The study did not show that the Apple Night Shift function worked

The negative effect of blue light (in the evening) on ​​sleep quality began to be debated in the media sometime in 2016-2017, but it was not until 2018-2019 that anyone with a hole in their mouth began to be an expert on this issue, as the online flood suggests. articles on this topic dated these years. The most juicy are the articles such as “myths and facts”.

The problem is that the whole theory of blue light and the negative effect on sleep quality can be one big myth. As early as December 2019, an article was published in Current Biology that pointed to significant gaps in the theory of blue light and came up with a study showing that brightness (intensity) of light, regardless of color, affects sleep quality rather than color (wavelength). .

At a time when most popular webzines have published their “myths and facts” about blue light explaining how the blue component of light from the display of computers, tablets and mobile phones is responsible for global insomnia, this study has escaped media attention. Perhaps intentionally, because when an author suggests a bad blue light because it’s bad, it’s hard to wait for fourteen days to voluntarily publish an article that fundamentally denies his previous suggestive account. Why not avoid it, especially at a time when manufacturers of all imaging devices are pulling together and also claiming that blue light is bad (because they need to sell a new product with a blue light dimming feature; not because they are doing some studies themselves) . In this context, we can add that in the Czech Republic there are also official recommendations of the Ministry of Health and the Chief Hygienist, which relate to blue light.

Given Timothy Brown’s (and colleagues’s) article in Current Biology, it may come as no surprise that a study by Professor Chad Jensen of Brigham Young University in Utah was similar. He divided the monitored objects (167 people aged 18-24 used to daily use of smartphones) into three groups: The first evening used the Night Shift function (Apple implemented it at the turn of 2016/2017, reduces the share of blue light), the second function did not use and the third she didn’t use a smartphone at all in the evening. However, Jensen did not notice any relevant difference between these groups, and no effect on sleep quality with Night Shift was found.

Jensen further divided the group of subjects into two parts: the first, who slept on average around 7 hours a day, and the second, who slept significantly shorter hours. He found that in the first group (which is closer to the recommended length of sleep), it was possible to observe a higher quality of sleep in people who did not use a smartphone before going to bed than those who used it.

These results are consistent with Timothy Brown’s finding that it is not the wavelength but the (visible) light as such.

Or, a cell-sized device doesn’t produce enough blue light to affect sleep quality. This is assuming that blue light has some effect at all. Naturally, the faint blue light is the last to appear after sunset, when the warm tones disappear from the sky, or move to the very surroundings of the sunset. From this point of view, it seems strange that the cold light that nature offers to man at the end of the day, to which he has adapted his entire evolutionary history, should disrupt sleep processes.

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