Sleep Trackers: What are they and do they work?

With the growing recognition of the importance of sleep for overall health, commercially available sleep trackers have grown in popularity. 

Approximately 25% of Americans track their sleep. Whilst there is no data here in Australia, it is likely to be similar. 

There are many different types of sleep trackers and their main purpose is to enable individuals to conveniently monitor and analyse their sleep, independent of a healthcare professional. Sometimes they can be used in the healthcare setting for research purposes. However, there is varied data on the reliability and  performance of these widely used sleep trackers.

What are sleep trackers?

Sleep trackers are devices used to monitor and analyse sleep.

Sleep trackers are used mostly by individuals at home and rely on sensors to detect other physical signs, like light, heart rate and body movement to estimate sleep via these signals. They do not rely on signals from the brain. 

There are different types of sleep trackers:

• Wearables are trackers that are worn on one’s wrist and remain on the sleeper all night.
• Other trackers (known as ‘nearables’) may rest on the mattress or, under the mattress or next to the bed collecting information unobtrusively, i.e. not touching the sleeper (‘airables’).

The gold standard for a sleep study is a laboratory-based sleep test known as a polysomnogram. This is a multi-channel test that tracks electrical patterns that indicate sleep, and stages of sleep, directly through brain activity. 

What do sleep trackers monitor?

There are many aspects of your sleep in which sleep trackers can monitor. They include:

Sleep Duration

You might be interested to know your sleep duration, by tracking the time you’re inactive, i.e., lack of movement). Certain sleep trackers can record when you fall asleep at night and when you wake in the morning. Some people prefer this type of accuracy rather than their own estimate.

Sleep quality

Sleep trackers can detect interrupted sleep, letting you know more about your sleep quality like how much you’re tossing and turning or waking during the night.

Sleep stages:

Some tracking systems track the stages of your sleep and time your alarm to go off during a period when you’re sleeping less deeply.

Environmental factors

Some devices can track environmental factors such as the amount of light or temperature in your bedroom.

Lifestyle factors:

Some trackers prompt you to enter information about activities that can affect sleep, such as how much caffeine you’ve had, when you’ve eaten or whether your stress level is high. Some may have built in sleep tips too based on your data. Some people are able to be more conscious of what lifestyle factors such as alcohol and caffeine can do to their sleep, by using sleep tracking technology.

How can you track your sleep?

You can choose many different commercially available ways to track your sleep as outlined above. However, this will depend on the type of tracking device used. 

• Wearable devices or ‘wearables’, such as smartwatches and ring-shaped devices, are generally worn by users to track sleep using sensors like photoplethysmography (PPG) sensors and accelerometers. 
• This simply means that they use non-invasive technology that uses a light source and a photodetector at the surface of skin to measure the variations in blood circulation (PPG), or they focus on measuring movements (via accelerometers). So in other words they monitor light, heart rate, breathing rates and movement.  
• Nearable devices or ‘nearables’, placed near the body without direct contact, have radar or mattress pads to detect subtle movements during sleep and use an algorithm that can detect how much movement equates to sleep and how much movement equates to wakefulness.
• Airable devices or ‘airables’ use mobile phones to analyse sleep via built-in microphones or environmental sensors to make estimates of sleep via these sounds or heart-rate monitors.

Are there drawbacks or risks associated with tracking your sleep?

Yes, there may be drawbacks or risks associated with tracking your sleep. 

The two aspects to be cautious about are: 

1. the accuracy of your data 
2. the tendency for some people to get a little too fixated or anxious about their sleep as a direct result of too much monitoring and thinking about their sleep.

Are sleep trackers accurate?

The answer is two-fold. Although sleep trackers are becoming quite accurate at detecting sleep from wake, the classification of sleep stages remains unreliable and inconsistent, so it’s important to be mindful of the data your sleep tracker is providing.

In terms of people tending to get too anxious or obsessed over their sleep data, this has become so common there is now a name for this condition – orthosomnia. 

Orthosomnia is not a medical disorder – it is more accurately described as an anxiety phenomenon which is affecting people who obsess over the results of their sleep trackers.

Although current knowledge of orthosomnia is based only on small case studies of few participants, when people obsess and worry over sleep hours this can develop into unhelpful behaviours such as spending a longer time in bed in order to improve their sleep tracker data, which paradoxically may worsen sleep quality and quantity.

What other ways are there to improve sleep?

Sleep experts who have experience with treating sleep disorders have not driven or created the concept of sleep tracking and sleep trackers are not considered a solution or strategy for improving sleep. Their value lies in enabling people to monitor and analyse their own sleep data, independent of a healthcare professional. 

The other advantage or utility of commercially available sleep trackers is that they can enable large scale monitoring of population-based sleep, conveniently and without large expensive equipment. Via this observation and biofeedback, the sleep trackers may have the potential to alter people’s sleep behaviours particularly if the person observes that their sleep is more disturbed after certain behaviours (such as drinking alcohol). However, there is also the risk of sleep becoming more elusive due to sleep anxiety increasing.

The best ways to improve sleep lie in domains outside of thinking too much about your sleep. 

The top 5 principles for good sleep are:

• Value sleep
• Prioritise sleep: ensure you have made time for getting enough sleep
• Personalise it to suit you and your age, sex, job and lifestyle
• Trust in your sleep systems and yourself (don’t panic if it’s not perfect all the time)
• Protect sleep: a bit like principle 2 above, you need to make sure you don’t let everything else come between you and getting adequate sleep.

The sleep experts state that sleep tracking isn’t always helpful, nor is it always harmful. They state that there is no commercially available sleep tracker that sends a stronger signal about whether you’re getting enough sleep than your own brain and therefore if you’re alert (without caffeine), able to concentrate, feeling you’re able to have a good quality of life at work and home, then you’re probably getting enough sleep.

If you’re experiencing frequent troubles with your sleep, it’s important to see a healthcare professional for personalised advice. 

Summary

Sleep trackers can offer some great insight into the duration, quality, stages, and lifestyle factors of your sleep. Keep in mind that whilst useful, accuracy may vary.

Rather than just relying on your sleep tracker, consider focusing on the five principles of good sleep.

This can help you improve your overall sleep and help ensure you’re not too fixated on the numbers.

Related reads:

• How to sleep better | 5 tips from a sleep expert
• How to Get More REM Sleep
• What is sleep & why do we need it?

Reviewed by the healthylife Advisory Board March 2024.