Social Jet Lag & Light Therapy
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. It seems intuitive that artificial light enables people to stay alert longer, but apparently this potential benefit can also, in certain cases, be harmful.
Some of the main points of this article are:
- Natural daylight is often not enough to keep students alert, even in the morning classes;
- melatonin levels are measured by taking samples of a patient’s saliva;
- bright light therapy is used to treat seasonal depression, insomnia, and daytime sleepiness.
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.”
Why can this be dangerous? According to the article “Exposure to Bright Light during Evening Class Hours Increases Alertness Among Working College Students,” it may cause partial sleep deprivation on school or workdays, poor sleep quality, daytime drowsiness, insomnia, cognitive difficulties, and even obesity. No wonder scientists are trying to diminish the negative effects of this phenomenon, and most of them are focused on the influence of light.
The impact of light on our circadian rhythm was the subject of multiple studies, but recently an interesting research has been conducted on social jet lag. Its authors examined if there was 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 (unit of illuminance and luminous emittance, with 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 on the circadian clock. This means that, 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, but until then we have to take care of ourselves alone by taking naps and using artificial light therapy to increase our performance, both during the day and late into the evening.