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Slaves to the rhythm

I met up with Russell Foster in 1996 when I was writing a book on the social impact of the 24 hour society. I wanted to know what effect working nights had on human biology and health.

At the time Russell was Reader at Imperial College. Since then he has become professor of circadian neuroscience at Oxford University; a Fellow of the Royal Society; and he has a shelf full of medals from scientific societies around the world. We have written three books together and done our best to popularise the fascinating science of circadian rhythms and their impact on human health and behaviour.

Put simply, while we like to think that we eat when we are hungry, sleep when we are tired, and drink when we are thirsty, it is only a thin veneer of civilisation that gives us the pretence of choice. Left to our natural devices and bereft of our smartphones and alarm clocks, we would tend to eat, sleep, and drink, along with many more biological functions, not when we decide to but when the biological clock inside us tells us to. It is not only our physical behaviours that are dictated by this tyrannical time lord. Our moods and emotions also swing in time to a daily rhythm.

Most of what happens in our bodies, our physiology and biochemistry, is rhythmic, showing strong day–night differences. Heart beat and blood pressure, liver function, the generation of new cells, body temperature, and the production of many hormones such as cortisol and melatonin all show daily changes.

Biological clocks and rhythms can be found everywhere, from bacteria through to fungi, plants, insects, fishes, reptiles, birds, and us. The reason for this ubiquity is clear: all life evolved and lives on a planet that revolves on its axis once a day, and so is exposed to large periods of day and night, light and dark. A trillion dawns and dusks since life began have imprinted a daily rhythm on all living creatures.

The big difference between us and other living things is that to some extent we can cognitively override these ancient hard-wired rhythms. Instead of sleeping as our bodies dictate, we drink another cup of coffee, turn up the radio, roll down the car window and kid ourselves that we can beat a few billion years of evolution. But we pay a price in both our physical and mental well-being.

We beaver away in our offices, shops, and factories, but even a cloudy day outside is some forty times brighter than the artificial light in which we live and work. On a sunny summer day it may be 400 times brighter. Daylight helps us stay healthy because it is the signal that keeps our daily body rhythms ticking over in time with the outside world, in the same way as a watch receives a radio signal that resets it every day to a super-accurate atomic clock.

The big difference between us and other living things is that to some extent we can cognitively override these ancient hard-wired rhythms.

Trouble starts when this alignment breaks down, which may be the problem with Seasonal Affective Disorder (SAD). In Britain about 2-3% of adults suffer from it while a further 10% of have a mild depression known as the winter blues. SAD is perhaps the most common mood disturbance in women of childbearing age in Britain, unremittingly experienced year after year during the six months between the autumnal and vernal equinoxes.

Misalignment of the internal clock may well play a role in a startling list of illnesses including; Bipolar depression, Premenstrual syndrome, Attention deficit disorder (ADDH), Schizophrenia, Chronic fatigue syndrome, Parkinson’s disease, and Alzheimer’s.

The relationship between circadian rhythms and many illnesses, including diabetes; heart disease; strokes; cancer; sleep disorders, is slowly being unravelled. We are some way from new drugs being available, but circadian rhythm research is now in a translational stage, whereby enough is known to suggest therapeutic routes.

A critical area where time of day matters to the individual is the optimum time to take medication, a branch of medicine that has been termed ‘chronotherapy.’ For instance, by varying the timing of medication to the individual, higher doses of anti-cancer drugs can be administered.

We are on the verge of very different medical care for cancer patients, where personalized treatments will be tailored to the most effective time of the day based upon the circadian chronotype of the patient and the timing of cell division within the tumour.

It all makes for an exciting time in circadian rhythm research.

Featured image credit: the eleventh hour disaster by Alexas_Foto. Public domain via Pixabay.

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