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Effects of light on sleep cycles
November 4, 2014, 11:59 am

Lighting, whether natural or artificial, affects all life on our planet. In humans, it plays a crucial role in regulating our circadian rhythm, one of the natural biorhythms that govern the proper functioning of the body. 

Circadian rhythms, also called the body clock, are self-sustained natural mechanisms that adjust to external stimuli arising from the local environment, one of the most important of which is daylight. Driven by daylight, the human body has evolved to adjust its sleep-wake cycle to differing daylight lengths during the seasons.

However, our circadian rhythm is not naturally in sync with our artificial clock. Instead it is a little slower running for 24 hours and 30 minutes on average. This means we are naturally inclined to sleep and wake 30 minutes later each day. If this slower rhythm is not regulated then by the end of the week our sleep/wake cycle could be off by more than 2 hours and we would be hitting that snooze button quite frequently.

Our modern 9 to 5 lifestyle means we may be getting too little sleep during the working week and lying in at the weekends. Longer sleep at the weekend may compensate for the lack of rest during the week, but can reset a later circadian rhythm the following week, resulting in that ‘Sunday morning blues’ feeling.

While alarm clocks offer one way to manage the time lag created by our naturally slower circadian rhythm, a recent white paper published by Philips, the leader in lighting solutions, reveals that a specific quality of light hitting the photoreceptors in our eyes not only regulates our internal body clock, but can actually reset it every single day.

High intensity artificial blue-rich light has been shown to be capable of resetting our body clock because of its qualitative resemblance to natural morning light. Exposure to blue-rich morning light can speed up our circadian rhythm to wake us up earlier and improve the daily functioning of people with an early morning lifestyle.

Professor Derk Jan Dijk, a lighting expert at the University of Surrey says, “Dimming lights a few hours before bedtime facilitates a more rapid onset to sleep and it will prevent your body clock from being shifted to later hours. If you want to shift your clock to earlier hours it is good to be exposed to light and specifically high intensity blue-rich light, when you wake up.”

Companies are currently testing and developing a series of energy efficient lighting products for homes, offices, schools and hospital environments that can variously improve alertness, productivity, calm, sleep and mood.


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