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The Science behind Sleep Trackers

There is a growing number of devices available that claim to accurately track your sleep. But how do they work? And just how accurate are they? It turns out that not all sleep trackers are created equal, and some may be very inaccurate.

There are two types of sleep trackers: the wearables and the nearables. Wearable devices are worn by the user and include everything from watch-like devices to t-shirts, even devices which are placed on your finger like THIM. The nearables include devices which measure sleep from a distance. They incorporate smartphone apps, bed sensors and gadgets which sit on your bedside table.

Many sleep trackers, particularly the wearable kind, measure body movement to track sleep. If the user is moving a lot, it’s assumed they are awake, and if they are not moving much/at all, they must be asleep. This is the most popular method of sleep tracking, particularly by wearable devices.

For an average sleeper, this method is fairly accurate and can paint a reasonable picture of the user’s sleep. However, these devices can be very inaccurate for some people. The most common problem is that the device says they are asleep when they are actually awake, which is typically found for those who spend a lot of time awake in bed whilst staying very still. If this sounds familiar to you, see our recent blog for tips on how to improve your sleep.

Some devices use other methods to track sleep, including snore recognition, temperature, body position, heart rate and light. Some of these methods have little research to support the accuracy, others have none. This means that we have very little evidence, if any, to suggest that they are accurate at tracking sleep.

Generally, wearables are more accurate than nearables. But even wearable devices which use well-researched methods of tracking sleep like measuring body movement may still be very inaccurate. Why? The problem is that even though many sleep trackers use the same methods to track sleep, each and every sleep tracker has a different way of calculating sleep. Two wrist-worn devices which both measure movement can give very different data about a person’s sleep.

Many sleep trackers have absolutely no evidence available about their accuracy. This means that we don’t know whether they are accurate at tracking sleep. Under current laws, sleep trackers don’t require any evidence of their accuracy before being sold to consumers. These devices could be completely inaccurate and the consumer would be none the wiser.

In recent years, sleep researchers have been testing the accuracy of the most popular sleep trackers. Some are reasonably accurate, but many are sub-par. So if you are on the hunt for a sleep tracking device – do your research. Search the web for information about the accuracy of your desired sleep tracker before purchasing. Some companies have information available on their website about the accuracy of their devices. If no research studies have been conducted, think twice before purchasing. These devices may not be worth your money.

By Hannah Scott

Hannah is a PhD (Research) Candidate from Flinders University


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