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2013-02-26 13:27:09
By James Gallagher Health and science reporter, BBC News
The activity of hundreds of genes was altered when people's sleep was cut to
less than six hours a day for a week.
Writing in the journal Proceedings of the National Academy of Sciences, the
researchers said the results helped explain how poor sleep damaged health.
Heart disease, diabetes, obesity and poor brain function have all been linked
to substandard sleep.
What missing hours in bed actually does to alter health, however, is unknown.
So researchers at the University of Surrey analysed the blood of 26 people
after they had had plenty of sleep, up to 10 hours each night for a week, and
compared the results with samples after a week of fewer than six hours a night.
More than 700 genes were altered by the shift. Each contains the instructions
for building a protein, so those that became more active produced more proteins
- changing the chemistry of the body.
Meanwhile the natural body clock was disturbed - some genes naturally wax and
wane in activity through the day, but this effect was dulled by sleep
deprivation.
Prof Colin Smith, from the University of Surrey, told the BBC: "There was quite
a dramatic change in activity in many different kinds of genes."
Areas such as the immune system and how the body responds to damage and stress
were affected.
Prof Smith added: "Clearly sleep is critical to rebuilding the body and
maintaining a functional state, all kinds of damage appear to occur - hinting
at what may lead to ill health.
"If we can't actually replenish and replace new cells, then that's going to
lead to degenerative diseases."
He said many people may be even more sleep deprived in their daily lives than
those in the study - suggesting these changes may be common.
Dr Akhilesh Reddy, a specialist in the body clock at the University of
Cambridge, said the study was "interesting".
He said the key findings were the effects on inflammation and the immune system
as it was possible to see a link between those effects and health problems such
as diabetes.
The findings also tie into research attempting to do away with sleep, such as
by finding a drug that could eliminate the effects of sleep deprivation.
Dr Reddy said: "We don't know what the switch is that causes all these changes,
but theoretically if you could switch it on or off, you might be able to get
away without sleep.
"But my feeling is that sleep is fundamentally important to regenerating all
cells."
How to get a better night's sleep
A man yawning
Try avoiding key things that make it hard to sleep such as too warm a bedroom
Creating a personal sleep profile can help you manage your body clock
effectively
Sources: Mental Health Foundation and BBC Science
Five things that stop a good night s sleep
Tossing, turning, can't get to sleep? It's a familiar feeling for many. Here
are five things that could be preventing us from getting the restful night we
need.
An uncomfortable or noisy environment
As we start to fall asleep, our muscle tone reduces and our limbs begin to
relax. We may feel drowsy but our brain is still active, and any noise or
discomfort can make it hard to fall asleep.
As we drift into light sleep, an area of the brain called the thalamus starts
to block the flow of information from our senses to the rest of the brain. But
it will still let through noises, which can wake us up.
After about half an hour of light sleep, most of us enter a type of deep sleep
called slow-wave sleep. The changes in the brain neurochemistry typical of deep
sleep, make it harder to be woken up. But some things will always get through -
such as our names being called out loudly.
Missing out on any part of our usual cycle of sleep results in reduced quality
and quantity of sleep.
An irregular routine
We all have a built-in body clock which tells us when we are tired, and helps
synchronise thousands of cells in our body to the circadian rhythm.
The main synchroniser for our body clock is light. Our eyes react to the light
and dark, even when our eyelids are closed.
Daylight prompts our brains to reduce the production of the sleep hormone
melatonin. We become more alert, and wake up.
If we sleep less, because of going to bed late or waking up early, we're
unlikely to get as much deep sleep as we need, or enough of the stage that
comes after it - REM (rapid eye movement) sleep, when we do most of our
dreaming.
Stimulants - coffee, alcohol, food
Continue reading the main story
Stages of sleep
Sleep is essential to maintaining normal levels of cognitive skills such as
speech, memory, and flexible thinking. Sleep plays a significant role in brain
development.
Every 60-100 minutes we go through a cycle of four stages of sleep before
entering dream sleep
Stage 1 is a drowsy, relaxed state between being awake and sleeping
Stage 2 is a period of light sleep where heart rate slows and body temperature
decreases, getting ready for deep sleep
Stage 3 and Stage 4, or deep sleep are hard to wake up from because there is
the lowest amount of activity in your brain and body
After deep sleep, we go back to Stage 2 and then enter dream sleep - also
called REM (rapid eye movement) sleep
Caffeine is a stimulant which can stay in our system for many hours. Drinks
high in caffeine make it harder to fall asleep and can result in more time in
the lighter stages of sleep, with less deep sleep.
Drinking alcohol often makes us snore more, making it harder to breathe, and so
making us more restless.
Although alcohol initially helps some of us fall asleep, too much of it may
disrupt sleep. A lot of alcohol close to bedtime means we can go straight into
deep sleep, missing out on the usual first stage of sleep.
As the alcohol starts to wear off, our bodies come out of deep sleep and back
into REM sleep, which is much easier to wake from.
In the course of a night we usually have six to seven cycles of REM sleep,
which leaves us feeling refreshed. However, a night of drinking means we'll
typically have only one to two, and wake up feeling exhausted.
Eating a large, heavy meal too close to bedtime may also interfere with sleep.
Spicy or fatty foods can cause heartburn, which leads to difficulty in falling
asleep and discomfort throughout the night.
Foods containing a chemical called tyramine (examples include bacon, cheese,
nuts and red wine) can keep us awake at night.
Tyramine causes the release of noradrenaline, a brain stimulant. Carbohydrates,
such as bread or pasta, have the opposite effect. They trigger the release of
hormone serotonin, which makes us sleepy.
The wrong body temperature
Our core body temperature goes down when we sleep. It's controlled by our body
clock, which starts to open up the blood vessels of the hands, face and feet,
to lose heat, as we approach the time we should be sleeping.
But if our bedrooms or duvets are too warm, our bodies can't lose heat. That
can lead to restlessness and discomfort.
Our core temperature should only be half a degree less than during the day. If
we get too cold, we get restless.
A busy mind
Stress is the enemy of sleep. In bed, our mind is left free to wander, and
feeling anxious about getting enough sleep will only make it worse.
In these states people lose track of time. You may nod off and wake up again
but it may still feel as if you are getting no sleep at all. This can result in
fragmented sleep with less time spent in the deep stages of sleep.
Sleep experts recommend getting up and doing an activity which distracts our
mind from worry - such as a puzzle - before trying to sleep again.
Sources: Dr Chris Idzikowski, Director of the Edinburgh Sleep Centre, Professor
Jim Horne, Director of the Loughborough University Sleep Research Centre, Dr
Dev Banerjee, consultant sleep physician.
Illustration: Handsome Frank/Emily Robertson
Sleep profiler