Can someone tell their brain to wake them up just ahead of the alarm?

Maybe this happens to you sometimes:

You go to bed with some morning obligations on your mind, maybe a flight to catch or an important meeting. The next morning, you find yourself waking up and discovering that you beat your alarm clock by just a minute or two.

What’s going on here? Is it pure luck? Or perhaps you have some uncanny ability to wake up at the right time without help?

It turns out that many people have come to Dr. Robert Stickgold over the years expressing wonder about this phenomenon.

“It’s one of those questions in sleep studies where everyone in the field seems to agree that obviously can’t be true,” says Stickgold, a cognitive neuroscientist at Harvard Medical School and Beth Israel Deaconess Medical Center.

Stickgold even remembers bringing it up to his mentor when he started in the field — only to be greeted with a suspicious look and a far from satisfactory explanation. “I can assure you that all of us sleep researchers say, ‘Balderdash, that’s impossible,'” he says.

And yet Stickgold still believes there is It’s something. “This kind of accurate awakening is reported by hundreds and thousands of people,” he says, including himself. “I can wake up at 7:59 and turn off the alarm clock before my wife wakes up.” At least, sometimes. .

Of course, it is well known that humans have an elegant and complex system of internal mechanisms that help our bodies keep time. Shaped in part by our exposure to sunlight, caffeine, food, exercise and other factors, these processes regulate our circadian rhythms throughout the roughly 24-hour cycle of day and night and affect when we go to sleep and wake up.

If you get enough sleep and your lifestyle aligns with your circadian rhythm, you should generally wake up at the same time each morning, adjusting for seasonal differences, says Philip Gehrman, a sleep scientist at the University of Pennsylvania.

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But that still doesn’t adequately explain the phenomenon of waking up just minutes before your alarm, especially when it’s a time that deviates from your normal schedule.

“I hear it all the time,” he says. “I think anxiety about being late is contributing.”

Scientists are intrigued — with mixed results

Indeed, some scientists have looked into this mystery over the years, with admittedly, mixed results.

For example, a small, 15-person study from 1979 found that, over two nights, subjects were able to wake up within 20 minutes of the goal more than half the time. The two subjects who did best were followed for the next week, but their accuracy declined rapidly. Another small experiment allowed participants to choose when they woke up and concluded that about half of the spontaneous awakenings they recorded were within the seven minutes of choice before going to sleep.

Other researchers have taken a more subjective approach, asking people to report whether they have the ability to wake up at a certain time. In one such study, more than half of respondents said they could do it. In fact, Stickgold says it’s quite possible that “like many things we think we do all the time, we only do it once in a while.”

OK, so the scientific evidence isn’t exactly overwhelming.

But thanks to Dr. Phyllis Gee, chief of sleep medicine at Northwestern University Feinberg School of Medicine, there was an interesting line of evidence that caught my eye.

Stress hormones may play a role

In the late 90s, a group of researchers in Germany wanted to know how the expectation of waking up affects what is known as the HPA axis – a complex system in the body that deals with our response to stress and involves the hypothalamus, pituitary gland. and adrenal glands.

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Jan Bourne, one of the authors of the study, said they knew that levels of a hormone called ACTH stored in the pituitary gland begin to rise before you habitually wake up, signaling the adrenal glands to release cortisol, a so-called “stress hormone” that helps wake you up. By, among other things.

“In this context, we decided to try it and it actually came out as a hypothesis,” said Born, who is now a professor of behavioral neuroscience at the University of Tübingen in Germany.

Here’s what Born and his team did: They found 15 people who typically woke up around 7 or 7:30 a.m., put them in a sleep lab, and took blood samples over three nights.

The subjects were divided into three different groups: five of them were told that they had to get up at 6 a.m.; Others were assigned 9 a.m.; A third group was given a 9am wake-up time, but then unexpectedly woke up at 6am

Bourne says that as their waking hours approached, a clear difference appeared.

Subjects who were expected to wake up at 6 a.m. had significantly increased ACTH concentrations, starting around 5 a.m. as if their bodies knew they had to get up earlier, Bourne said.

“It’s a well-adapted preparatory response of the organism,” says Born with a smile, “because then you have enough energy to fight the rise and you can make it until you get your first coffee.”

The same increase in stress hormones before waking up was not recorded in the group members who did not plan to wake up early, but were surprised by the 6 a.m. wake-up call. A third group—those scheduled to wake up at 9 a.m.—didn’t have an increase in ACTH an hour before waking (Bourne says it was too late in the morning to see the same effect.)

The birth test didn’t actually measure whether people would eventually wake up on their own before a predetermined time, but he says the results raise some intriguing questions about that phenomenon. After all, how did their bodies know to get up earlier than usual?

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“It tells you that the system is plastic, that it can adapt to changes over time,” he says. And it also suggests that we have some ability to exploit this “system” in our waking state. The idea isn’t completely foreign to the field of sleep research, he says.

A “scientific mystery” is yet to be solved

“It’s well known that there’s a mechanism in the brain that you can deliberately use to influence your body, your brain, during sleep,” Bourne says. He points to research showing that a hypnotic suggestion can help someone sleep more deeply.

Northwestern’s Gee says there are likely “multiple biological mechanisms” that could explain why some people seem to be able to wake up at a certain time without an alarm clock. It’s possible that anxiety about getting up is “overriding” our master internal clock, she says.

“This paper is really neat because it shows that your brain is still working,” she says.

Of course, how exactly it’s working and how much you can rely on this mysterious internal alarm system remains a big, unanswered question. And while none of the sleep researchers I spoke with plan to ditch their alarm clocks, Harvard’s Stickgold says he’s not ready to dismiss the question.

“It’s a real scientific mystery,” he says, “that we have a lot of.” And as in many cases, he added, when faced with a mystery, it would be arrogant “since we don’t know how it could happen, it couldn’t happen.”

This story is part of NPR’s periodic science series “Finding Time — A Journey Through the Fourth Dimension to Learn What Makes Us Tick.”

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