Exposure to bright daylight during school time is an important factor in aligning students’ biological clocks with the natural cycle of day and night
The classroom environment typically does not provide sufficient lighting, with the highest levels reaching only 742 lux according to the study (note that in the Czech Republic only 500 lux is required according to the standard). These values are insufficient: the minimum recommended luminance for circadian rhythm regulation is 1000 lux. Therefore, according to the authors, it is necessary to increase the intensity of light exposure during school hours, as pupils are mostly indoors in the morning. Research also shows that even adult workers in offices with plenty of natural light report better sleep compared to those in offices with a lack of it.
Exposure to light in the cyan spectral region in the morning accelerates the circadian phase and optimises sleep timing
The spectral composition of light plays a key role in the regulation of circadian rhythms and should therefore be carefully considered when designing and optimising indoor lighting. Research (Andersen et al., 2012) has shown that sufficient exposure to daylight in the morning from 6 to 10 am is effective in accelerating the circadian phase in most individuals. Conversely, exposure to light in the evening and at night from 6 pm to 6 am can delay the natural sleep-arousal cycle. The results demonstrate that exposure to light in the cyan spectral region in the morning accelerates the circadian phase and optimises sleep timing, while at night it may have the opposite effect and delay the circadian rhythm.
