circadian circle and sleep



  • Hi everyone, I work a lot on computer. And I remark that I can't find sleep before midnight. Do you think that I should make my "custom colors" with less blue light in the day ? I mean that f.lux doesn't block blue light in the most part of the day in his "recommanded colors" so I absorb like 7h of blue light.
    I want your advice if it's possible.


  • f.lux team

    Blue light during the day helps set your clock to daytime. If you avoid it you will probably stay up later.



  • There are many reasons a person who works on a computer all day may find it difficult to sleep at night. Conjecture such as "if you avoid it you will probably stay up later" falls into the category of pseudoscience. F-lux produce a program that adjusts the colour levels on your screen, they are not "sleep scientists" and you may note the program uses phrases such as "Light is making your body earlier/later" with an expectation that people will instinctively understand the meaning.

    If I say to you, "you're running a bit late, aren't you?", rhetorically, I could mean any number of things, from mild surprise or to annoyance at someone's tardiness etc, or, I could be sarcastically insulting your intelligence. Context and explanation are important but, unfortunately, you will find little of that here.

    Talk to a doc if you struggle to get to bed early, they might recommend exercise or other different activities including just being in bed with your eyes closed, even if you can't get to sleep. Here is not the place to find answers.


  • f.lux team

    Hi @lastres - we have been studying this topic and actively participating in the research for more than 8 years. Generally this field is called "circadian photobiology" or "chronobiology". Sleep scientists do not study the exact doses of light that affect circadian function, but the fields are indeed getting much closer together than they were even a decade ago, so many sleep scientists are aware of circadian research in humans, and vice-versa.

    In plain terms, this idea is that the body needs enough contrast between day and night (day is way brighter than nighttime) to tell which is which. And most people need to see light both in the morning and in the early evening to keep their circadian clock stable from day to day. If you see more light in the evening, you'll tend to set your clock later, and if you see more in the morning, the reverse - you'll set it earlier.

    In less plain terms, we are trying to explain the PRC ("phase response curve") to light, which is also depicted in our main graph in the f.lux UI. You can read more about it here: https://www.circadiansleepdisorders.org/info/PRC.php



  • hello guys,

    There are many types of circadian rhythms, including daily fluctuations in body temperature, blood pressure, alertness, and melatonin. Our sleep-wake cycle is an essential circadian rhythm that serves as the foundation for our daily well-being. The sleep-wake cycle is approximately 24 hours.

    thanks and regards