Myth: Blue light increases alertness

Myth

If you did not get enough sleep in the night, use coffee, blue light or exercise to improve brain performance

Fact

For great brain performance, there is no substitute for sleep.

Coffee, light or exercise can have some transient effect on how alert we feel. They can also improve learning or mental productivity. However, all those effects are short-lived. Coffee drank on a sleepy brain might actually be unhealthy. Some forms of exercise might also turn out too strenuous. As for the light, its use depends on the timing. Wrong use can be counterproductive, e.g. late in the evening. All those forms of brain "stimulation" should not be used when the brain tries to accomplish the opposite: slow down and perhaps get some sleep.

The best tool for high alertness is healthy sleep in the right phase

The myth of blue light comes from research that shows the importance of light in resetting the sleep phase. If we expose the retina to blue light early in the morning, the sleep phase may shift to earlier hours. As a result, in successive days, we may turn out to be more alert in the morning due to a correction in the circadian cycle. The effect of light on that particular day may be insignificant enough to name the presented myth.

If someone follows the myth and uses the light in the evening to cram for exams, the sleep phase may shift in the opposite direction and reduce morning alertness. This may increase alertness in the evening, but this is rarely a welcome change.

If you are exposed to sunlight in the early morning, you are more likely to stick to healthy sleep hours

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