Horizon (1964–…): Season 45, Episode 12 - The Secret Life of Your Body Clock - full transcript
Why are you more likely to have
a heart attack at 8.00am?
Or crash your car on the motorway
at two o'clock in the afternoon?
Can taking your medication
at the right time of day
really save your life?
And why should you encourage your
teenager to lie in in the morning?
The answers to these
questions lie in the secret world
of the biological clock.
Most of us are oblivious to them,
but the clocks ticking deep inside
our bodies dominate every moment of
every day of our lives.
We tend to think that we eat
and drink whenever we choose,
but, actually, those behaviours are
very much influenced
by the body clock.
Tonight's Horizon
is a journey inside our bodies
and into this secret world.
Honed through millions of years of
evolution, the body clock
is your guide to what you really
should be doing
at any point in the day.
Modern life tends to abuse internal
time. We have this, this exquisite
system and we just ride over the top
of it and ignore it.
It's extraordinary.
So will you choose to listen to your
body, or suffer the consequences?
If you're running your body
physiology against its natural cycle,
there'll be a price to pay.
24 hours a day, 365 days a year,
our lives on Earth are dominated
by the ticking hand of time.
Atomic clocks and satellites
keep time precisely
across the Earth's surface,
maintaining accuracy to a tenth
of a billionth of a second per day.
But there are some people who are
more interested in a different
sort of clock.
If you've ever thought
how does your body know what time of
day it is,
it's not looking at your watch.
These scientists investigate
the clocks and rhythms
inside our bodies.
They're known as chronobiologists.
That, that is a very complicated one.
Horizon has gathered
together the world's
leading experts in the field.
Oh, yes, yes!
They will give you a unique insight
into how your body works.
There's great advantages to be gained
from understanding how
the body clock works. It's a starting
point for how we engage with
the world.
By bringing together the
latest research in the field,
Horizon has created
the ultimate personal organiser.
This is all the information
that you need
to live life to the maximum.
Hic!
SMASH!
ALARM RINGS
It's the start of the day and,
for most of us,
time to get out of bed,
but across Britain
there's one group
in society who seem to find this
much harder than everybody else.
Welcome to the world of the
teenage zombie,
and the most dysfunctional of
body clocks.
Taylor!
Taylor! Yes. Howay!
Yes.
On the average school day morning,
14-year-old Taylor McCulloch
takes two hours and four alarm
clocks to get out of bed.
Taylor!
If I didn't get him up,
he wouldn't go to school.
He would just lie in bed
until about half past 11
and then get up and say he slept in.
At Taylor's school, headmaster
Paul Kelly has to contend with over
500 teenagers just like him.
What you see around you
in the school is you see
students who don't somehow seem
to be at their best in the morning.
Usually till about 12, I'm a bit
groggy, but after that I'm fine.
I'm just so stubborn,
I just cannot get up in the mornings.
My mam has to come up to my
room and literally shake us.
With parents and teachers across
the country battling with these
morning monsters every day,
could it be that there's more to
teenagers than simply being lazy?
Good morning! Oh!
Could there be a
scientific explanation?
I still can't be bothered at all...
to get up.
The first clues to the mystery
of the teenage lie-in were not
discovered at eight o'clock on a
school day morning,
but 375 feet beneath
the Earth's surface
in a cave deep in the heart
of Texas.
In 1962, self-experimenting
French geologist Michel Siffre
began a series of
ground-breaking studies
in which he lived and worked without
clocks for months at a time
underground.
Siffre lost track of time,
but carefully-recorded data revealed
that his body was keeping a
regular routine of sleeping,
waking and other bodily functions.
It was the first direct proof
that humans have their own
internal time-keeping mechanism,
or body clock.
Many of our most basic drives,
the need to sleep,
the need to eat, the need to drink,
they're not just because we've
not slept or eaten recently.
In fact, it's our body clock telling
us when we need to do these things.
But while we all have an internal
clock, the rhythm of this clock
is not the same for everybody.
Although the average is about 24 and
a quarter hours, some people have, in
fact, a faster clock. At the extreme,
they may have a clock that runs on a
22 hour cycle, whereas other
individuals go the other direction.
They may have a clock that runs
slower and they've got something
like a 25 hour clockwork.
These different cycle lengths
help to explain some of
our most basic behaviour.
Those at the extremes are people
we often refer to as larks and owls.
Larks are those people who
are up early, you know, shorter
body clocks, whereas those who have
a longer clock tend to lag behind
the day/night cycle and tend to be
more owl-like in their behaviour.
I'm a late type, I'm happiest going
to bed late and getting up late.
I'm well used to getting up
at five o'clock in the morning.
I like to go to bed later
and later and wake up later.
I feel great of an evening.
And that's why I'm an academic,
because I don't have to go to work
at eight o'clock in the morning.
But it's not just the length of our
individual cycles
that affect what time we get up in
the morning.
It's our age, too.
We start life being morning types,
but after the age of around about
ten, we tend to drift later and
later through our teenage years,
until our early 20s.
We start to, to go to bed
slightly earlier again.
Finally at the age of 55,
we are going to bed at the time we
were going to bed at the age of ten.
Scientists don't know why age has
such a strong correlation
with the time that we wake up,
but the evidence is the same
all over the world.
Between the ages of around 13
and 21, we consistently get up later
than at any other time in our lives.
It's vindication for Taylor,
and teenagers across the country.
A lot of people think
that teenagers are just lazy.
I'm sure some of them are lazy,
but there clearly is a biological
predisposition for going to
bed late and getting up late.
But is this teenage biology
putting them at a disadvantage
first thing in the morning?
Could the changes in their body
clocks be affecting their education?
Come on! No!
Teenagers across the country
are doing some of the most
important work in their life at times
that don't suit them, and that makes
me worry that we need to address it
and we need to address it quickly.
I want you to think about the
following and it goes like this.
Whether you prefer to actually get
up early in the morning, or whether
you prefer to get up late in
the morning.
In order to find out what time would
best suit his teenagers to learn,
headmaster Paul Kelly is subjecting
the school to a series of tests.
On those sheets of paper,
you will see a list of words.
They're separated
into pairs in a grid.
I'd like you to spend a minute
looking at those words and
memorising as many of those
pairs as you possibly can.
When you're ready, after three...
Pupils will sit two tests,
one in the morning
and one in the afternoon.
These tests have been devised
with the help of Russell Foster,
Professor of Neuroscience
from the University of Oxford.
The prediction would be that as
most teenagers are evening types,
their scores will do better in the
afternoon compared to the morning.
And in exactly the same
way as we did this morning,
I would like you to see how many of
those paired words you can remember.
In the morning they scored 42%
correct answers, and in the afternoon
they scored 51, almost a 10%
improvement just by shifting
something in the time of the day.
Now, these are preliminary data,
but what's exciting is that they
match what's been found in
more detailed studies in both
Canada and the United States.
For Paul Kelly, these
remarkable results signal
the need for radical changes.
In an unprecedented way, teenage
biology could dictate the shape
of his school timetable.
We're looking at having the core of
learning for all students between 11
and 3, and then having
independent learning on both
sides of that, so that they can
do their learning at the time
that's optimal for them.
And really we want to get the
best out of these individuals,
so if we can structure the school
day that fits in with their
temporal biology, then, why not?
It's just so much effort!
By simply paying attention to their
body clocks, it could be possible to
improve the education
and exam results of teenagers
across the country.
APPLAUSE
So, body clock science
has given teenagers licence
to lie in bed all day,
but they're not the only ones who
can benefit by paying attention to
their body clocks. Still to come,
we'll find out why dinner time could
be deadly, and why your grandmother
shouldn't wear sunglasses.
But first you need
to pay attention
to the next few hours of
the morning.
It could be the difference
between life and death.
At this time of the morning,
you will probably be out
of bed and raring to go.
But beware of injecting these
early hours with too much vigour.
The rhythms inside your body are
changing, and these changes could
make you more vulnerable
and exposed than you imagine.
