BODY CLOCKS, LIGHT, SLEEP AND HEALTH by Russell Foster
Our lives are ruled by time and we use time to tell us what to do. But the digital alarm clock that wakes us in the morning or the wrist-watch that tells us we are late for supper are unnatural clocks. Our biology answers to a profoundly more ancient beat that probably started to tick early in the evolution of all life. Embedded within our genes, and almost all life on earth, are the instructions for a biological clock that marks the passage of approximately 24 hours. Biological clocks or “circadian clocks” (circa about, diem a day) help time our sleep patterns, alertness, mood, physical strength, blood pressure and much more. Under normal conditions we experience a 24-hour pattern of light and dark, and our circadian clock uses this signal to align biological time to the day and night. The clock is then used to antici-pate the differing demands of the 24-hour day and fine-tune physiology and behaviour in advance of the changing conditions. Body temperature drops, blood pressure decreases, cognitive performance drops and tiredness increases in anticipation of going to bed. Whilst before dawn, metabolism is geared-up in anticipation of increased activity when we wake.
Few of us appreciate this internal world, seduced by an apparent freedom to sleep, work, eat, drink, or travel when we want. But this freedom is an illusion; in reality we are not free to act independently of the biological order that the circadian clock imparts. We are unable to perform with the same efficiency throughout the 24h day. Life has evolved on a planet that experiences profound changes in light over the 24h day and our biology anticipates these changes and needs to be exposed to the natural pattern of light and dark to function properly. Yet we detach ourselves from the environment by forcing our nights into days using electric light, and isolate ourselves in buildings that shield us from natural light.
Russell Foster is Professor of Circadian Neuroscience and the Head of Department of Ophthalmology at Oxford University. Russell Foster’s research spans basic and applied circadian and photoreceptor biology. For his discovery of non-rod, non-cone ocular photoreceptors, he has been awarded numerous prizes, including the Honma prize (Japan), Cogan Award (USA) and Zoological Society Scientific & Edride-Green Medals (UK). He is coauthor of Rhythms of Life and Seasons of Life, popular science books on biological rhythms. In 2008, he was elected as a Fellow of the Royal Society.