Zeo Sleep Manager, SleepTracker try to wake you when it’s best

“If people were meant to pop out of bed, we’d all sleep in toasters,” a wise, unnamed observer of the human condition once opined. (Some credit Garfield the cat.) Failing that, we could all sleep with gadgets that monitor our sleep and wake us at the moment we’re most ready to hit the ground running — or at least not stumbling around in a bleary-eyed daze.

A variety of devices are claimed by their makers to do just that — by keeping tabs on your sleep cycle and rousing you at a moment when waking is most natural. The key is to sound the alarm when people are moving between two specific phases of sleep — light sleep and rapid eye movement (REM) sleep, which is the stage where dreams or nightmares generally occur, says David Dickinson, chief executive for Zeo, makers of one device, the Zeo Sleep Manager.

At these transitions, Dickinson says, “you’re at the surface, already almost awake.” By contrast, waking out of another phase, deep sleep, is often not so fun: You may feel groggy and confused, wondering who and where you are and why your head weighs 500 pounds.


How to track the sleep transitions? Devices use different methods.

The Zeo Sleep Manager

The Zeo (, $149 for bedside version, $99 for device that interfaces with your smartphone) consists of a headband you wear to bed that measures brainwaves and translates them into the sleep stages they correspond to: In deep sleep, brainwaves are slow; in light sleep, they have ups and downs; in REM sleep they’re a lot like when you’re awake. The information is sent wirelessly to your phone or a bedside station, depending on which version of the Zeo you have. At the optimum wake time within a window you’ve chosen (from 15 to 45 minutes long), the alarm goes off.

But more than a device to help you wake up, the Zeo is a device to help you sleep, Dickinson says,"to help you learn about the third of your life you had no idea about before.” Its “sleep coaching” program encourages you to identify and put the kibosh on “sleep stealers” — too much caffeine or stress, say, or a less-than-prudent bedtime.

The Zeo is the first, and so far the only, alarm clock on the market that uses your brainwaves to decide when to wake you up.

The SleepTracker Wake Up Monitor

This was the pioneer in the field of minimally alarming alarm clocks, the first to aim — and claim — to wake you when you’re going in or out of REM sleep. But instead of measuring your brainwaves to determine when that happens, the SleepTracker — which takes the form of a very precocious watch — keeps a technological eye on your movements during the night: People are pretty much bed potatoes during deep or REM stages of sleep, but are more apt to kick, twitch, turn or squirm during light stages. (About $120 on, $149 at

Do the gadgets work? The evidence

The most sophisticated sleep monitoring is done in sleep labs, of course. There the gold standard of measurement is polysomnography (PSG), which takes account of multiple factors, including breathing, heart rate, eye movement and blood oxygen levels, as well as brainwaves and muscle activity.

Both the Zeo and the SleepTracker have funded studies comparing the accuracy of their own products with PSG results. The companies recognize that independent research would be seen as more reliable. “But no one’s going to do that,” says SleepTracker inventor Lee Loree, president of Innovative Sleep Solutions. “The companies have to fund this research, or it won’t get done.”

• In the Zeo study, published last year in the Journal of Sleep Research, measurements came from 26 healthy adults over two nights — the first was for getting familiar with the equipment and data were collected on the second. The PSG measurements were scored by two trained technicians from separate sleep labs, and the Zeo determinations of sleep stages agreed with each of them about 75% of the time. Not a perfect result, but then the two PSG scorers only agreed with each other about 83% of the time.

• The 2009 SleepTracker study looked at data collected from 18 subjects over one night each, comparing movements detected by the SleepTracker with movements detected by PSG equipment.

For all 18 participants, a total of 192 movement “events” were detected by the PSG equipment. The SleepTracker detected 176 of those, but missed 16. It also “detected” 11 events that did not really occur (meaning the PSG equipment did not detect them).

Loree freely concedes that his product can’t distinguish between REM and deep sleep — since you’re “catatonic” in both — whereas the Zeo probably can. But he argues that this doesn’t affect the SleepTracker’s effectiveness because in the last third of your sleep cycle — when you probably want to wake up — any period of motionless sleeping is likely to be REM sleep.

All in all, Loree says, “the Zeo and the SleepTracker probably get to the same place. They just go about getting there in a different way.” In fact, he believes the choice between them is mostly a matter of whether you prefer to wear a headband or a watch to bed.

• Neither the Zeo nor the SleepTracker study tested whether their high-tech alarms really wake you at the most propitious moment or not. But another alarm clock, the aXbo — a motion-based sleep monitor like the SleepTracker that its makers say will be available again in the U.S. later this year — reports a relevant study on its website.

After acquainting 40 volunteers with the aXbo one night, researchers used it to wake them up the next three nights in a row. On two of these nights, the aXbo, as is its wont, calculated the most favorable wake-up time during the 30-minute window it allows. But on one of the nights, randomly chosen and unknown to the sleepers, the aXbo rang amok — sounding at some sub-prime time in the window. According to their self-ratings, participants were significantly more cheerful and less drowsy on the mornings when the aXbo did its thing correctly.

What sleep scientists say

Behind every commercial sleep monitor, there’s probably a sleep scientist — quite possibly a bunch of them — and the products often assert their scientific pedigrees. “Zeo takes the science of sleep out of the lab and puts it into your hands,” says the Zeo website. “Turn your home into your personal mini sleep lab,” says aXbo’s.

But some sleep scientists believe the lab comparison may be a bit of a stretch. “These devices just give estimates,” says Dr. Clete Kushida, a professor of psychiatry and behavioral science at the Sleep Medicine Center at Stanford University. “They may not be as accurate as people think.”

That might be fine for people who simply want to learn more about their sleep, he says, but for people with actual sleep disorders, a little estimation could be a dangerous thing.

“Relying too much on these devices may offer a false sense of security,” agrees Dr. Alon Avidan, director of the Sleep Disorders Center at UCLA. Waking up naturally is still the best way, he adds: “Sometimes the answer for better sleep is simply to get more of it.”