The observation that people living in cities tend to go to bed later than those living in a rural area with no electricity was made quite a long time ago. The divergence between social (the need to stay up until late and wake up early in the morning) and biological times (when we feel the need to go to sleep and naturally wake up) is called “social jet lag.”
Can this be dangerous? According to this article, the social jet lag may cause partial sleep deprivation on school or work days, poor sleep quality, daytime drowsiness, insomnia, cognitive difficulties, and even obesity. Certainly, it’s no good for you! However, light therapy comes in handy.
How would you know?
Recently an interesting research has been conducted on social jet lag. It examined a correlation between bright light exposure during evening classes and increased alertness among students. A group of 27 young male adults, ranged between 21 and 24 years old, who worked in the morning shift and studied in the evening, were exposed to bright light of 8000 lux (a sunrise/sunset on a clear day being around 400 lux) for 20 minutes at 7:00 PM and 9:00 PM, while the level of their melatonin, the sleep hormone, was measured.
The results were quite interesting: the same light stimulus acts differently depending on the timing of the circadian clock. For example, in the group of the so-called “night owl,” the exposure to bright light at 21:00 was sufficient to reduce sleepiness. Furthermore, not only the type of an individual is important, but also timing of the stimulus and its intensity. A 180 lux light exposure is enough to cause a shift in our circadian rhythm, but at the same time no significant change in the alertness was observed with exposure to indoor light, which is around 300 lux.
It appears that the correlation is not linear, meaning that replacing the old bulb with a new one of increased intensity will not necessarily make you stay focused longer in the evening. Perhaps, in the future, different lighting of classrooms during morning, afternoon, and evening classes will be a standard… Until then, we have to take care of ourselves alone. Take naps and use artificial light therapy to increase your performance, both during the day and late into the evening.