First on the danger list
is blood pressure.
The biggest increase in
blood pressure occurs in the first
three hours
following waking from sleep,
so typically between 7 or 8
and 11 in the morning.
The increase in blood pressure
is more likely to lead to a fatty
deposit on the inside of your
blood vessels breaking off
and blocking the flow of blood to the
heart. That could be disastrous.
The flow of blood to your
heart is further compromised by
a second body rhythm affecting the
flexibility of your blood vessels.
Another factor to do with your blood
is how good your blood
vessels are at widening.
Blood vessels can't widen as much
in the morning compared to
the afternoon and evening.
And when blood vessels can't widen,
there's an increased force on
the blood supply to the heart.
Another factor that changes with
time of day is the stickiness of the
blood, and your blood is more sticky
in the early hours of the morning.
It's got more resistance to
flow at that time.
Sticky blood, increased blood
pressure and stiff vessels...
the peaking of these three
body clock rhythms
at the same time of day leaves your
heart at its most vulnerable.
During the danger hours of 6.00 am
to noon, statistics show
that you are three times more likely
to have a heart attack
than at any other time of day.
For people at risk of a heart attack,
the early morning period is
a danger time for them.
But can those most vulnerable
do anything to reduce this risk?
Five, four, three, two, one...go for
it, Bobby, go on!
Keep it going.
Research carried out by
Greg Atkinson and his team
has shown that if you increase your
activity at the right time of day...
Hard as you can, thirty seconds.
..it can be beneficial.
Ten seconds.
In this experiment,
healthy volunteers
are asked to perform carefully
controlled bouts of exercise.
Four, three, two, one...
OK, back down to 80 watts.
Their blood pressure is monitored
following the exercise session
at five o'clock in the morning,
and an identical session
at seven o'clock in the evening.
OK? Yeah.
HE PANTS
The blood pressure
readings following
each session show a marked
difference.
Exercise in the afternoon leads to a
reduction in blood pressure amounting
to about 10 to 11% reduction,
whereas exercise in the morning
either doesn't change blood pressure
at all, or, in fact, there can be a
slight increase in blood pressure.
By simply changing the
time of day you exercise,
it might be possible to reduce
your blood pressure significantly.
It doesn't have to
be intense exercise.
For a person with already
raised blood pressure,
even walking will, will
cause a reduction in blood pressure.
So, take it easy during
those dangerous morning hours.
It could pay to save your
exertions for after lunch.
It's a great relief
to many of us when you look at your
wristwatch and you see it's 12 noon.
You've survived the
most dangerous part of the day.
At every moment of the 24 hour day,
every part of us is profoundly
influenced by the body clock.
It's not just our physiology that's
controlled by the clock,
it also controls our brains,
when we can think effectively,
when we can concentrate,
when we can be imaginative.
Until about 12 o'clock,
I think I'm sort of really good.
I function best at about mid-morning.
At the end of the day,
catches all my clients unawares.
HE LAUGHS
If you really have to be you know
on the top of your game as it were,
paying good attention to things,
do that type of work between
10 and 12 in the morning.
That's when we're at our best
in terms of thinking.
Scientists are beginning
to understand the rhythms
that are helping our brains power
through those mid-morning tasks.
There are many ways in which
the body clock can control
the functions of our brain
and alertness.
One of them is by controlling the
production of the hormone cortisol,
which has a very powerful
alerting effect on the brain,
and its production is highest in
the morning,
under control of the body clock.
But it won't last for long.
Shortly after lunch time,
most people will experience
a dip in their brainpower.
We're naturally designed to have two
sleeps a day, a big one at night
and another one in the
early afternoon.
It's called a post-lunch dip -
nothing to do with lunch.
It's a natural depression in
our wakefulness, a sort of slump,
and it's made worse if you
had a bad night's sleep.
This natural depression
explains many an office go-slow
across the country
as we fall prey to the micro-sleep.
The afternoon, you usually
take a break, don't you?
If I sit down,
I'll start closing my eyes.
After lunch, it's kind of hard.
Then your eyelids will feel
rather heavy like this and
you sort of wake up for a minute and
you go into these micro-sleeps,
and then you sort of come round
again, look around and you feel a
bit more alert for about a minute
and then it all happens again, and
I think we've all experienced this.
And if you carry on doing
that without stopping it, you will
actually nod off.
But while micro-sleeps are
relatively harmless in the office...
SIREN
..they could spell disaster
on the open road.
Research has shown that 25%
of all motorway crashes are
caused by micro-sleeps,
and you are three times more likely
to fall asleep at the wheel
at two o'clock in the afternoon than
you are at six o'clock
in the evening.
But if you do find yourself
on a motorway at this time of day,
what can you do to avoid the dip?
The best thing to do in that, we've
shown as we've been doing, is take
a large or a couple cups of coffee,
and then you've got 20 minutes,
because the coffee will
take some time to kick in.
What do you do? Fresh air, exercise?
Forget it. Go back to your vehicle
and get your head down
for a quick zizz, a quick 15-minute
nap. It'll be very, very effective.
So, keep safe by drinking coffee
first and then taking your nap.
It will set you up
for the afternoon ahead.
You have survived the dangerous
hours of the early morning,
and the pitfalls of life
after lunch.
As your body moves
into the afternoon, your rhythms
are changing again to prepare you
for the latter part of the day.
These changing rhythms
are controlled by the
central body clock, which is
found deep inside your brain.
No bigger than a grain of rice,
the central body clock
is a bundle of cells controlled by
a unique set of body clock genes.
Over the course of 24 hours,
these clockwork genes regularly
switch themselves on and off,
thereby keeping time and telling
the rest of the body what to do.
The analogy would
be like the conductor of
an orchestra
producing a regular temporal beat
from which the component parts
of the orchestra take their cue,
and as a result, you have a
symphony rather than a cacophony.
This is what the clock in action
actually looks like.
Michael Hastings from the Medical
Research Council has captured
these images by photographing brain
tissue as a ticking body clock genes
switch on and off
over a ten-day period.
As the clockwork goes through
its paces, so the image goes down,
comes back up again,
up down, up down, up down, up down.
When I first saw images like this,
it completely blew me away,
because for the first time
we're able to look inside the
secret world of the clockwork.
That is far more accurate
in time-keeping than just
about any other form of biochemistry.
It really is a profoundly
exquisite mechanism.
And recent breakthroughs have shown
that the master clock in our brains
is not alone.
There are body clocks present in
just about every part of our body,
in the heart, in the lung,
in the liver, in the kidneys.
You name it, it likely has its own
clockwork ticking away inside it.
Understanding the clockwork of
different organs in our bodies has
enabled scientists
to revolutionise the
treatment of disease.
Individual organs can now be
treated according to their own
time schedule, and this could hold
the key to the successful treatment
of a disease so prevalent in the
modern world that one in three of us
will develop a form of it
at some point in our lives.
64-year-old grandmother of 13
Christiane Thievin was diagnosed
with colon cancer in 2004.
IN TRANSLATION: My whole world,
my family, my sister, my mother,
in fact, all my close family
circle were also destabilised.
It was terrible, terrible, terrible.
Until recently,
Christiane received traditional
chemotherapy to treat her cancer.
The aim of chemotherapy
is to kill cancerous tumours
by using toxic drugs.
The problem is that these
drugs also kill healthy cells
and this can leave patients
feeling extremely unwell.
My first chemo sessions affected me
both physically and psychologically.
I went through both.
Physically because I felt...
how can I put it...I felt nauseous
frequently.
I was...how shall I put it...as
if I'd been mutilated somehow,
because I no longer had
honestly any wishes, any needs.
The limited doses of
chemotherapy drugs
that Christiane was
able to tolerate were not
sufficient to shrink her tumours,
and her cancer spread to her liver.
With traditional chemotherapy no
longer an option, Christiane has
come to the Paul Brousse Hospital
outside Paris for an experimental
new treatment which is attempting
to use the natural rhythms
of the body clock to fight
the disease.
