Please go to bed by 11:00 pm at the latest. The ideal is until 10 pm. If you sleep for the same 8 hours, it is better for your health to sleep at 10 pm and wake up at 6 am than to sleep at 1 pm and wake up at 9 am. (Some people say that even constipation has healed when they go to bed at 10 pm).
Sleep patterns have a very profound effect on hormone secretion. The human body produces many hormones, but each one does not work independently, but in harmony with the other hormones, it controls the magnificent music of the human body, just as an orchestra instrument plays a symphony with other instruments.
Growth hormone, corticosteroids, and thyroid hormones are particularly closely related to immune function. The timing of sleep is important for them to be properly secreted and to work well.
Growth hormone peaks in secretion from 11:00 pm to 3:00 am, especially 3 hours after bedtime. Also, if the blood sugar level is high, the secretion will slow down. Therefore, the ideal is to finish dinner by 6:30 pm, not to go to bed immediately, and to go to bed more than a couple of hours after your blood sugar drops, that is, around 9 or 10 pm. Growth hormone not only promotes the growth of children but is also secreted even at the age of over 90 and has various functions.
Growth hormone also promotes the conversion of the thyroid hormone T4 (tetraiodothyronine) to T3 (triiodothyronine). T3 is highly bioactive, and if it is not produced well, metabolism slows down and, of course, immune function declines.
In the adrenal cortex corticosteroids — aldosterone, cortisol, androgen — are produced. Especially cortisol is important to fight stress that reduces our immune function. This hormone is secreted in proper quantities from dawn within 1 hour after waking up. Dawn means from around 4 am. In other words, if we stay up late and go to bed around 1 or 2 am, the secretion of this hormone will be disturbed.
However, some people may not be able to go to bed by 10 pm due to many works. But still please go to bed by midnight, get up early, and do the rest of the work in the morning. Any illness can be very incurable if you stay up late. It is no exaggeration to say that people who go to bed after 2 am will not be cured of their illness. This is because many hormones work synergistically, and since ancient times humans have been programmed to wake up at sunrise and rest at sunset. It would take tens of thousands of years for humans to change sleep rhythm and evolve to stay healthy even going to bed after 2 am.
To become a monk of Zen Buddhism and other Buddhist sects, young people need very hard training and ascetic practice. Time of sleep is sometimes only 4 hours. But they go to bed at 11 pm and get up at 3 am. They sleep during the most important time for keeping healthy. Traditionally they know the crucial sleep timing for the human body.