Horizon (1964) s45e12 Episode Script

The Secret Life of Your Bodyclock

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, onego 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 itI felt nauseous frequently.
I washow shall I put itas 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.
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.
, 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.
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.