July 01, 2019

Do fitness trackers accurately measure sleep quality?

Q: My daughter's fitness tracker can display how well she sleeps if she wears it at night. Do fitness trackers give a reliable measurement?

A: Wearable fitness trackers that claim to also measure sleep have become quite popular. But their accuracy at this task is questionable.

Besides measuring the steps you take and other physical activities, fitness trackers often display information about your sleep and wake time. Some give an assessment of light versus deep sleep and how often you wake at night, based largely on motion detection.

However, when comparing data from these devices to that gathered with formal sleep studies, the trackers were largely inaccurate, particularly for people who wake often at night. In multiple studies, trackers were not found to be reliable in distinguishing between sleep stages. Nor did they measure up when judging time taken to fall asleep, the total sleep time or the overall sleep efficiency.

Despite this, if you're using one of these devices to monitor your sleep, there are few downsides. The device may help you notice patterns about your sleep habits that you can improve, such as maintaining a consistent sleep schedule. However, there's not much evidence that close monitoring of sleep results in either behavior change or improved sleep.

Rather than relying on a device to gauge sleep quality, consider how you feel when you wake up. If you don't feel rested and it's affecting your daily life, consider making changes to your sleep habits to see if things improve. If not, you may want to ask your doctor for a referral to a sleep specialist.