact one's sleep.

As a reviewer, I often compare data across different wearables but I suggest other people not to sweat over it. Just pick up a credible one like from the options below, and don't overthink it. Also, a sleep tracker, wearable or otherwise, might often not be 100% accurate compared to a professional sleep study (polysomnogram). However, it really is about trends over time. Again, don't sweat over it.

To reiterate, if you have any concerns about the quality of your sleep, it's a good idea to talk to a doctor. However, if you want to gain some insights about your sleep, fitness wearables are a great option. Instead of absolute numbers, keep a watch on trends to improve your sleep routine and in case of an anomaly, consult a sleep specialist. Sleep well!

Fitbit: When it comes to the fitness wearables available in India, Fitbit arguably offers the best sleep tracking with the most comprehensive insights. And that's across its portfolio – smartwatches including Fitbit Sense and Fitbit Versa 3 as well as trackers like Fitbit Charge 5 and Fitbit Luxe.

The heart rate sensor works in conjunction with the SpO2 sensor to unlock Estimated Oxygen Variation while you sleep. Large swings in blood oxygen levels can be a sign of sleep disorders like OSA. Additionally, the Fitbit Sense can even track when you store. This, and other insights like breakdown of duration, sleep stages, et al with detailed graphs, although require a Fitbit Premium.

The Fitbit Versa series health and fitness watch also has sleep tracking features.

The Fitbit Versa series health and fitness watch also has sleep tracking features.

Xiaomi: The Mi Band by Xiaomi has been one of the bestselling affordable fitness trackers for a while. The Mi Band 6, as well as Redmi Watch 2 Lite and Redmi Smart Band Pro, is a solid sleep tracking option if you're on a budget.

The sleep tracking is sometimes a little inconsistent for REM stage against a Fitbit Sense, but that's not a showstopper. The app offers a comprehensive sleep summary helping you to understand your slumber better. Considering its price, it's quite a rewarding proposition.

In the affordable segment, there's also the Amazfit portfolio with some good-looking smartwatches. It offers similar sleep analysis as the Xiaomi devices, but often tends to over-estimate time asleep, however, one must focus on trends instead of absolute accuracy.

Apple Watch: The Apple Watch, otherwise, the most widely popular smartwatch globally, only gained the ability to track sleep natively in 2021, and the company's take on sleep monitoring is quite limited.

There's no sleep stage tracking of REM, deep, and light cycles, nor is there any in-depth analysis of your sleep. There's also no Fitbit-esque 'sleep score'. Apple Watch does offer details about your sleep duration along with dark and light periods of your sleep. It's a basic breakdown, but also quite reliable. That said, Apple Watch users can try third-party apps for richer insights.

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