Stop Waking Up At Night
We've all been there. It's 2am and you are
lying in bed, with a big project or a big decision on your mind. With a
big day to come, you have to get a decent night's rest. Despite you
knowing this, you're still wide awake. You try different strategies for
relaxing. Deep breathing, imagining restful mountain scenery, but
nothing seems to work. This is all typical speciocentric human thinking.
So, if you want a good night's sleep, you need to think more like a
zebra or a walrus.
For the vast majority of species on this
planet, the most upsetting things in life are acute physical crises.
Imagine you are that zebra and a lion has just leaped out and ripped
open your stomach. While you've managed to get away, you now need to
spend the next hour or so evading the lion as it stalks you. But, a
zebra's body physiological response mechanisms are incredibly adapted
for dealing with a short-term physical emergency like this, after which
it's over with you or you're over with it.
Humans react differently. They lie around and worry about stressful
things like mortgages and work, turning on the same physiological
responses that gear us up to fight or flee. This is not an ideal state
of mind or body to be, especially when you want to get some sleep. So
what can you do? A great place to start is to understand your brain when
it sleeps.
Sleep is not a monolithic process. There are different types of sleep:
shallow sleep, in stages one and two, during which you are easily
awakened. After which you have the deep sleep, stages three and four,
also known as a slow-wave sleep. During REM sleep, your eyes dart around
and dreams happen. Your sleep starts off shallow and you gradually
sleep your way down to slow-wave sleep, followed by REM, then back up
again. Then repeat the whole cycle, about every 90 minutes.
The brain works differently in different
stages of sleep, as indicated in studies whereby people were monitored
with a brain scanner, while you measure the levels of activity of
different brain regions. During slow-wave sleep, parts of the brain
associated with arousal activity slow down. As do brain regions involved
in controlling muscle movement. The areas of the brain that first
respond to sensory information have somewhat of a metabolic shutdown,
which creates a metabolically quiescent sleeping brain. But, a very
different picture emerges during REM sleep. Overall, there's an increase
in activity. Some brain regions become even more metabolically active
than they are when you are awake. There is also increased activity in
the limbic system, which is involved in emotion. This is how sleep
generally works. But what happens when you are stressed?
1. No Sleep, More Stress
As we enter into slow-wave sleep, the
sympathetic nervous system keeps us 'wired' relinquishing control to the
parasympathetic nervous system, producing a calm, vegetative state.
This calming effect is reinforced by a decrease in levels of
glucocorticoid, or brain fuel. As you're mobilizing energy to generate
your dream imagery your eyes move rapidly during REM sleep. At which
point glucocorticoid secretion and the sympathetic nervous system rev up
again. But because that slow-wave stage makes up most of what counts as
a good night's rest, sleep is predominantly a time when the stress
response is turned off. Then about an hour before you wake up, levels of
certain 'wake up hormones and glucocorticoids begin to rise. This is
not because rising stress-hormone levels play a role in terminating
sleep.
When you deprive yourself of sleep, the
sleep-induced decline in the levels of those stress hormones has no
chance to occur. Rather, what happens is that glucocorticoids levels
increase and the sympathetic nervous system is activated. During sleep
deprivation, the elevated glucocorticoid levels play a role in breaking
down some of the stored forms of energy in the brain which could have
something to do with why learning and memory are so lousy when you're
sleep-deprived.
In a recent study, they tested one way in
which our brains become impaired when we try to think hard after we
haven't slept. The study conducted tests on a rested subject, using a
brain imager, and asked her to add sequences of three-digit numbers, at
which point her frontal cortex lights up metabolically. But, when
someone was sleep deprived and was given the same math exercise, they
aren't as able to solve the problem. And in this case, the frontal
cortex appeared to be too groggy to compute. In fact, the opposite
occurs: the frontal cortex is activated but so are large parts of the
rest of the cortex.
Of course, we're accustomed to all sorts of
amenities in our modern lives. Some people must also work under
conditions of sleep deprivation, this includes nurses and
round-the-clock technical-support staff. But because we are a nocturnal
species, if a person works at night or works in shifts, regardless of
how many hours of sleep they get, it will still go against their
biological nature. When working these sorts of hours, it tends to
over-activate the stress response. In fact, it should come as no
surprise that night work or shift work increases the risk of
cardiovascular disease, gastrointestinal disorders immune suppression
and fertility problems.
Sleeping habits have changed. In 1910, the average American slept nine
hours a night. We now average 7.5, and that's declining.
2. More Stress, No Sleep
What happens to sleep during stress? The
hormone CRH seems to be responsible. It starts the glucocorticoid
cascade by stimulating the release of another hormone called ACTH from
the pituitary. But it's also the neurotransmitter that activates fear,
anxiety, and arousal pathways in the brain. Unsurprisingly, about three
out of four cases of insomnia are triggered by a major stressor. Studies
have also concluded that poor sleepers tend to have higher levels of
sympathetic arousal or of glucocorticoids in their bloodstream.
Maximum stress can do more than minimize sleep. It can compromise the
quality of the sleep you manage to get. CRH infusion, for instance,
decreases the total amount of sleep by decreasing slow-wave sleep,
exactly the type you need for energy restoration. Rather, your sleep
cycle is dominated by shallow-sleep stages.
This means that you wake up more easily-fragmented sleep. Even the
slow-wave sleep you do get could be disrupted. Ideal slow-wave sleep
shows a characteristic pattern in what is called the 'delta power range'
which can be detected on an electroencephalogram (EEG) recording. If
you are stressed before sleeping, or you are infused with
glucocorticoids during sleep, you get less of that helpful sleep pattern
during slow-wave sleep.
3. Stress Causes Insomnia which Causes Stress...
This can cause some real problems, as a
lack of sleep, or poor-quality sleep activates the stress response and
an activated stress response makes for less sleep or lower-quality
sleep. Each feeds on the other. In one study, it was suggested that the
expectation that you're going to sleep poorly makes you stressed enough
to get poor-quality sleep. In the study, one group of volunteers was
allowed to sleep for as long as they wanted, which was till around 9 am.
But as expected, their stress-hormone levels began to rise at around 8
am. Basically, it would appear that they had enough sleep by about this
time and their brains, felt happily restored and re-energized, and knew
it. They, therefore, started secreting those stress hormones to prepare
to end the sleep.
The second group of volunteers went to sleep at the same time as the
first but were told that they would be woken up at 6 am. So, at 5 am,
their stress-hormone levels also began to rise. What's important to note
here is whether their stress hormones kicked in three hours earlier
than those of the other group because they needed three fewer hours of
sleep? The answer is no.
The rise was due to stressfulness of anticipating being woken up earlier
than desirable. Their brains were feeling that anticipatory stress
while sleeping. This demonstrates that a sleeping brain is still a
working brain. Too little, continuous, uninterrupted sleep, going to
sleep late and getting up early is not good. What's worse? too little
sleep that is unpredictably fragmented. You go to sleep with the
corrosive knowledge that 5 hours or 5 minutes from now the alarm will go
off.
This teaches us a lot about what counts as good sleep and how stress can
prevent it. When it comes to what causes physiological stress, a lack
of predictability and control in your life are the top things you want
to avoid.