Biological clocks or "circadian clocks" (circa about, diem a day) help time our sleep patterns, alertness, mood, physical strength, blood pressure and much more. The clock is used to anticipate the differing demands of the 24-hour day and fine-tune physiology and behaviour in advance of changing conditions.
In anticipation of going to bed, body temperature drops, blood pressure decreases, cognitive performance declines and tiredness increases. Before dawn, metabolism is geared up in anticipation of increased activity when we wake.
Few of us appreciate this internal world, however. We are seduced by an apparent freedom to sleep, work, eat, drink or travel when we want.
Body clocks differ between people. If you are alert in the mornings and go to bed early you are a "lark", but if you hate mornings and want to keep going through the night, you are an "owl". These differences are partly encoded within our genes but they also change markedly as we age. In our first decade, we tend to wake early, but by the time of puberty bed times and wake times drift to later and later hours.
This tendency to get up later continues until about the age of 19.5 years in women and 21 years in men. At this point there is a reversal and a drift towards earlier sleep and wake times. By the age of 55-60 we are getting up as early as we did when we were 10.
This could explain why young adults really do have a problem getting up in the morning. Teenagers show both delayed sleep and high levels of sleep deprivation because they are going to bed late but still having to get up early in the morning to go to school.
These real biological effects have been largely ignored in terms of the time structure imposed upon teenagers at school. Of the few studies undertaken, later starting times for schools have been shown to improve alertness and the mental abilities of students during their morning lessons.
Paul Kelly, the headmaster of Monkseaton High School near Newcastle, has adopted a later start to the school day and this is having a marked impact, with reduced truanting and improved exam success. Ironically, while young adults tend to improve their performance across the day, their older teachers show a decline in performance over the same period.
We used to think that our 24-hour biological rhythm was driven exclusively by a cluster of 50,000 neurons known as the suprachiasmatic nucleus (SCN), which sits within the hypothalamus at the base of the brain. But isolated cells from almost any organ of the body also express clock genes and proteins. We now appreciate that the SCN acts as a master pacemaker, coordinating the activity of all cellular clocks in a manner that has been likened to the conductor of an orchestra regulating the timing of the multiple and varied components of the ensemble.
Can we act so that we get our natural circadian rhythms back?
I think so.
The advent of the railway brought a new part to our lives - the idea of a standard time. Until then, time had been local. When the sun rose and fell where you lived was the key. Of course back then, there was less connection outside your local so these variances did not matter much.
Life became easier to organize in a machine world. Everything could be scheduled. We think that this is normal.
But think now how work is moving. Millions of us are self employed. What has to be scheduled needs less precision. We don't all have to be at the factory or the office at the same time to be productive.
We work and communicate asynchronously across the entire globe now. While we have to find times to talk directly, this too is less vital.
We have free and easy to acces tech that enables all of this.
Of course we still find standard time useful - - we do need to plan when we do meet or take the plane etc BUT we are much less the prisoner.
So more and more of us can take control of the day and so work on the edges to give us back the night.
Does this work for you?
