All of you probably know what the human 'circadian cycle' is, and depending on your personality, you would either be a night-owl or a morning-lark.

I am interested in understanding the patterns of alertness and tiredness throughout the entire day, between waking up and sleeping.

Personally, my alertness gears up in the morning until 12.30 pm, after which I will, consciously or not, begin to feel very very drowsy. This happens even in the absence of lunch (lunch makes people feel tired because the body works to break down the carbohydrates). I will continue feeling tired and exhausted throughout the entire afternoon before I become alert again from 5 pm onwards. And then of course, in the night I am quite alert.

Here are my questions:

  1. Has research been conducted on this?
  2. Are there strategies to alter the patterns?
  3. Does the tiredness have to do with eating patterns?
  4. What are the relationships between tiredness and our circadian cycles?

1 Answer 1


To answer your questions (as to inspire you to do your own research and to avoid writing a book):

  1. Yes, there is a TON of research on circadian rhythms... There are also many ongoing research projects. I might suggest doing a google scholar search. You might also try getting access to academic peer reviewed journals through your local library, university/college, schools, etc.
  2. There are certainly strategies to alter the patterns. For example, amount of exposure to sunlight and time of day, amount of exercise and time of day, eating patterns, etc. have all been shown to have a correlational effect on wakefulness vs. tiredness. If you do research on what effects our circadian rhythms, you will have an idea of how to alter them. There was an interesting study done on the circadian rhythms of nurses who worked shifts of varying lengths and their work productivity/effectiveness due to their circadian rhythms. You might want to try to find articles like that.
  3. Yes, tiredness can certainly have to do with eating patterns. This is why many schools are implementing breakfast programs for children. Simply, food provides calories which provide energy. Without energy (and energy of the right type) we cannot function to our fullest ability. Different types of food would also effect one's circadian rhythm. You might wish to do some research on ghrelin and the circadian system. There is ongoing research looking into the effect of one's diet on their circadian rhythm.
  4. At this point, the full extent of relationships between tiredness and circadian rhythms are unknown. However, there is strong correlational data which suggests that REM sleep patterns, circadian rhythms and tiredness vs. wakefulness is highly related. You might also wish to look up specific neural circuitry which effects one's circadian rhythms.

I wasn't sure how complex of an answer you wanted or your understanding of neural circuitry, so I haven't typed out the answers for you. Looking up various neurotransmitters would probably be a great place to start if you're interested.


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