Light Regulation of Circadian Rhythms: Fact and Fiction and Design Implications

摘要

Almost all life on earth uses an internal biological clock to anticipate the profound changes that result from the Earth's rotation upon its axis. Physiology and behaviour are 'fine-tuned' to the varied, yet predictable, demands of the dayight cycle. We effectively 'know' the time of day, and these internally generated daily cycles are called 'circadian thythms'.1 In addition to the alig nment of the internal and external day, a circadian clock also ensures that biological processes occur in the appropriate temporal sequence. In the active phase, organs need to be prepared for the intake, processing and uptake of nutrients. During sleep, although energy expenditure and digestive processes decrease, many truly essential activities occu r including cellular repair, toxin clearance, memory consolidation and information processing. Indeed, our ability to fu nction du ring the day is dependent upon the quality of our sleep. Our occupation of the night has been possible as a result of the widespread commercialisation of electric light. This extraordinary resource has allowed us to declare war pon the night; our sleep and circadian organisation have been the luckless victims, and the consequences to our performance and health can be serious.