A Dream Mystery: What’s Behind ‘Precision Awakening’? : Shots

Humans have an elegant and intricate system of internal processes that help our bodies keep time, and exposure to sunlight, caffeine, and timing of meals all play a part. But that doesn’t take “precision awakening” into account.

Sarah Mosquera/NPR

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Sarah Mosquera/NPR

Humans have an elegant and intricate system of internal processes that help our bodies keep time, and exposure to sunlight, caffeine, and timing of meals all play a part. But that doesn’t take “precision awakening” into account.

Sarah Mosquera/NPR

Maybe this happens to you sometimes too:

You go to bed with some morning obligation on your mind, perhaps a flight to catch or an important meeting. The next morning, you wake up alone to find that you’ve beaten your alarm clock by just a minute or two.

What’s going on here? Is it pure luck? Or maybe you possess some uncanny ability to wake up on time without help?

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

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

Stickgold even remembers bringing the matter up with his mentor when he was just starting out in the field, only to be greeted with a dubious look and a far from satisfactory explanation. “I can assure you that all of us sleep researchers say ‘nonsense, that’s impossible,'” he says.

And yet Stickgold still believes that there is is something to that. “Hundreds and thousands of people report this kind of precision vigilance,” he says, including himself. “I can wake up at 7:59 and turn off the alarm before my wife wakes up.” At least sometimes.

Of course, it’s well known that humans have an elegant and intricate system of internal processes that help our bodies keep time. Somehow shaped 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 this affects when we we go to bed and wake up.

If you get enough sleep and your lifestyle is aligned with your circadian rhythms, you should generally wake up at the same time each morning, adjusting for seasonal differences, he says. Philip Gehrmanna sleep scientist at the University of Pennsylvania.

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

“I hear this all the time,” he says. “I think it’s that anxiety about being late that’s contributing.”

Scientists get curious, with mixed results

Actually, some scientists have investigated this enigma over the years, with mixed results.

For example, a small one, of 15 people to study from 1979 found that, over the course of two nights, subjects were able to wake up within 20 minutes of the target more than half the time. The two subjects that did best were followed for another week, but their accuracy quickly plummeted. Other little experiment he let the participants choose when they would get up and found that about half of the spontaneous awakenings occurred within seven minutes of the choice they had written down before going to sleep.

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

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

But there was an intriguing line of evidence that caught my attention, thanks to Dr Phyllis Zeechief of sleep medicine at Northwestern University Feinberg School of Medicine.

Stress hormones could play a role

In the late 1990s, a group of researchers in Germany wanted to find out how the expectation of waking influenced 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.

january bornone of the study authors, says they knew that levels of a hormone stored in the pituitary gland, called ACTHit begins to rise before your usual wake time, which in turn signals your adrenal glands to release cortisol, the so-called “stress hormone” that helps wake you up, among other things.

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

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

The subjects were divided into three different groups: five of them were told that they would have to get up at 6 am; others were assigned 9 am; the third group woke up at 9 a.m., but then woke up unexpectedly at 6 a.m.

Born says a clear difference emerged as wake-up time approached.

Subjects who anticipated waking up at 6 a.m. had a marked increase in ACTH concentration, beginning around 5 a.m. It was as if their bodies knew they had to get up earlier, Born says.

“This is a good adaptive preparatory response of the body,” says Born with a smile, “because then you have enough energy to get up and last until you have your first coffee.”

That same spike in stress hormones before waking up didn’t register in group members who didn’t plan on getting up early, but were surprised by a 6 a.m. wake-up call. The third group, assigned a 9 a.m. wake-up time, did not have a pronounced rise in ACTH an hour before getting up (Born says that suggests it was simply too late in the morning to see the same effect). .

Born’s experiment didn’t actually measure whether people would eventually wake up on their own before a predetermined time, but he says the findings raise some intriguing questions about that phenomenon. After all, how did their bodies know that they would have to get up earlier than normal?

β€œIt tells you that the system is plastic, it can adapt, per se, to changes over time,” he says. And he also suggests that we have some ability to exploit this “system” while awake. That idea is not entirely foreign to the field of sleep research, he says.

A “scientific mystery” yet to be solved

“It’s well known that there’s a kind of mechanism in the brain that you can use of your own free will to influence your body, your brain, while you sleep,” Born says. He points to research showing that a hypnotic suggestion can help someone fall into a deeper sleep.

Northwestern’s Zee says there are probably “multiple biological systems” that could explain why some people seem able to wake up without an alarm clock at any given time. It’s possible that worrying about getting up is somehow “overriding” our master internal clock, she says.

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

Of course, how exactly it works and to what extent you can trust this enigmatic internal alarm system remains a big unanswered question. And while none of the sleep researchers I spoke to 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, “of which we have a lot.” And as in many fields, he adds, in the face of a mystery, it would be arrogant “to assume that since we don’t know how it could happen, it can’t.”

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

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