How Does Sleep Tracking Works: Is it Reliable?

How Sleep Tracking Works

We have come a long way, these days we have smartwatches that can measure everything from Heart rate, Spo2, Exercise activity, and even sleep tracking too.

So today, let’s see how Sleep Tracking on a smartwatch or on a fitness tracker works? is it reliable at all or not?

How Does Sleep Tracking Work?

While you’re sleeping, the smartwatch will use a gyroscope, accelerometer, and even heart rate sensor to finger out your body poster and heart rate, after that, the smartwatch or even fitness Tracker will run all the tests and figure out how many hours you have slept.

The gyroscope and accelerometer sensors help to track body movements. For example, whether you’re sitting, running, hand movement, etc.

Some smartwatches also use the heart rate sensor to monitor heart rate fluctuation. The heart rate is lower when you’re in a deep sleep. In short, by measuring the heart rate data, the watch will give you more accurate sleep data.

When I was doing research for this article, I come across with Fitbit website and it says:

When you haven’t moved for about an hour, your device assumes that you’re asleep. Additional data—such as the length of time your movements are indicative of sleep behavior (such as rolling over)—help confirm that you’re asleep.

Also, some of the premium smartwatches use everything from heart rate sensor, SpO2 sensor, gyroscope, and accelerometer to give you slightly more accurate data.

Related: How Does SpO2 Oxygen Sensor Work In Smartwatch

Now, to do all the tasks at the same time smartwatch needs to have good sensors and that’s the main reason why we don’t get accurate sleep data in budget smartwatches.

If you’re more curious about sleep then I would highly recommend you read Why We Sleep by Matthew Walker, the book talks about everything about Sleep.

Should you Wear Smartwatch or Fitness Tracker While Sleeping?

Now, this is personal preference, some people don’t like to wear anything on hand while sleeping and some people do.

If you ask me, I do wear Fitbit while sleeping because I want to know how much I sleep and the pattern of my sleep cycle.

Also, if you feel uncomfortable while wearing a smartwatch then you can also use the Smart Rings which are dedicated made for sleep tracking, so if you’re concerned about your sleep then, try to use smart rings.

In short, wear a smartwatch or fitness tracker for two or three nights and see the experience and if you feel uncomfortable then leave it…

Can Wearing Smartwatch at Night Affect the Sleep or Health?

There is no official claim by any organization that wearing smartwatches or fitness trackers can harm your health or sleep cycle.

Also, it’s not like we will wear smartwatches 24/7, we will take bath or do any other activity, so you won’t face any problems while wearing a smartwatch while sleeping.

What are the Benefits of Sleep Tracking?

Tracking sleep can help you in different ways, let’s say, you’re feeling that I’m not getting enough sleep for days then you can just wear a smartwatch to monitor your sleep.

Now, there are four sleep stages:

NREM Stage 1: This is the beginning stage when your body and brain will slow down, this brief period of sleep lasts for around five to 10 minutes.

NREM Stage 2: This is also called light sleep too, during this stage, your heart rate will slow down, and your eye movement stops. According to the American Sleep Foundation, people spend approximately 50% of their total sleep time during NREM stage 2, which lasts for about 20 minutes per cycle.

NREM Stage 3: This stage is called deep sleep, during this stage, your muscles and brain are at complete rest. Slow brain waves known as delta waves begin to emerge during NREM stage 3 sleep and this stage is also referred to the delta sleep too.

REM Sleep: During REM sleep, your brain’s activity most closely resembles its activity during waking hours. This is that time when you have dreams. REM sleep begins approximately 90 minutes after falling asleep.

Now, if you’re using any smartwatch then the smartwatch brand will give you an application where you will be able to see all the sleep stages while the app will also suggest you if you’re not having good sleep.

Are Smartwatches Reliable?

This depends on which smartwatch you’re using, if you’re a cheap smartwatch then there is a chance that you won’t get accurate sleep data but if you’re using good smartwatches then you will get close to accurate data.

In my testing, the Apple, Fitbit, and Galaxy Watch provide close to accurate sleep data.

Now, this doesn’t mean other brands don’t provide accurate data. in the end, it all depends on the quality of the sensor used by smartwatch companies.

In short, do your research before you spend money on smartwatches.

Or you can visit this page to find smartwatches within your budget.


That was it, we have discussed everything that you need to know about how sleep Tracking. By the way, as I have said, the smartwatches won’t give any side effects, so there is nothing to worry about.

Also, if you can, take off the smartwatch when you take bath or while doing any other activity. What I’m saying is don’t wear a smartwatch 24/7.

Still, Have questions? do let me know in the comments.

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