Summary
Things you should know:
- It is important to remember that sleep trackers can vary in accuracy for determining sleep stages. While these devices can give a rough estimate, they are not a perfect measure.
- Rather than closely examining nightly sleep stages, it may be more helpful to look at the patterns of your sleep (bed and wake times) over time.
- Understanding your sleep patterns may help identify and adjust behaviours that negatively impact your sleep, such as your bedtime routine and sleeping environment.
- If you are concerned about your sleep, talk to your GP.
Sleep trackers
High-tech wrist watches, smartphone apps, and bedside sensors have been developed to monitor your sleep patterns. These trackers often provide information about your bedtimes and waketimes and how long your spent in each sleep stage. Although it might be fun to pore over data you have collected about yourself, it is important to keep the pros and cons in mind when using these new sleep tracker technologies
How do sleep trackers monitor sleep?
Most trackers that you wear on your body (called 'wearables’) measure your sleep via an accelerometer: a sensor which measures your movement. Newer devices also include heart rate and oxygen level sensors, which can be used to provide additional sleep information including breathing patterns and heart rate activity.
Some devices are placed on or under your bed or on your bedside table. These devices are called ‘nearables’. The technology that these devices use varies widely, and include sound, pressure, and radar sensors. Essentially, they also attempt to measure movement and/or breathing to estimate sleep, similar to wearables, but they do so via different sensors.
What information do sleep trackers provide?
The information that sleep trackers provide can vary widely, depending on what they measure. Most new sleep trackers provide the following:
- Sleep duration: how long the tracker thinks you slept for.
- Sleep stages: how long you spent in different stages of sleep. Often, this includes ‘light’ and 'deep’ sleep.
- Sleep pattern: when you went to bed and when you got out of bed, i.e., your ‘sleep schedule’.
Some sleep trackers also give 'sleep scores’. It is often unclear how these scores are derived and what they mean beyond a general indication about your sleep.
Some sleep trackers also provide information about breathing disturbances during the sleep period. This information may raise warning signs about your breathing during sleep which you should discuss with your GP, especially if it persists.
How do these new technologies compare with the gold standard sleep test using brain waves?
Some sleep trackers have undergone lots of research to validate them for measuring sleep, while others have undergone very little testing. For this reason, the information from sleep trackers should only be used as a general guide unless it is being used as part of your clinical care (if a physician advises you to use the device, then you can be confident that the device is accurate). Otherwise, you should not make important health decisions based on the data from sleep trackers (1).
Generally, the more popular, 'big name’ devices are relatively accurate for estimating sleep, but the struggle to estimate sleep stages. In other words, these devices can usually tell when you are asleep, but they are not very good at telling what sleep stage you are in (2).
What are the potential benefits?
These devices raise awareness of sleep health and sleep issues. They might also help some people understand and review their sleep and wake patterns, and this may ultimately improve their sleep. For example, noticing a pattern of repeatedly going to bed late and sleeping less than required may help the user adjust their sleep habits to allow for longer sleep.
Sleep trackers could also show if you are getting lessor more disturbed sleep than you might expect. This might lead you to seek treatment or change lifestyle habits. See Understanding and Helping Poor Sleep as a good starting point or discuss with your GP.
What are the potential dangers?
For most people, using a monitor to track sleep isn't going to be a problem.
However, if you have insomnia tracking sleep might lead to anxiety about not getting ‘enough’ sleep. Rather than encouraging you to change habits to help improve your sleep, this anxiety can sometimes lead to more difficulty sleeping. For this reason, you may want to avoid using sleep trackers if you notice that sleep tracking is negatively impacting your sleep.
These devices may also not be as accurate for people with some sleep disorders, so they should be interpreted with caution under these circumstances.
The key take-away:
Sleep trackers will give you a good overview of your sleep, but if you think there is a problem with your sleep, you should talk to your GP. Collecting data about yourself can be very interesting. Just remember that sleep trackers point to general trends in your sleep: the specifics need more sophisticated assessment.
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References
(1) Khosla S, Deak MC, Gault D, et al. Consumer sleep technology: An American Academy of Sleep Medicine position statement. Journal of Clinical Sleep Medicine. May 15 2018; 14(5):877-880. doi:10.5664/jcsm.7128
(2) Chinoy ED, Cuellar JA, Huwa KE, et al. Performance of Seven Consumer Sleep-Tracking Devices Compared with Polysomnography. Sleep. Dec 30 2020; doi:10.1093/sleep/zsaa291