by Maybe this happens to you sometimes too:
You go to bed with some morning obligation in mind, maybe a flight to catch or an important meeting. The next morning, you wake up alone to find that you’ve only rung your alarm a minute or two.
What is happening here? Is it pure luck? Or do you have some uncanny ability to wake up right on time without help?
It turns out that many people have come to Dr. Robert Stickgold over the years and wondering about this phenomenon.
“This is one of those questions in the study of sleep where everyone in the field seems to agree that what is apparently true could not be,” says Stickgold, who is a cognitive neuroscientist at Harvard Medical School and the Beth Israel Deaconess Center.
Stickgold even remembers mentioning it to his mentor when he was just starting out in the field — only to be greeted with a dubious look and a less-than-satisfying explanation. “I can assure you that all of us sleep researchers say, ‘bald, that’s impossible,'” he says.
And yet Stickgold still thinks there’s something to it. “This kind of precision 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 before my wife wakes up.” At least, sometimes.
Of course, humans are known to have an elegant and complex system of internal processes that help our bodies keep time. Somewhat shaped by our exposure to sunlight, caffeine, meals, 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 go to sleep and wake me up.
If you’re getting enough sleep and your lifestyle is aligned with your circadian rhythms, you should usually wake up at the same time every morning, adjusting for seasonal differences, says Philip Gehrman, a sleep scientist at the University of Pennsylvania.
But that still doesn’t adequately explain this phenomenon of waking up exactly a few minutes before your alarm, especially when it’s a time that deviates from your normal schedule.
“I hear that all the time,” he says. “I think it’s that anxiety about the delay that’s contributing.”
Scientists are getting curious – with mixed results
In fact, a number of scientists have looked into this conundrum over the years, with admittedly mixed results.
For example, a tiny study of 15 people from 1979 found that, over the course of two nights, people were able to wake up within 20 minutes of the target more than half the time. The two people who did best were then tracked for another week, but their accuracy quickly dropped. Another small experiment allowed participants to choose when to get up and concluded that about half of the spontaneous awakenings were within seven minutes of the choice they had recorded before falling asleep.
Other researchers have taken more subjective approaches, asking people to report whether they are able to wake up at a particular time. In one such study, more than half of respondents said they could do this. Indeed, Stickgold says it’s very likely 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 interesting line of evidence that caught my eye, thanks to Dr. Phyllis Zee, chief of sleep medicine at Northwestern University’s Feinberg School of Medicine.
Stress hormones may play a role
In the late 90s, a group of researchers in Germany wanted to understand how waiting to wake up affected what is known as the HPA axis – a complex system in the body that deals with our stress response and includes the hypothalamus, pituitary . and the adrenal glands.
Jan Born, one of the study’s authors, says they knew that levels of a hormone stored in the pituitary gland, called ACTH, start to rise before the time you usually wake up, which in turn signals the adrenal glands. to release cortisol. a so-called “stress hormone” that helps you wake up among other things.
“In that context, we decided to try it, and it actually worked out as it was supposed to,” 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 normally 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 would have to get up at 6 in the morning. Others were assigned at 9 A.M. the third group was given a wake-up time of 9am, but then unexpectedly woke up at 6am.
Born says a clear difference emerged as the wake-up time approached.
Subjects who waited to wake up at 6am had a marked increase in ACTH concentration starting around 5am. It was as if their bodies knew they needed to wake up earlier, Born says.
“This is a good adaptive preparatory response of the body,” Born says with a laugh, “because then you have enough energy to cope with getting up and you can make it until you drink your first coffee.
The same rise in pre-waking stress hormones was not seen in group members who did not plan to wake up early but were surprised with a 6am wake-up call. The third group—the one assigned a 9 a.m. wake-up time—didn’t have a sharp rise in ACTH an hour before getting up (Born says this 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 interesting questions about this phenomenon. After all, how did their bodies know they should get up earlier than normal?
“It tells you that the system is plastic, it can adapt, on its own, to changes over time,” he says. And it also suggests that we have some ability to exploit this “system” while we are awake. This idea is not entirely foreign to the field of sleep research, he says.
A “scientific mystery” that has not yet been solved
“It’s widely known that there’s a kind of mechanism in the brain that you can use voluntarily to influence your body, your brain, while you’re asleep,” says Born. He points to research showing that a hypnotic suggestion can help someone sleep more deeply.
Zee at Northwestern says there are probably “multiple biological systems” that could explain why some people seem able to wake up without an alarm at a given time. It’s possible that worrying about getting up somehow “bypasses” our master internal clock, he says.
“This paper is really neat because it shows that your brain is still working,” he says.
Of course, how exactly it works and to what extent you can rely on this enigmatic 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, “of which we have a lot.” And as in many fields, he adds, when faced with a mystery, it would be presumptuous “to assume that since we don’t know how it could happen, that it can’t.”
This story is part of NPR’s periodic science series “Finding Time — a journey into the fourth dimension to learn what makes us tick.” [Copyright 2022 NPR]
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