The same toxic chemotherapy
drugs are given to Christiane,
but they are carefully scheduled for
times of the day when her healthy
cells are least active, so fewer
of them are damaged by the drugs.
'For me, it's completely,
it's different, it's different.'
I'm feeling well so far.
I'm not, I'm not agitated,
not stressed, not worried.
Instead of spending up to five
days in hospital, Christiane is
fitted with a special portable pump
that will dispense her drugs daily
at four o'clock in the afternoon
and four o'clock in the morning.
Preliminary blood results following
Christiane's first-time treatment
are encouraging.
There is already an improvement
in her liver function tests,
in the marker, tumour marker,
and also the pain that she was
feeling has completely disappeared
after the first treatment.
According to Christiane's doctor,
Francis Levi,
the benefits of administering drugs
at specific times of day
are many-fold.
In a recent study, he found that not
only did the timing of medication
damage five times fewer
healthy cells,
but it was also twice as effective
at killing the cancerous cells.
These early results have given
fresh hope to Christiane,
and could lead to helping
many other patients
for whom no other
treatment was suitable.
I would anticipate
having a normal day.
I'll do a bit of housework,
a bit of cooking,
maybe seeing my grandchildren,
some of my grandchildren,
living in the best way I can.
Understanding how the body clock
influences disease
means that we can develop smarter,
more effective medicines
and medical treatments
which actually exploit
the body clock
as a way into, if you like,
the Achilles' heel of various
disease processes.
But body clock science is not
just about health benefits.
Over the next few hours,
as the afternoon turns into evening,
understanding your body rhythms
can help you enjoy yourself,
whether it's improving
your sex life,
or finding out the
perfect time for a drink.
But before the fun starts,
it's time for a bit of hard work.
The post-lunch slump
is well and truly over,
and it's at this time of day
that your body temperature
and alertness are rising.
You already know that
exercise in the morning
is best avoided for health reasons,
but do you know
when to schedule your work-out
to get the very best performance?
When I exercise,
I like to do it in the morning.
I would say in the evenings.
First thing in the morning.
Morning.
I'd rather do it first thing.
Never!
For the world's top athletes,
choosing the right time of day
for sporting achievement
can be critical.
Cycling's hour record. Renowned
as the sport's toughest challenge,
athletes must cycle as far as
they can in 60 minutes.
The hour record holds a special place
in most people's hearts in cycling
because it's a very pure thing.
It's literally one man
against a clock.
Just pushing yourself
to the physical limit,
and then just holding it
there for an hour.
For Olympic gold medallist and
world champion, Chris Boardman,
it was the ultimate test,
and timing was everything.
Early evening was when
I was always at my best,
and we planned not just the
hour record but training,
the real intense stuff
was done in the evening.
There was less suffering,
if you like.
There was more physical exploration
of how hard I can try,
whereas if you tried to
do the same thing in the morning,
there seems to be no adrenalin,
nothing that's damping down those
senses of pain and discomfort.
Boardman's preference for
evenings comes as no surprise
to sports scientist Greg Atkinson.
Almost every world record in
track and field athletics,
and cycling events,
has been broken
in the afternoon or evening.
In order to find out why
the time of day is so critical,
Atkinson has analysed both
morning and evening performances
of top athletes.
We've done a whole host of studies
trying to break down performance
into its kind of base level
components,
so we've looked
at muscle strength, power,
things like the throwing events.
That peak to trough difference
can be as much as 10%.
Scientists believe that
improved evening performances
are partly down to
temperature fluctuations
caused by the body clock.
Body temperature, like performance,
is highest in the afternoon and
evening than it is in the morning.
And it's thought that this natural
variation in body temperature
acts as a kind of pre-race
or pre-exercise warm-up.
All three of Chris Boardman's
afternoon and evening attempts
at the hour record, were successful.
But not all sports benefit
from this evening high.
The picture becomes
a little bit more complicated
when we look at other performance
components, things like balance,
because balance and
things like hand steadiness
are actually thought to be
highest in the morning.
As more and more components of
sporting performance are analysed,
scientists are
better able to understand
how we can get the very best
out of our bodies.
We think that in
really top-class athletes,
the body clock
will make that difference,
and the sort of differences
that can win Olympic Games
or place you outside of the medals.
With the traditional working
day drawing to a close,
you may feel like
it's time to wind down.
But your body temperature is still
on its natural high,
and your body clock in its
prime time.
So what should you be doing?
The time of day has a
profound effect with alcohol.
If you have a fixed amount of
alcohol at any time of the day,
the level in the blood
will be the same but effects
on the brain will differ.
Alcohol has most effect on the brain
when your body clock
is at its most sleepy.
If you have two units of alcohol
at lunchtime,
i.e., a pint of beer, two shots
of spirit or a glass of wine,
that will make you
sleepy in the afternoon.
You have the same amount of alcohol,
two units, at 7, 8pm,
when the body clock is reaching its
high, you won't notice.
So it's not just how much you drink,
but crucially,
where your body clock is
when you drink it.
So the best time for a drink seems
to be late afternoon, early evening.
That's when we can deal with
the alcohol, enjoy it,
but have a minimum effect
on our cognitive ability.
Clearly if you drink excessive
amounts, you're going to
destroy all that
but it has the least effect
late in the day.
As the evening wears on,
whether you've had a drink or not,
you may be feeling peckish.
A recent survey has revealed
that the average UK family
sits down for their evening meal
just before 8pm.
But should you really be tucking
into a big meal at this time?
Nutritionist Linda Morgan
from the University of Surrey,
is on a mission to find out.
Our eating habits have changed over
the years, over the last 100 years.
We used to eat very big breakfasts
and eat reasonably large lunches
and virtually very little for supper,
and that pattern
has been reversed now.
And we eat most of our calories
actually at supper time.
In order to assess the health
implications of our habit
for late and large suppers,
Linda and her team have analysed
how different daytime
eating patterns affect our bodies.
She gave a group of volunteers
the same meals,
but at different times of the day.
On one occasion we gave them most of
their calories at breakfast time,
and on another we gave them most of
their calories at supper time.
The results of this experiment
showed that even when
calorie intake was identical,
the level of glucose
remaining in the blood
after the evening meal,
was much higher.
Blood glucose levels are an
indication of how efficiently
your body is clearing glucose
and storing it for future use.
And if your blood glucose levels
are quite high after a meal,
that's an indication that you are at
future risk of developing diabetes.
Linda believes that increased blood
glucose levels can be explained
by the body clock rhythm
of the hormone insulin,
which helps to remove glucose
from the blood
and store it elsewhere in the body.
Insulin doesn't work
as well for us at night.
At that time of day, your body
is prepared for sleep.
It's not prepared for eating.
The growing trend for
eating later in the day
is opposed to what our bodies
think we should be doing,
and can have serious consequences
for our health.
I think it's really important that
we eat according to our body clock.
There's an old proverb that says -
eat breakfast like a king,
lunch like a prince,
and dine like a pauper.
If we can eat more of our calories
at breakfast time and at lunch time,
and to eat less at supper time,
then we would be conferring
a real health benefit.
After a day jam-packed
with activity,
your body clock
is beginning to wind down.
As darkness falls, you may be
feeling a little tired
and start to think
about going to bed.
But just as in the morning time,
the larks and owls amongst us
can be running
on very different schedules.
I go to bed sort of ten o'clock.
Two to three, every night.
About 10:30.
Can be one o'clock in the morning.
But there is a way to trick your
body clock into staying in synch
with those around you.
This is because there is
something outside of our bodies
that plays a critical role in
controlling our internal time.
It's got nothing to do
with your alarm clock,
and it's been with us
since the dawn of time.
Light.
It's the single most influential
external factor
affecting the regulation
of your body clock.
The way these light
triggers control the body clock
is that the light passes through
the eye onto the back of the eye.
And then down the nerves
from the eye into the brain.
The light impulses trigger
the release of chemicals
onto the clock cells
and in that way,
that 24 hour cycle is tweaked,
either forwards or backwards,
slower or faster,
to make it exactly 24.
