Have your friends been showing you their sleek, futuristic-looking sleep trackers on their wrists, and enthusing about how their useful gadgets are improving their health and lifestyle?
Out of curiousity, you do a quick search online and it reveals countless articles and reviews raving about sleep trackers, tempting you to open your wallet for one. If it’s good for you, why not right?
But wait, are they as useful as they claim to be? Or are they all hype and no help?
Before you head to the nearest store to get your very own sleep tracker, here are some things that could help you understand these technology a bit better.
Types of sleep trackers
There are a several types of sleep trackers in the market that differ in terms of usage and sleep tracking capabilities.
The most popular type thanks to the rise of wristband fitness trackers that double as sleep trackers too. Wearables can also come in the form of a ring. You wear these devices while sleeping and they typically collect data such as movement, heart rate and even breathing patterns to measure quality and duration of sleep. These devices are usually multipurpose, allowing you to track other things like daytime physical activity, calories burned, or log your food intake.
- Bedside devices
These are usually placed next to the bed and does not require any skin contact with your body. Through echolocation (a reflection technique that fires out ultra-low power radio waves), it can detect any movements and your breathing rate. Some can also store information about temperature, humidity, ambient noise and light.
- Bed sensors
These sensors are positioned under your sheets or mattress and can track similar information as the above two types. However, what is unique about this type of sensors is that you can place two of them under your bed to record you and your partner’s sleeping data.
Some common capabilities of these devices include:
- Sleep duration
The time from falling asleep to waking up in the morning.
- Sleep quality
This is defined as how quickly you fall asleep and stay asleep. Trackers can determine the quality of your sleep by recording your movements, whether you have been tossing and turning or waking during the night, resulting in poor quality sleep.
- Sleep phases
While we sleep, we go through phases of light to deep sleep. By tracking your phases, these devices can time your alarm to go off during a phase (sleep stage) when you’re sleeping less deeply.
- Environmental factors
Some devices, such as bedside sleep trackers or bed sensors, record environmental factors like the amount of light or temperature in your bedroom.
- Lifestyle factors
Some trackers are more detailed and will take into account other possible factors of sleep such as caffeine intake, food intake and stress levels to present more accurate findings. Such devices will usually prompt you to input information.
It's easy to get caught up in all the fancy features and styles of a sleep tracker, but to keep in mind to prioritise comfort (especially if it's a wearable or going under your sheets). Otherwise, you probably won't use it.
Not all trackers work the same
One thing to note is that different brands and models differ in the way they estimate sleep and it’s stages, and there is a lack of standardisation of sleep algorithms.
For example, a study into 6 different brands of sleep trackers showed that 3 out of 6 sleep trackers solely use movement as an estimate of sleep, while only 1 brand uses information from multiple sensors, including movement and heat flux sensor, to detect “in and out of bed” and estimate sleep stage using an artificial neural network (ANN). To detect the onset of sleep, 3 brands measure it by seeing if movement drops below a certain threshold, while other brands use lowered heat flux or heart rate to determine so. Additionally, though all sleep trackers provide the total time awake, total time asleep, and sleep quality index, each brand would have its own definition of sleep quality index, which makes it difficult to determine which brand provides the most accurate information.
The gold standard for the measurement of sleep
The hard truth is that most commercial sleep trackers are still not advanced enough to provide data that matches the gold standard for sleep measurement. Polysomnography (PSG), which is a study done by a doctor in a sleep lab while you’re fully asleep with electrodes on your head. They typically observe the detection of your brain waves and heart rate, and recorded sleep cycles chart to identify any sleep disorders. Sleep measurements determined by PSG include the following:
- Total sleep time (TST)
The amount of time that you spent sleeping
- Sleep efficiency (SE)
The amount of time you spent sleeping, given the total time you have to sleep
- Sleep onset latency (SOL)
The time taken to fall asleep
- Wake after sleep onset (WASO)
The amount of time spent awake after initially falling asleep
However, PSG is time-consuming and expensive to do on a daily basis, which is why commercial sleep trackers become a more popular option due to affordability.
Some brands of sleep trackers such as Fitbit were shown to be able to match the accuracy of PSG in terms of recording TST and SOL. However, in terms of SE and WASO, the accuracy is still lower as compared to PSG. Interestingly, the same research has shown that the accuracy of TST and SE in insomniacs were poorer than in good sleepers.
Hence, if you are suffering from a sleep disorder or suspect that you are suffering from one, it is important to keep in mind that sleep trackers may not present the most accurate information about your sleep.
Overall, sleep trackers can only provide a good guesstimate of your sleep patterns, and the only real way to measure sleep accurately is through PSG.
Don’t lose sleep over your sleep tracker
Sleep trackers offer a simple and convenient way to be more aware of your sleeping patterns, but keep in mind not to get too stressed over the numbers every day and let what you see affect how you feel. As mentioned above, sleep trackers are limited in their accuracy of sleep measurements, so don’t end up lying awake in bed feeling anxious over not meeting your sleep goals.
If you have any concerns about the quality of your sleep, it’s always a good idea to consult a professional. Otherwise, if you are a healthy person who just wants to gain some insights of your sleep routine, then sleep trackers might be a good option for you.
Here’s an advice from Active Health Coach Mason Tan: “Overthinking about your sleep can actually lead to poorer sleep! There are other ways to gauge your sleep quality apart from sleep trackers. A sleep diary for a start might be useful to help you track how quickly it took you to fall asleep, how many times you woke up during the night and how you felt through the day.”