Activity monitors may work better for exercise than for sleep
Activity trackers, such as FitBit, might help you see your general sleep patterns, but they are limited in their usefulness. Since they may not be as helpful as they promise, interpret what they tell you with a grain of salt—at least for now.
Sleep is complicated, and in order for an analysis to be as meaningful as possible, it must be comprehensive, as well as precise. A lab sleep study is the most thorough type of analysis. It involves a stay in an overnight facility, in which a technologist records multiple biological functions during sleep, such as brain wave activity, eye movement, muscle tone, heart rhythm, and breathing via electrodes and monitors placed on the head, chest, and legs.
An activity tracker, on the other hand, is a wearable digital device that measures just one thing (arm movement) with a detector called an accelerometer. So some argue that its analysis is not thorough enough. However, as anyone who has spent time in a sleep lab knows, sleeping in a bed that's not actually your own in an unfamiliar environment may not be comfortable—and may not be representative of how you generally sleep at home. For that reason, the appeal of using a more basic device privately, in your own bed, for a fraction of the cost is understandable—especially if you are healthy and don't suspect that you have any major sleep problems. Perhaps, for example, you simply want to know how much you sleep each night.
But if you suspect that you may have a sleep disorder, right now, undergoing a full lab sleep study is still the gold standard. When you think about how difficult it is to diagnose a common sleep problem such as insomnia, it stands to reason that monitoring sleep isn't as straightforward as, say, monitoring the number of steps that a person takes each day. Typical trackers aren’t yet sensitive or sophisticated enough to replace a doctor’s exam or diagnostic processes. What’s more, trackers could falsely suggest that a person with a sleep disorder does not have a problem, and discourage that person from seeking necessary medical attention.
That said, there should be more accurate options in the near future. The National Sleep Foundation has partnered with the Consumer Electronics Association and formed a “Wearable Sleep Monitoring Equipment Group” to help the development of sleep technology.