The light that helps us all run
on the same time system
has most impact on the body clock
at particular times of day.
The important parts are really early
in the morning,
or sunrise, and later on in
the evening, or sunset.
And it's getting light
at these times
where your clock is
most sensitive to light.
Exposing yourself to light in the
morning will speed up your clock
and help you to wake up earlier,
whereas light in the evening
will slow it down,
delaying the time
when you start to feel sleepy,
and allow you to be more active
into the night.
Armed with this knowledge,
light can help you to adjust
to the lifestyle you want.
If you're a late type who
wakes much too late,
and never early enough for work,
you should wear sunglasses
from lunchtime on,
and try to get as little light as
possible in the evenings.
For the early people,
who wake up too early,
they can do exactly the opposite.
They can run around with sunglasses
in the entire morning
and try and get
as much light as possible
in the second half of the day.
Now that the sun has set,
your body clock
should be telling you
to schedule some sleep
in your diary.
But for one group in society,
that's easier said than done.
ALARM CLOCK RINGS
I've just been a bad sleeper for
a number of years. I don't know why.
Well, I actually wake up about, sort
of, usually between 4 and 5am.
I wake up in the dark
so I don't know what the time is,
but usually about five o'clock.
Almost a third of all
people over the age of 65
have problems sleeping.
The sleep of an older person,
it's fragmented.
They sleep, and then they wake up,
and they sleep.
Usually in the early morning they
wake up earlier than they want.
If you ask people,
they're not too glad we're waking
up at five or six in the morning.
They prefer to stay asleep for
another hour or so.
Scientists believe that these
sleep problems are connected
to an ageing body clock.
We don't know why the clock is not
working as well in ageing,
but we have a clue from biology on
what's underlying these changes.
And that is that although the number
of brain cells in that clock
is unchanged,
you don't lose the cells,
you see that much less cells
are active.
The problems for an ageing body
clock are further compounded
by the deteriorating state
of elderly people's eyes.
The density of your lens, the
thickness of your lens increases.
It lets less and less light in.
So the less light that we get
coming through the eyes
means that we have less of a
signal going to the body clock,
and so the clock isn't
as synchronised to the daylight
as it used to be when we were young.
Eus van Someren has studied these
desynchronised clocks
in a group of elderly people with
some of the most disturbed
sleep patterns -
those suffering from
Alzheimer's or dementia.
During the night they have
these short bouts of sleep,
not too long - I think seldom
longer than 15 minutes.
So it's very fragmented sleep.
You see that the more fragmented
this sleep-wake pattern is,
the more depressive symptoms,
the more agitation, irritability.
It's having a big
impact on their lives.
For Van Someren, the key to
improving this fragmented sleep
lay in restoring the natural
rhythms of the body clock.
In the biological clock,
cells are still there but not active.
We know that light is
normally activating these cells.
And we thought maybe we
can reactivate these cells
by giving additional light.
Van Someren changed the light
fittings in nursing homes
so that the Alzheimer's patients
were receiving up to three times
more light
during daytime hours.
He then followed their
sleep patterns, mood,
cognitive performance and daily
activities, for over three years.
The results exceeded
all expectations.
We expected changes in sleep-wake
rhythm, but somewhat to our surprise
the effects on other symptoms
were huge as well.
For example, depressive symptoms
were much less.
Cognitive performance, so memory
performance, was much better.
But also doing activities of
daily life, like eating your lunch
or buttoning your shirt,
things like that,
declined much less in the people who
got additional bright light.
It's an impressive
list of improvements,
and matches what can be
achieved with the drugs
that are currently available
to Alzheimer's patients.
The improvement you get with drugs
are comparable
to the improvement you get
with light.
But with the drugs you have
adverse effects, like nausea.
On the contrary, with light, you
also get the improvement of mood.
So you might compare the effect of
light with giving two drugs -
one for cognition, the memory,
and the other one for mood.
It's an important step forward
in the management
of Alzheimer's disease.
But can other elderly people
benefit from light, too?
Ongoing studies in the UK are
testing the impact of light
on healthy elderly people
in their own homes.
We are quite
encouraged by the results.
This might really be a way of
improving sleep, in elderly,
in their own homes,
without sleep medication.
As the relationship between light
and our internal rhythms
is better understood,
so the possibilities open up
of improving all of our lives
by simply harnessing the
natural power of the body clock.
It's well past bedtime,
but for some people,
sleep is the last thing
on their mind.
Is there a best time
of day for having sex?
Not going there!
I've no idea!
Don't wait until midnight, because
by then you will be exhausted.
Studies have shown
that the most common time for sex
is between 11pm and 1am,
but this is largely because this
time is convenient
for both work and family life.
Given the fact that we're having sex
at a time of day which seems to fit
in with our busy work schedules,
and our socialising,
would there be a better,
as it were, biological time?
And the answer is, we don't know.
But there are some ways
we might go forward.
So for example testosterone levels
in the male peak in the morning.
Paradoxically the evidence
suggests that a woman
is more likely to orgasm
if she has sex in the evening
rather than the morning.
So there's a mismatch there.
You might want to consider the
afternoon.
Performance is best in the afternoon
with your body temperature
at maximum.
And another area would
be that skin sensitivity
peaks in the late evening.
It depends on what you have eaten,
if you had alcohol or non-alcohol.
Some people may be more liberated
and have better sex
when they had alcohol.
Other people may be too tired
after alcohol to have it.
So where do we go from here?
Find out yourself.
It's the dead of night,
and our body clocks are
reaching the lowest point
in their 24-hour cycle.
So as we proceed into the night,
core body temperature is dropping.
Blood pressure is dropping.
Blood viscosity,
blood thickness is going up,
and we're generally being prepared
metabolically for the resting state.
And we would reach a low point,
in terms of metabolic activity,
around about 4am.
But even though our biology is
telling us to go to bed,
over four million of us
are up and working.
Studies from all over the world
have shown that this mismatch of
lifestyle and biology
can put our bodies
under enormous strain.
Modern life tends to
ignore the body clock,
we assume we can do whatever
we want, whenever we want,
and that's simply not the case.
The problem is, our bodies rarely
fully adjust to shift work patterns,
leaving them perpetually
out of synch.
We're finding that the
incidence of cancer
is higher in night shift work,
mental health,
cardiovascular disease and a
whole slew of other pathologies.
And I think this is a good example
of where physiology is being
pushed outside its normal range
at that particular time of day.
But whether we are up on the
night shift or not,
this low point in our
body clock cycle
can make us particularly vulnerable.
In old people, or in sick people,
it's literally in the small hours,
the quiet hours between two
and four o'clock in the morning,
when the body's turned down
to its minimum operation,
that's when people tend to
slip off this mortal coil.
But it's not all bad news.
BABY CRIES
Harder, come on, push harder!
Push down. You can do it. Come on!
This time of night is
also the most popular
for one of our body's most
miraculous events.
And again. There we go!
More babies are born naturally
between three and five in the
morning than any other time of day.
Keep it coming!
At that time of night, our
bodies are extremely relaxed.
Body temperature is low,
sensation for pain is lower
and that is a good time
to give birth.
But even from the very first
breath we take...
It's OK, sweetie.
..our natural rhythms are being
influenced by the modern world.
As more women give birth in
hospitals
and experience greater intervention
to natural birth,
these early morning baby rhythms
have become less pronounced.
As our 24 hours comes to an end,
your body clock comes full cycle.
The diary for your perfect day
is complete.
Body clock science has shown you
how to do what your body wants
at every hour of the day.
It's now up to you whether you
choose to follow your clockwork.
I think disregarding our body clock
is foolish at every level.
It's a beautifully orchestrated
clock within our brain
that's activating a
whole slew of different systems.
The body clock really is a fantastic
piece of biological machinery.
Because it controls what
we do and how well we do it,
knowing how it works, we can
really turn it to our own advantage.
If you work against them, then
you're pushing the string uphill.
You're really not going to get
as far as you otherwise would.
