THESE DAYS, it seems everyone has a Fitbit or something like it to track their steps and their general activity. Some people like to look at the information a fitness bracelet collects on their sleep. The idea is that knowing that you wake up 20 times at night is somehow supposed to help you sleep better. However, you could lose sleep trying to understand the inaccuracies caused by ineffective means of measurement. If you have sleep troubles, there’s a better way to fix it.
1. How Does a Fitness Tracker Measure Sleep?
Fitness trackers on the market use a few different assessments to determine how well you are sleeping. The most common devices have accelerometers to measure your movement, as well as its direction and speed. They claim that the data collected tells you how long you are asleep, as well as your sleep stages and how often you wake up. Some wearable devices also include a heart rate monitor, which also provides some data about the degree of relaxation you reach at various points throughout the night.
2. Are the Fitness Trackers’ Measurements Accurate?
If this sounds about as scientific as beer pong, it sorta is. Many experts criticize the use of these devices for sleep, saying that they can give you a very unclear picture of your actual sleep habits. For example, studies from 2011 and 2013 showed that fitness trackers seriously overestimated the amount of sleep adults get, and significantly underestimated the minutes of sleep children get by almost two hours. Experts argue that simply measuring movement cannot distinguish between lighter and heavier stages of sleep, since movement is about the same for both. For an accurate measurement of sleep, you need to measure heart rate and breathing, as well as movement, which none of the wearable fitness trackers can do.
3. How Can This Information Help My Sleep?
It is certainly true that knowledge cannot really hurt you, but only if that knowledge is not as wrong as sandals with socks. Since the assessments fitness trackers make for your sleep cannot replicate the equipment sleep disorders experts use in a sleep lab test or electroencephalography (EEG), the use you get from it is very little. The best the fitness bracelet can do is to confirm that you get plenty of good, quality sleep when you actually do. Many people in the field of sleep disorders worry that the fitness trackers, in overestimating adult sleep, may give wearers with sleep issues a false sense of security about their sleep health. In short, if the fitness bracelet prompts you to take the next step to improve your sleep hygiene (i.e., through the development of new habits or the purchase of a new mattress), the fitness tracker is helpful. That is basically the extent of it.
4. Is There a More Effective Sleep Monitor?
There really is no effective replacement for the kinds of tests you could have during a sleep study, which would also include monitoring of the oxygen saturation of the blood. However, there are a few other types of sleep monitors that may have a higher degree of accuracy. Some simply measure movement, and are just as ineffective as the fitness trackers. Others will also track heart rate, respiration, body temperature, skin response and more. Most of these products offer an auxiliary device attached to the body sensor that determines the amount of light and noise in your bedroom while you sleep. Some also use this data to determine the best time to wake you up within your preferred time range, so you wake up at the most opportune time during your sleep cycle. In this capacity, they can be more practical for you.
One such monitor is SmartWake by Verlo, the world's smartest alarm clock. Introduced just two weeks ago, SmartWake uses a sensor (placed under the mattress), and an app on your smartphone. SmartWake identifies sleep cycles by measuring heart rate, breathing and movement and then calculates your lightest sleep phase – the best time to start the day – within your selected alarm time. In addition, SmartWake provides insight into your sleep patterns so you can improve your sleep habits.
In general, using a fitness bracelet to measure sleep may seem like a nice additional feature for the device. However, they can’t really make you sleep better. If you really want to find the best way to stop counting sheep, purchase a sleep monitor or arrange for a sleep study.