How To Use and Understand Your Sleep Tracker Data

You slept a total of seven hours and 36 minutes last night.

So what?

You know the total because you wore a fitness monitor to bed. You synced it with your smartphone. In the morning, you looked at the result: 7 hours, 36 minutes.

Now what are you supposed to do with this information?

Sleep trackers usually measure movement, not brainwaves. Most work through the use of an accelerometer. That’s the part of your fitness monitor that also counts your steps when walking.

Current sleep trackers are based on relatively old technology. In the 1970s psychiatric patients’ movements were monitored during studies. It became obvious to researchers which movements correlated with being awake and which indicated sleep. Researchers made tweaks in improvement over time, gradually improving the devices until recent times when “some of the best minds got interested in the devices and started working on them.”

Michael Grandner, director of the Sleep and Health Research Program at the University of Arizona College of Medicine – Tucson, appeared on the Sleep Junkies podcast early in March to discuss sleep technology.

“They give you a window on sleep that you don’t normally have,” he said of the devices.

Normally sleep interferes with memory. Sleep trackers can give you a way around that. Sleep technology continues to improve, adding he expects it to continue to improve in the coming years.

The whole value in a sleep tracker, Grandner said, is the pattern it shows over time. You don’t look at just one night. Rather, you have to look at a whole series of nights.

“They can work well enough for a ballpark guess (as to how you’re sleeping),” he said.

Grandner compared sleep trackers to bathroom scales. As one would diet and weigh themselves, you look to see what direction the numbers are going in. Trends are what’s important.

New devices are always being produced. Scientists and engineers add new features.

The device might report on your sleep stages, he said.

That’s not important. “Worrying about sleep stages is like worrying about the oxygen in the air.”

Sleep stages are a way of describing the process of sleep.

If you were worrying about the level of oxygen in the air, you’d go about cleaning up the environment. You’d make sure the oxygen you were breathing was clean.

Continuing the analogy, he said if you were worried about your stages of sleep, you’d make sure you optimized your sleeping environment.

Ultimately, the stages of sleep take care of themselves.

Expect more of these devices to come on the market in the coming years, he said.

Not every one of these devices is going to be validated by testing, he said. That would be impossible. Yet, just because they’re not validated, however, doesn’t mean they’re invalid.

Final testing needs to be done in a sleep lab.

If you wear a sleep tracker, maybe it’s a good idea to make a note of what your sleep tracker says in your dream journal if you’re convinced it’s relatively accurate. Since they’re based on movement, things like your bed partner or pet’s movement can throw them off. The goal isn’t precision. Accelerometer-based technology isn’t ever going to be precise.

Rather, as Grandner put it, it’s to be in the same ballpark.

Further reading:

Do a study of one

Four ways to put the scientific method in your life

Learn anatomy and physiology before you need it


James Cobb, RN, MSN, is an emergency department nurse and the founder of the Dream Recovery System. His goal is to provide his readers with simple, actionable ways to improve their health and maximize their quality of life. 


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