So go with the flow, as it were.
Work with the clock.
a heart attack at 8.00am?
Or crash your car on the motorway
at two o'clock in the afternoon?
Can taking your medication
at the right time of day
really save your life?
And why should you encourage your
teenager to lie in in the morning?
The answers to these
questions lie in the secret world
of the biological clock.
Most of us are oblivious to them,
but the clocks ticking deep inside
our bodies dominate every moment of
every day of our lives.
We tend to think that we eat
and drink whenever we choose,
but, actually, those behaviours are
very much influenced
by the body clock.
Tonight's Horizon
is a journey inside our bodies
and into this secret world.
Honed through millions of years of
evolution, the body clock
is your guide to what you really
should be doing
at any point in the day.
Modern life tends to abuse internal
time. We have this, this exquisite
system and we just ride over the top
of it and ignore it.
It's extraordinary.
So will you choose to listen to your
body, or suffer the consequences?
If you're running your body
physiology against its natural cycle,
there'll be a price to pay.
24 hours a day, 365 days a year,
our lives on Earth are dominated
by the ticking hand of time.
Atomic clocks and satellites
keep time precisely
across the Earth's surface,
maintaining accuracy to a tenth
of a billionth of a second per day.
But there are some people who are
more interested in a different
sort of clock.
If you've ever thought
how does your body know what time of
day it is,
it's not looking at your watch.
These scientists investigate
the clocks and rhythms
inside our bodies.
They're known as chronobiologists.
That, that is a very complicated one.
Horizon has gathered
together the world's
leading experts in the field.
Oh, yes, yes!
They will give you a unique insight
into how your body works.
There's great advantages to be gained
from understanding how
the body clock works. It's a starting
point for how we engage with
the world.
By bringing together the
latest research in the field,
Horizon has created
the ultimate personal organiser.
This is all the information
that you need
to live life to the maximum.
Hic!
SMASH!
ALARM RINGS
It's the start of the day and,
for most of us,
time to get out of bed,
but across Britain
there's one group
in society who seem to find this
much harder than everybody else.
Welcome to the world of the
teenage zombie,
and the most dysfunctional of
body clocks.
Taylor!
Taylor! Yes. Howay!
Yes.
On the average school day morning,
14-year-old Taylor McCulloch
takes two hours and four alarm
clocks to get out of bed.
Taylor!
If I didn't get him up,
he wouldn't go to school.
He would just lie in bed
until about half past 11
and then get up and say he slept in.
At Taylor's school, headmaster
Paul Kelly has to contend with over
500 teenagers just like him.
What you see around you
in the school is you see
students who don't somehow seem
to be at their best in the morning.
Usually till about 12, I'm a bit
groggy, but after that I'm fine.
I'm just so stubborn,
I just cannot get up in the mornings.
My mam has to come up to my
room and literally shake us.
With parents and teachers across
the country battling with these
morning monsters every day,
could it be that there's more to
teenagers than simply being lazy?
Good morning! Oh!
Could there be a
scientific explanation?
I still can't be bothered at all...
to get up.
The first clues to the mystery
of the teenage lie-in were not
discovered at eight o'clock on a
school day morning,
but 375 feet beneath
the Earth's surface
in a cave deep in the heart
of Texas.
In 1962, self-experimenting
French geologist Michel Siffre
began a series of
ground-breaking studies
in which he lived and worked without
clocks for months at a time
underground.
Siffre lost track of time,
but carefully-recorded data revealed
that his body was keeping a
regular routine of sleeping,
waking and other bodily functions.
It was the first direct proof
that humans have their own
internal time-keeping mechanism,
or body clock.
Many of our most basic drives,
the need to sleep,
the need to eat, the need to drink,
they're not just because we've
not slept or eaten recently.
In fact, it's our body clock telling
us when we need to do these things.
But while we all have an internal
clock, the rhythm of this clock
is not the same for everybody.
Although the average is about 24 and
a quarter hours, some people have, in
fact, a faster clock. At the extreme,
they may have a clock that runs on a
22 hour cycle, whereas other
individuals go the other direction.
They may have a clock that runs
slower and they've got something
like a 25 hour clockwork.
These different cycle lengths
help to explain some of
our most basic behaviour.
Those at the extremes are people
we often refer to as larks and owls.
Larks are those people who
are up early, you know, shorter
body clocks, whereas those who have
a longer clock tend to lag behind
the day/night cycle and tend to be
more owl-like in their behaviour.
I'm a late type, I'm happiest going
to bed late and getting up late.
I'm well used to getting up
at five o'clock in the morning.
I like to go to bed later
and later and wake up later.
I feel great of an evening.
And that's why I'm an academic,
because I don't have to go to work
at eight o'clock in the morning.
But it's not just the length of our
individual cycles
that affect what time we get up in
the morning.
It's our age, too.
We start life being morning types,
but after the age of around about
ten, we tend to drift later and
later through our teenage years,
until our early 20s.
We start to, to go to bed
slightly earlier again.
Finally at the age of 55,
we are going to bed at the time we
were going to bed at the age of ten.
Scientists don't know why age has
such a strong correlation
with the time that we wake up,
but the evidence is the same
all over the world.
Between the ages of around 13
and 21, we consistently get up later
than at any other time in our lives.
It's vindication for Taylor,
and teenagers across the country.
A lot of people think
that teenagers are just lazy.
I'm sure some of them are lazy,
but there clearly is a biological
predisposition for going to
bed late and getting up late.
But is this teenage biology
putting them at a disadvantage
first thing in the morning?
Could the changes in their body
clocks be affecting their education?
Come on! No!
Teenagers across the country
are doing some of the most
important work in their life at times
that don't suit them, and that makes
me worry that we need to address it
and we need to address it quickly.
I want you to think about the
following and it goes like this.
Whether you prefer to actually get
up early in the morning, or whether
you prefer to get up late in
the morning.
In order to find out what time would
best suit his teenagers to learn,
headmaster Paul Kelly is subjecting
the school to a series of tests.
On those sheets of paper,
you will see a list of words.
They're separated
into pairs in a grid.
I'd like you to spend a minute
looking at those words and
memorising as many of those
pairs as you possibly can.
When you're ready, after three...
Pupils will sit two tests,
one in the morning
and one in the afternoon.
These tests have been devised
with the help of Russell Foster,
Professor of Neuroscience
from the University of Oxford.
The prediction would be that as
most teenagers are evening types,
their scores will do better in the
afternoon compared to the morning.
And in exactly the same
way as we did this morning,
I would like you to see how many of
those paired words you can remember.
In the morning they scored 42%
correct answers, and in the afternoon
they scored 51, almost a 10%
improvement just by shifting
something in the time of the day.
Now, these are preliminary data,
but what's exciting is that they
match what's been found in
more detailed studies in both
Canada and the United States.
For Paul Kelly, these
remarkable results signal
the need for radical changes.
In an unprecedented way, teenage
biology could dictate the shape
of his school timetable.
We're looking at having the core of
learning for all students between 11
and 3, and then having
independent learning on both
sides of that, so that they can
do their learning at the time
that's optimal for them.
And really we want to get the
best out of these individuals,
so if we can structure the school
day that fits in with their
temporal biology, then, why not?
It's just so much effort!
By simply paying attention to their
body clocks, it could be possible to
improve the education
and exam results of teenagers
across the country.
APPLAUSE
So, body clock science
has given teenagers licence
to lie in bed all day,
but they're not the only ones who
can benefit by paying attention to
their body clocks. Still to come,
we'll find out why dinner time could
be deadly, and why your grandmother
shouldn't wear sunglasses.
But first you need
to pay attention
to the next few hours of
the morning.
It could be the difference
between life and death.
At this time of the morning,
you will probably be out
of bed and raring to go.
But beware of injecting these
early hours with too much vigour.
The rhythms inside your body are
changing, and these changes could
make you more vulnerable
and exposed than you imagine.
First on the danger list
is blood pressure.
