Apps and fitness trackers that measure sleep: Are they useful?
ABSTRACT
Consumers have become increasingly interested in using fitness trackers and smartphone applications to quantify sleep. The devices claim to measure various sleep parameters, with the result that patients are now showing the data from their devices to their clinicians with concerns about their quantity or quality of sleep. In general, these devices have major shortcomings and limited utility, as they have not been thoroughly evaluated in clinical populations.
KEY POINTS
- Wearable fitness trackers tend to perform better than smartphone applications, which are more prone to interference from bed partners and pets.
- Sleep data from tracking devices are less reliable in patients with fragmented sleep and insomnia.
- In normal sleepers, devices tend to measure sleep duration with reasonable accuracy, so that one can tell if a patient is getting too little sleep or reassure someone who is getting enough sleep.
- Devices may help identify patients with poor sleep hygiene or atypical circadian rhythms.
Detecting circadian rhythms
A device may show that a patient has a clear circadian preference that is not in line with his or her daily routines, suggesting an underlying circadian rhythm sleep-wake disorder. This may be evident by bedtimes and wake times that are consistent but substantially out of sync with one’s social or occupational needs.
Measuring overall sleep duration
In people with normal sleep, fitness trackers perform reasonably well for measuring overall sleep duration. This information could be used to assess a patient with daytime sleepiness and fatigue to evaluate insufficient sleep as an etiologic factor.
Table 3 summarizes how to evaluate the data from sleep apps and fitness tracking devices for clinical use. While these features of consumer sleep tracking devices could conceivably help in the above clinical scenarios, further validation of devices in clinical populations is necessary before their use can be recommended without reservation.
ADVISING PATIENTS
Patients sometimes present to clinicians with concerns about the duration of sleep time and time spent in various sleep stages as delineated by their sleep tracking devices. Currently, these devices do not appear to be able to adequately distinguish various sleep stages, and in many users, they can substantially underestimate or overestimate sleep parameters such as time taken to fall asleep or duration of awakenings in the middle of the night. Patients can be reassured about this lack of evidence and should be advised to not place too much weight on such data alone.
Sleep “goals” set by many devices have not been scientifically validated. People without sleep problems should be discouraged from making substantial changes to their routines to accommodate sleep targets set by the devices. Patients should be counseled about the pitfalls of the data and can be reassured that little evidence suggests that time spent in various sleep stages correlates with adverse daytime consequences or with poor health outcomes.
Some of the apps used as alarm clocks claim to be able to tell what stage of sleep people are in and wait to awaken them until they are in a light stage, which is less jarring than being awakened from a deep stage, but the evidence for this is unclear. In the one study that tested this claim, the app did not awaken participants from light sleep more often than is likely to occur by chance.17 The utility of these apps as personalized alarm clocks is still extremely limited, and patients should be counseled to obtain an adequate amount of sleep rather than rely on devices to awaken them during specific sleep stages.
The rates for discontinuing the use of these devices are high, which could limit their utility. Some surveys have shown that close to 50% of users stop using fitness trackers; 33% stop using them within 6 months of obtaining the device.24 Also, there is little evidence that close monitoring of sleep results in behavior changes or improved sleep duration. Conversely, the potential harms of excessive monitoring of one’s sleep are currently unknown.
