World Sleep Society has published recommendations on the use of consumer health trackers (CHTs) for sleep measurement by professionals. With so many health trackers on the market assessing sleep in different ways, it can be difficult to know exactly what your tracker is telling you about your sleep. When investing in and using a CHT, be sure to consider the following three factors.
1. A sufficiently good-quality CHT can provide valuable sleep and health information
There are many CHTs on the market with varying degrees of tracking. If you are interested in recording your sleep, look for one that will measure movement, heart rate, respiratory rate, and blood oxygen levels. While you will not get a full overnight oxygen profile, the information may provide useful guidance. Health tracker devices should be consistently worn snugly against the skin and positioned according to the manufacturer’s guidelines to improve accuracy. It should be noted that most CHTs are designed based on healthy working-age adults.
A good quality CHT can give feedback on sleep duration and time spent in different stages or types of sleep. Sleep duration information is generally more accurate than sleep quality measurements, and age-appropriate data is scarce. Many CHTs use movement data to determine sleep and its stages. When we fall asleep, movement is reduced. It is further reduced in deeper Non-Rapid Eye Movement (NREM) sleep, and movement is absent during Rapid Eye Movement (REM) sleep. Keep in mind that even the best sleep trackers can get it wrong sometimes. Because they gauge sleep primarily on movement, CHTs may mis-classify time in bed not moving as sleep when in fact you may just be lying still trying to fall asleep. Children and the elderly are at the highest risk of inaccuracies. High-resolution movement data has been used to infer pulse rate and respiration. Heart rate and respiration may also be measured from pulse information by CHTs. Changes in heart rate, slowing or increasing, can indicate quality of sleep. Normally, with good sleep the heart rate drops.
A CHT may be useful to alert you of poor sleep health including irregular sleep and delayed sleep timing. Some devices can screen for sleep apnea risk and circadian rhythm disorders. If your sleep is consistently poor, or you suspect a sleep disorder, consult a sleep professional. A formal home sleep study or laboratory sleep test may be ordered to confirm the results.
2. Focus on trends and patterns, not individual scores. Use scores to motivate, not compete
Everyone has an occasional night of poor sleep, but it doesn’t help to worry about it. Often the worry will lead to more nights of poor sleep. When reviewing sleep data, it is better to look at overall trends. Is your sleep on the weekend the same as during the week? Are there days when you have difficulty going to sleep? What time did you fall asleep? Do you wake up after falling asleep? If you see sleep patterns that can be improved, start there. It may be helpful to keep a sleep journal along with the tracker. Some trackers have sleep journals built in. Note things that may affect your sleep, such as what or when you ate, stressors, or the cause of a late night. It will then be easier to assess your sleep tracker results.
Sleep scores may be used to motivate the user to better sleep. Everyone is different, and sleep trackers measure sleep a bit differently, so it is unhelpful to compare sleep scores. Each CHT manufacturer has their own set of algorithms and measurements. Currently, comparing one against another won’t provide an accurate picture of your sleep. However, comparing how you slept last week against how you slept this week may be helpful in motivating you to get better sleep.
3. Sleep data is less reliable if sleep is significantly delayed, very short, or fragmented
Trackers are programmed to measure a nightly block of sleep. Sleep outside that block may not be accurately reported. For instance, nap detection varies between devices and is not always reliable. It is difficult to know if the nap was intentional or spontaneous. This is where keeping a sleep journal is helpful.
It is important to note that on nights when total sleep time is 80-85% or less, the accuracy of the total sleep time may be inaccurate.
For the most accurate results from your wearable health tracker, wear the device according to manufacturer directions, get consistent sleep, watch for patterns, and keep a sleep journal to tell the story behind the sleep. This information can give you a good picture of your sleep health.
The full text article is available: World Sleep Society Recommendations for Use of Wearable Consumer Health Trackers that Monitor Sleep.