The biggest increase in
blood pressure occurs in the first
three hours
following waking from sleep,
so typically between 7 or 8
and 11 in the morning.
The increase in blood pressure
is more likely to lead to a fatty
deposit on the inside of your
blood vessels breaking off
and blocking the flow of blood to the
heart. That could be disastrous.
The flow of blood to your
heart is further compromised by
a second body rhythm affecting the
flexibility of your blood vessels.
Another factor to do with your blood
is how good your blood
vessels are at widening.
Blood vessels can't widen as much
in the morning compared to
the afternoon and evening.
And when blood vessels can't widen,
there's an increased force on
the blood supply to the heart.
Another factor that changes with
time of day is the stickiness of the
blood, and your blood is more sticky
in the early hours of the morning.
It's got more resistance to
flow at that time.
Sticky blood, increased blood
pressure and stiff vessels...
the peaking of these three
body clock rhythms
at the same time of day leaves your
heart at its most vulnerable.
During the danger hours of 6.00 am
to noon, statistics show
that you are three times more likely
to have a heart attack
than at any other time of day.
For people at risk of a heart attack,
the early morning period is
a danger time for them.
But can those most vulnerable
do anything to reduce this risk?
Five, four, three, two, one...go for
it, Bobby, go on!
Keep it going.
Research carried out by
Greg Atkinson and his team
has shown that if you increase your
activity at the right time of day...
Hard as you can, thirty seconds.
..it can be beneficial.
Ten seconds.
In this experiment,
healthy volunteers
are asked to perform carefully
controlled bouts of exercise.
Four, three, two, one...
OK, back down to 80 watts.
Their blood pressure is monitored
following the exercise session
at five o'clock in the morning,
and an identical session
at seven o'clock in the evening.
OK? Yeah.
HE PANTS
The blood pressure
readings following
each session show a marked
difference.
Exercise in the afternoon leads to a
reduction in blood pressure amounting
to about 10 to 11% reduction,
whereas exercise in the morning
either doesn't change blood pressure
at all, or, in fact, there can be a
slight increase in blood pressure.
By simply changing the
time of day you exercise,
it might be possible to reduce
your blood pressure significantly.
It doesn't have to
be intense exercise.
For a person with already
raised blood pressure,
even walking will, will
cause a reduction in blood pressure.
So, take it easy during
those dangerous morning hours.
It could pay to save your
exertions for after lunch.
It's a great relief
to many of us when you look at your
wristwatch and you see it's 12 noon.
You've survived the
most dangerous part of the day.
At every moment of the 24 hour day,
every part of us is profoundly
influenced by the body clock.
It's not just our physiology that's
controlled by the clock,
it also controls our brains,
when we can think effectively,
when we can concentrate,
when we can be imaginative.
Until about 12 o'clock,
I think I'm sort of really good.
I function best at about mid-morning.
At the end of the day,
catches all my clients unawares.
HE LAUGHS
If you really have to be you know
on the top of your game as it were,
paying good attention to things,
do that type of work between
10 and 12 in the morning.
That's when we're at our best
in terms of thinking.
Scientists are beginning
to understand the rhythms
that are helping our brains power
through those mid-morning tasks.
There are many ways in which
the body clock can control
the functions of our brain
and alertness.
One of them is by controlling the
production of the hormone cortisol,
which has a very powerful
alerting effect on the brain,
and its production is highest in
the morning,
under control of the body clock.
But it won't last for long.
Shortly after lunch time,
most people will experience
a dip in their brainpower.
We're naturally designed to have two
sleeps a day, a big one at night
and another one in the
early afternoon.
It's called a post-lunch dip -
nothing to do with lunch.
It's a natural depression in
our wakefulness, a sort of slump,
and it's made worse if you
had a bad night's sleep.
This natural depression
explains many an office go-slow
across the country
as we fall prey to the micro-sleep.
The afternoon, you usually
take a break, don't you?
If I sit down,
I'll start closing my eyes.
After lunch, it's kind of hard.
Then your eyelids will feel
rather heavy like this and
you sort of wake up for a minute and
you go into these micro-sleeps,
and then you sort of come round
again, look around and you feel a
bit more alert for about a minute
and then it all happens again, and
I think we've all experienced this.
And if you carry on doing
that without stopping it, you will
actually nod off.
But while micro-sleeps are
relatively harmless in the office...
SIREN
..they could spell disaster
on the open road.
Research has shown that 25%
of all motorway crashes are
caused by micro-sleeps,
and you are three times more likely
to fall asleep at the wheel
at two o'clock in the afternoon than
you are at six o'clock
in the evening.
But if you do find yourself
on a motorway at this time of day,
what can you do to avoid the dip?
The best thing to do in that, we've
shown as we've been doing, is take
a large or a couple cups of coffee,
and then you've got 20 minutes,
because the coffee will
take some time to kick in.
What do you do? Fresh air, exercise?
Forget it. Go back to your vehicle
and get your head down
for a quick zizz, a quick 15-minute
nap. It'll be very, very effective.
So, keep safe by drinking coffee
first and then taking your nap.
It will set you up
for the afternoon ahead.
You have survived the dangerous
hours of the early morning,
and the pitfalls of life
after lunch.
As your body moves
into the afternoon, your rhythms
are changing again to prepare you
for the latter part of the day.
These changing rhythms
are controlled by the
central body clock, which is
found deep inside your brain.
No bigger than a grain of rice,
the central body clock
is a bundle of cells controlled by
a unique set of body clock genes.
Over the course of 24 hours,
these clockwork genes regularly
switch themselves on and off,
thereby keeping time and telling
the rest of the body what to do.
The analogy would
be like the conductor of
an orchestra
producing a regular temporal beat
from which the component parts
of the orchestra take their cue,
and as a result, you have a
symphony rather than a cacophony.
This is what the clock in action
actually looks like.
Michael Hastings from the Medical
Research Council has captured
these images by photographing brain
tissue as a ticking body clock genes
switch on and off
over a ten-day period.
As the clockwork goes through
its paces, so the image goes down,
comes back up again,
up down, up down, up down, up down.
When I first saw images like this,
it completely blew me away,
because for the first time
we're able to look inside the
secret world of the clockwork.
That is far more accurate
in time-keeping than just
about any other form of biochemistry.
It really is a profoundly
exquisite mechanism.
And recent breakthroughs have shown
that the master clock in our brains
is not alone.
There are body clocks present in
just about every part of our body,
in the heart, in the lung,
in the liver, in the kidneys.
You name it, it likely has its own
clockwork ticking away inside it.
Understanding the clockwork of
different organs in our bodies has
enabled scientists
to revolutionise the
treatment of disease.
Individual organs can now be
treated according to their own
time schedule, and this could hold
the key to the successful treatment
of a disease so prevalent in the
modern world that one in three of us
will develop a form of it
at some point in our lives.
64-year-old grandmother of 13
Christiane Thievin was diagnosed
with colon cancer in 2004.
IN TRANSLATION: My whole world,
my family, my sister, my mother,
in fact, all my close family
circle were also destabilised.
It was terrible, terrible, terrible.
Until recently,
Christiane received traditional
chemotherapy to treat her cancer.
The aim of chemotherapy
is to kill cancerous tumours
by using toxic drugs.
The problem is that these
drugs also kill healthy cells
and this can leave patients
feeling extremely unwell.
My first chemo sessions affected me
both physically and psychologically.
I went through both.
Physically because I felt...
how can I put it...I felt nauseous
frequently.
I was...how shall I put it...as
if I'd been mutilated somehow,
because I no longer had
honestly any wishes, any needs.
The limited doses of
chemotherapy drugs
that Christiane was
able to tolerate were not
sufficient to shrink her tumours,
and her cancer spread to her liver.
With traditional chemotherapy no
longer an option, Christiane has
come to the Paul Brousse Hospital
outside Paris for an experimental
new treatment which is attempting
to use the natural rhythms
of the body clock to fight
the disease.
The same toxic chemotherapy
drugs are given to Christiane,
but they are carefully scheduled for
times of the day when her healthy
cells are least active, so fewer
of them are damaged by the drugs.
