There is little research into how common this experience is
and why it happens. But it seems to be “a genuine phenomenon” that many people
report, according to Russell Foster, head of the Sleep and Circadian
Neuroscience Institute at the University of Oxford in Britain.
اضافة اعلان
In a telephone survey published in 1997, for instance,
researchers from Iowa and Minnesota randomly interviewed 269 adults mainly in
the Midwest. About three-fourths of those interviewed said they sometimes woke
up before their alarms, and just under one-fourth said they woke up so reliably
that they never had to use an alarm.
After the research team published a newspaper ad asking for
people who always or regularly woke up at specific times without using an
alarm, they invited 15 of those respondents into a lab and tracked their sleep
for three nights. They found that five of the 15 awoke within 10 minutes of
their target wake-up times all three times.
Timing is everything
Nobody knows exactly how or why the body is able to do this,
but researchers say that our biological clocks, which keep track of time, have
something to do with it.
Just above the optic nerve in the brain is a master clock
called the suprachiasmatic nucleus, said Dr Ravi Allada, a neurobiologist who
specializes in sleep and circadian rhythms at Northwestern University.
This clock synchronizes and coordinates our body’s circadian
rhythms, which help us prepare for things that happen at various times of day —
such as falling asleep at night and waking up in the morning.
One way our body does this is by sensing the levels of light
around us, Foster said. Special cells in our eyes detect changing light levels,
such as right before and at dawn — even through our eyelids when our eyes are
closed, he said. These cells probably don’t tell our bodies precisely what time
it is, but they may communicate that we’re approaching the time we normally get
up.
This triggers changes — such as increases in the hormones
cortisol and adrenocorticotropin, as well as in blood pressure, Foster said —
that help us prepare for activity.
What about the times you’ve woken up right before your alarm
when you’ve had to be up much earlier than your body is used to, such as to
catch a flight or attend an important appointment?
Instead of waking up based on what time it is, Allada said,
our bodies may be waking up based on how much time has passed since we went to
bed — working almost like an hourglass. If we go to bed knowing we must be up
in four hours, something may help to ensure that we wake up after four hours.
When things go awry
If our bodies are so good at sensing the time, why do we not
always wake up just before our alarm? And why is it that some people never wake
up before their alarm?
Foster is not sure. It is possible that when you are
especially tired, your body’s need for sleep overrides its biological clock, he
said.
Or sometimes, if you feel nervous about waking up on time,
stress may cause you to wake up earlier than you would like, Allada said.
The bottom line
There are still far more questions than answers about why
and how our bodies sometimes wake us up before our alarms.
But to maximize the chance that you will rouse on time on
your own, Foster said, it can be helpful to set your alarm for the same time
each day so that your body gets used to waking up at a regular time.
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