Light, whether natural or artificial, affects all life on our planet. It is more than just a source of vitamin D for us humans. Philips has recently compiled in a white paper key insights from more than 10 years of ongoing research about the effects of light on our sleep/wake cycle, or what is known as our “circadian rhythm”. It reveals that the amount and quality of light you are exposed to every day may be responsible for how you feel when you wake, ultimately dictating whether you are more of a morning person or a night owl. Light plays a crucial role in regulating our circadian rhythm, which is one of our natural biorhythms commonly known as our body clock. Our body clock is not naturally in sync with our artificial clock. It is slightly slower, running for 24 hours and 30 minutes on average, which means we are naturally inclined to sleep and wake 30 minutes later each day. If this slower rhythm is not regulated by the end of the week our sleep/wake cycle could be off by more than two hours. Because of our 9 to 5 lifestyle, we may be getting too little sleep during the working week and sleeping in during the weekends. More sleep at the weekend may compensate for any lack of rest, but can reset a later circadian rhythm the following week, resulting in that “Sunday morning blues” feeling.
Artificial light may be used to affect the body clock in the same way that sunlight does. In light therapy, your eyes will be exposing to intense but safe amounts of light for a specific and regular length of time. This light should be similar to that of sunlight in wave length or in quality. The most successful method of shifting one's sleep schedule seems to be exposure to bright light first thing in the morning. This can be achieved by going out in the sunlight, or by sitting in front of a light designed for this purpose (typical room lighting is not nearly enough). It is important to use a light that has the ultraviolet components filtered out, or eye damage can result. The timing of the light exposure is critical. There is a point during the body's sleeping period, such that exposure before that time (for example in the evening) will delay the sleep cycle even further, but exposure after that time (in the morning) will advance it (move it earlier). The closer to that time one gets the light, the more effective it is. The general rule is to sit in front of the light immediately on arising or wakeup in the morning Some have suggested getting up an hour earlier to sit in front of the light, and then going back to sleep. Basically, it is not a good idea to use the lights many hours before your natural wake time, because that risks exposure at a time when it can delay your body clock even further. Instead, move your rise time gradually. For example, get up an hour before your natural rise time and use the lights. Stay on this schedule for several days until your body adjusts to the new rise time. Once you feel comfortable with this, go another hour earlier. In recent years it has been established that blue light is most effective in shifting circadian rhythm, at least for normal sleepers. Light therapy can help someone “re-set” a clock that is off. Regular sleep patterns help to keep the clock set at the new time. Light therapy is only part of a treatment plan that should be guided by a doctor who is familiar with sleep disorders.