'For me, it's completely,
it's different, it's different.'
I'm feeling well so far.
I'm not, I'm not agitated,
not stressed, not worried.
Instead of spending up to five
days in hospital, Christiane is
fitted with a special portable pump
that will dispense her drugs daily
at four o'clock in the afternoon
and four o'clock in the morning.
Preliminary blood results following
Christiane's first-time treatment
are encouraging.
There is already an improvement
in her liver function tests,
in the marker, tumour marker,
and also the pain that she was
feeling has completely disappeared
after the first treatment.
According to Christiane's doctor,
Francis Levi,
the benefits of administering drugs
at specific times of day
are many-fold.
In a recent study, he found that not
only did the timing of medication
damage five times fewer
healthy cells,
but it was also twice as effective
at killing the cancerous cells.
These early results have given
fresh hope to Christiane,
and could lead to helping
many other patients
for whom no other
treatment was suitable.
I would anticipate
having a normal day.
I'll do a bit of housework,
a bit of cooking,
maybe seeing my grandchildren,
some of my grandchildren,
living in the best way I can.
Understanding how the body clock
influences disease
means that we can develop smarter,
more effective medicines
and medical treatments
which actually exploit
the body clock
as a way into, if you like,
the Achilles' heel of various
disease processes.
But body clock science is not
just about health benefits.
Over the next few hours,
as the afternoon turns into evening,
understanding your body rhythms
can help you enjoy yourself,
whether it's improving
your sex life,
or finding out the
perfect time for a drink.
But before the fun starts,
it's time for a bit of hard work.
The post-lunch slump
is well and truly over,
and it's at this time of day
that your body temperature
and alertness are rising.
You already know that
exercise in the morning
is best avoided for health reasons,
but do you know
when to schedule your work-out
to get the very best performance?
When I exercise,
I like to do it in the morning.
I would say in the evenings.
First thing in the morning.
Morning.
I'd rather do it first thing.
Never!
For the world's top athletes,
choosing the right time of day
for sporting achievement
can be critical.
Cycling's hour record. Renowned
as the sport's toughest challenge,
athletes must cycle as far as
they can in 60 minutes.
The hour record holds a special place
in most people's hearts in cycling
because it's a very pure thing.
It's literally one man
against a clock.
Just pushing yourself
to the physical limit,
and then just holding it
there for an hour.
For Olympic gold medallist and
world champion, Chris Boardman,
it was the ultimate test,
and timing was everything.
Early evening was when
I was always at my best,
and we planned not just the
hour record but training,
the real intense stuff
was done in the evening.
There was less suffering,
if you like.
There was more physical exploration
of how hard I can try,
whereas if you tried to
do the same thing in the morning,
there seems to be no adrenalin,
nothing that's damping down those
senses of pain and discomfort.
Boardman's preference for
evenings comes as no surprise
to sports scientist Greg Atkinson.
Almost every world record in
track and field athletics,
and cycling events,
has been broken
in the afternoon or evening.
In order to find out why
the time of day is so critical,
Atkinson has analysed both
morning and evening performances
of top athletes.
We've done a whole host of studies
trying to break down performance
into its kind of base level
components,
so we've looked
at muscle strength, power,
things like the throwing events.
That peak to trough difference
can be as much as 10%.
Scientists believe that
improved evening performances
are partly down to
temperature fluctuations
caused by the body clock.
Body temperature, like performance,
is highest in the afternoon and
evening than it is in the morning.
And it's thought that this natural
variation in body temperature
acts as a kind of pre-race
or pre-exercise warm-up.
All three of Chris Boardman's
afternoon and evening attempts
at the hour record, were successful.
But not all sports benefit
from this evening high.
The picture becomes
a little bit more complicated
when we look at other performance
components, things like balance,
because balance and
things like hand steadiness
are actually thought to be
highest in the morning.
As more and more components of
sporting performance are analysed,
scientists are
better able to understand
how we can get the very best
out of our bodies.
We think that in
really top-class athletes,
the body clock
will make that difference,
and the sort of differences
that can win Olympic Games
or place you outside of the medals.
With the traditional working
day drawing to a close,
you may feel like
it's time to wind down.
But your body temperature is still
on its natural high,
and your body clock in its
prime time.
So what should you be doing?
The time of day has a
profound effect with alcohol.
If you have a fixed amount of
alcohol at any time of the day,
the level in the blood
will be the same but effects
on the brain will differ.
Alcohol has most effect on the brain
when your body clock
is at its most sleepy.
If you have two units of alcohol
at lunchtime,
i.e., a pint of beer, two shots
of spirit or a glass of wine,
that will make you
sleepy in the afternoon.
You have the same amount of alcohol,
two units, at 7, 8pm,
when the body clock is reaching its
high, you won't notice.
So it's not just how much you drink,
but crucially,
where your body clock is
when you drink it.
So the best time for a drink seems
to be late afternoon, early evening.
That's when we can deal with
the alcohol, enjoy it,
but have a minimum effect
on our cognitive ability.
Clearly if you drink excessive
amounts, you're going to
destroy all that
but it has the least effect
late in the day.
As the evening wears on,
whether you've had a drink or not,
you may be feeling peckish.
A recent survey has revealed
that the average UK family
sits down for their evening meal
just before 8pm.
But should you really be tucking
into a big meal at this time?
Nutritionist Linda Morgan
from the University of Surrey,
is on a mission to find out.
Our eating habits have changed over
the years, over the last 100 years.
We used to eat very big breakfasts
and eat reasonably large lunches
and virtually very little for supper,
and that pattern
has been reversed now.
And we eat most of our calories
actually at supper time.
In order to assess the health
implications of our habit
for late and large suppers,
Linda and her team have analysed
how different daytime
eating patterns affect our bodies.
She gave a group of volunteers
the same meals,
but at different times of the day.
On one occasion we gave them most of
their calories at breakfast time,
and on another we gave them most of
their calories at supper time.
The results of this experiment
showed that even when
calorie intake was identical,
the level of glucose
remaining in the blood
after the evening meal,
was much higher.
Blood glucose levels are an
indication of how efficiently
your body is clearing glucose
and storing it for future use.
And if your blood glucose levels
are quite high after a meal,
that's an indication that you are at
future risk of developing diabetes.
Linda believes that increased blood
glucose levels can be explained
by the body clock rhythm
of the hormone insulin,
which helps to remove glucose
from the blood
and store it elsewhere in the body.
Insulin doesn't work
as well for us at night.
At that time of day, your body
is prepared for sleep.
It's not prepared for eating.
The growing trend for
eating later in the day
is opposed to what our bodies
think we should be doing,
and can have serious consequences
for our health.
I think it's really important that
we eat according to our body clock.
There's an old proverb that says -
eat breakfast like a king,
lunch like a prince,
and dine like a pauper.
If we can eat more of our calories
at breakfast time and at lunch time,
and to eat less at supper time,
then we would be conferring
a real health benefit.
After a day jam-packed
with activity,
your body clock
is beginning to wind down.
As darkness falls, you may be
feeling a little tired
and start to think
about going to bed.
But just as in the morning time,
the larks and owls amongst us
can be running
on very different schedules.
I go to bed sort of ten o'clock.
Two to three, every night.
About 10:30.
Can be one o'clock in the morning.
But there is a way to trick your
body clock into staying in synch
with those around you.
This is because there is
something outside of our bodies
that plays a critical role in
controlling our internal time.
It's got nothing to do
with your alarm clock,
and it's been with us
since the dawn of time.
Light.
It's the single most influential
external factor
affecting the regulation
of your body clock.
The way these light
triggers control the body clock
is that the light passes through
the eye onto the back of the eye.
And then down the nerves
from the eye into the brain.
The light impulses trigger
the release of chemicals
onto the clock cells
and in that way,
that 24 hour cycle is tweaked,
either forwards or backwards,
slower or faster,
to make it exactly 24.
The light that helps us all run
on the same time system
has most impact on the body clock
at particular times of day.
The important parts are really early
in the morning,
or sunrise, and later on in
the evening, or sunset.
And it's getting light
at these times
where your clock is
most sensitive to light.
Exposing yourself to light in the
morning will speed up your clock
and help you to wake up earlier,
whereas light in the evening
will slow it down,
delaying the time
when you start to feel sleepy,
and allow you to be more active
into the night.
Armed with this knowledge,
light can help you to adjust
to the lifestyle you want.
If you're a late type who
wakes much too late,
and never early enough for work,
you should wear sunglasses
from lunchtime on,
and try to get as little light as
possible in the evenings.
For the early people,
who wake up too early,
they can do exactly the opposite.
They can run around with sunglasses
in the entire morning
and try and get
as much light as possible
in the second half of the day.
Now that the sun has set,
your body clock
should be telling you
to schedule some sleep
in your diary.
But for one group in society,
that's easier said than done.
ALARM CLOCK RINGS
I've just been a bad sleeper for
a number of years. I don't know why.
Well, I actually wake up about, sort
of, usually between 4 and 5am.
I wake up in the dark
so I don't know what the time is,
but usually about five o'clock.
Almost a third of all
people over the age of 65
have problems sleeping.
The sleep of an older person,
it's fragmented.
They sleep, and then they wake up,
and they sleep.
Usually in the early morning they
wake up earlier than they want.
If you ask people,
they're not too glad we're waking
up at five or six in the morning.
They prefer to stay asleep for
another hour or so.
Scientists believe that these
sleep problems are connected
to an ageing body clock.
We don't know why the clock is not
working as well in ageing,
but we have a clue from biology on
what's underlying these changes.
And that is that although the number
of brain cells in that clock
is unchanged,
you don't lose the cells,
you see that much less cells
are active.
The problems for an ageing body
clock are further compounded
by the deteriorating state
of elderly people's eyes.
The density of your lens, the
thickness of your lens increases.
It lets less and less light in.
So the less light that we get
coming through the eyes
means that we have less of a
signal going to the body clock,
and so the clock isn't
as synchronised to the daylight
as it used to be when we were young.
Eus van Someren has studied these
desynchronised clocks
in a group of elderly people with
some of the most disturbed
sleep patterns -
those suffering from
Alzheimer's or dementia.
During the night they have
these short bouts of sleep,
not too long - I think seldom
longer than 15 minutes.
So it's very fragmented sleep.
You see that the more fragmented
this sleep-wake pattern is,
the more depressive symptoms,
the more agitation, irritability.
It's having a big
impact on their lives.
For Van Someren, the key to
improving this fragmented sleep
lay in restoring the natural
rhythms of the body clock.
In the biological clock,
cells are still there but not active.
We know that light is
normally activating these cells.
And we thought maybe we
can reactivate these cells
by giving additional light.
Van Someren changed the light
fittings in nursing homes
so that the Alzheimer's patients
were receiving up to three times
more light
during daytime hours.
He then followed their
sleep patterns, mood,
cognitive performance and daily
activities, for over three years.
The results exceeded
all expectations.
We expected changes in sleep-wake
rhythm, but somewhat to our surprise
the effects on other symptoms
were huge as well.
For example, depressive symptoms
were much less.
Cognitive performance, so memory
performance, was much better.
But also doing activities of
daily life, like eating your lunch
or buttoning your shirt,
things like that,
declined much less in the people who
got additional bright light.
It's an impressive
list of improvements,
and matches what can be
achieved with the drugs
that are currently available
to Alzheimer's patients.
The improvement you get with drugs
are comparable
to the improvement you get
with light.
But with the drugs you have
adverse effects, like nausea.
On the contrary, with light, you
also get the improvement of mood.
So you might compare the effect of
light with giving two drugs -
one for cognition, the memory,
and the other one for mood.
It's an important step forward
in the management
of Alzheimer's disease.
But can other elderly people
benefit from light, too?
Ongoing studies in the UK are
testing the impact of light
on healthy elderly people
in their own homes.
We are quite
encouraged by the results.
This might really be a way of
improving sleep, in elderly,
in their own homes,
without sleep medication.
As the relationship between light
and our internal rhythms
is better understood,
so the possibilities open up
of improving all of our lives
by simply harnessing the
natural power of the body clock.
It's well past bedtime,
but for some people,
sleep is the last thing
on their mind.
Is there a best time
of day for having sex?
Not going there!
I've no idea!
Don't wait until midnight, because
by then you will be exhausted.
Studies have shown
that the most common time for sex
is between 11pm and 1am,
but this is largely because this
time is convenient
for both work and family life.
Given the fact that we're having sex
at a time of day which seems to fit
in with our busy work schedules,
and our socialising,
would there be a better,
as it were, biological time?
And the answer is, we don't know.
But there are some ways
we might go forward.
So for example testosterone levels
in the male peak in the morning.
Paradoxically the evidence
suggests that a woman
is more likely to orgasm
if she has sex in the evening
rather than the morning.
So there's a mismatch there.
You might want to consider the
afternoon.
Performance is best in the afternoon
with your body temperature
at maximum.
And another area would
be that skin sensitivity
peaks in the late evening.
It depends on what you have eaten,
if you had alcohol or non-alcohol.
Some people may be more liberated
and have better sex
when they had alcohol.
Other people may be too tired
after alcohol to have it.
So where do we go from here?
Find out yourself.
It's the dead of night,
and our body clocks are
reaching the lowest point
in their 24-hour cycle.
So as we proceed into the night,
core body temperature is dropping.
Blood pressure is dropping.
Blood viscosity,
blood thickness is going up,
and we're generally being prepared
metabolically for the resting state.
And we would reach a low point,
in terms of metabolic activity,
around about 4am.
But even though our biology is
telling us to go to bed,
over four million of us
are up and working.
Studies from all over the world
have shown that this mismatch of
lifestyle and biology
can put our bodies
under enormous strain.
Modern life tends to
ignore the body clock,
we assume we can do whatever
we want, whenever we want,
and that's simply not the case.
The problem is, our bodies rarely
fully adjust to shift work patterns,
leaving them perpetually
out of synch.
We're finding that the
incidence of cancer
is higher in night shift work,
mental health,
cardiovascular disease and a
whole slew of other pathologies.
And I think this is a good example
of where physiology is being
pushed outside its normal range
at that particular time of day.
But whether we are up on the
night shift or not,
this low point in our
body clock cycle
can make us particularly vulnerable.
In old people, or in sick people,
it's literally in the small hours,
the quiet hours between two
and four o'clock in the morning,
when the body's turned down
to its minimum operation,
that's when people tend to
slip off this mortal coil.
But it's not all bad news.
BABY CRIES
Harder, come on, push harder!
Push down. You can do it. Come on!
This time of night is
also the most popular
for one of our body's most
miraculous events.
And again. There we go!
More babies are born naturally
between three and five in the
morning than any other time of day.
Keep it coming!
At that time of night, our
bodies are extremely relaxed.
Body temperature is low,
sensation for pain is lower
and that is a good time
to give birth.
But even from the very first
breath we take...
It's OK, sweetie.
..our natural rhythms are being
influenced by the modern world.
As more women give birth in
hospitals
and experience greater intervention
to natural birth,
these early morning baby rhythms
have become less pronounced.
As our 24 hours comes to an end,
your body clock comes full cycle.
The diary for your perfect day
is complete.
Body clock science has shown you
how to do what your body wants
at every hour of the day.
It's now up to you whether you
choose to follow your clockwork.
I think disregarding our body clock
is foolish at every level.
It's a beautifully orchestrated
clock within our brain
that's activating a
whole slew of different systems.
The body clock really is a fantastic
piece of biological machinery.
Because it controls what
we do and how well we do it,
knowing how it works, we can
really turn it to our own advantage.
If you work against them, then
you're pushing the string uphill.
You're really not going to get
as far as you otherwise would.
So go with the flow, as it were.
Work with the clock.