It’s not just the brain that needs sleep

  By the usual definition, sleep refers to a mental state of temporary loss of consciousness. This state is controlled by the brain, the control center is likely to be located in the hypothalamus, and the brain itself is the biggest beneficiary of this state. If you didn’t get a good night’s sleep the night before, you’re sure to be lethargic, have trouble concentrating, and have low thinking skills the next day.
  Lack of sleep also increases the risk of Alzheimer’s disease, new research shows, because after falling asleep, immune cells in the brain begin to clear the “garbage”, the amyloid protein that causes Alzheimer’s disease. If a person stays up too late or has a disordered schedule, this protein builds up in the brain, resulting in neuroinflammation and neuronal death.
  According to the above definition of sleep, only those animals with brains need sleep. Scientists before the 20th century even believed that only mammals needed to sleep. It was not until the beginning of this century that many lower animals also had the habit of sleeping, which broke the “monopoly” of mammals on sleep.
  Going a step further, do brainless animals like nematodes, jellyfish, or hydras need sleep? To answer this question, the definition of sleep must be revised to no longer rely on brain waves, but by measuring how quickly an animal responds to environmental stimuli, and how long it takes to react the next day after sleep deprivation.
  A review on sleep was published in the October 28, 2021, issue of the journal Science, reporting experiments on a jellyfish by a group of scientists at the California Institute of Technology. The jellyfish’s tentacles vibrate constantly, at around 60 vibrations per second during the day, dropping to around 39 per second at night, which seems to mean they’re asleep. The researchers disturbed the jellyfish’s normal sleep with water flow, and the next day they appeared to be sluggish, and the vibration frequency of the tentacles was significantly reduced, much like human behavior after staying up late. Next, the researchers put melatonin into the pool during the day, and the jellyfish’s vibration frequency dropped to the same level as at night, and it seems that the human “sleeping pill” worked in the jellyfish too.
  Jellyfish don’t have a brain, only a few simple nerve cells, which shows that sleep does not require the participation of the brain. Follow-up experiments showed that another type of worm, also without a brain, also sleeps, but they only need to sleep when their metabolic needs are high and stay awake the rest of the time.
  These experimental results suggest that sleep may not have evolved because the brain needs rest, but rather from a metabolic need. In other words, sleep did not originate in vertebrates, but existed when animals first appeared on Earth 500 million years ago. Some scientists even believe that nature evolved not sleep but wakefulness. They believe that when animals first evolved, they were insensitive to environmental changes and that sleeping was their “default setting.” After that, some animals evolved a wakefulness function and began to respond to environmental changes, thus gaining a survival advantage, so the state of wakefulness began to spread in the animal kingdom. But this does not affect the “default setting” of animals, sleep is still a state they must have.
  From these studies, we can draw two important conclusions. First, sleep is related to the body’s metabolism, as in nematodes, for example. Second, sleep is likely related to circadian rhythms, as in jellyfish. Metabolism and circadian rhythms may in turn affect the rhythm and quality of sleep, and we should take advantage of them.
  Take the first item as an example, I believe many people have found that proper exercise is very helpful to improve sleep quality, but which exercise method is the most effective? Dr. Angelique Brentin, an exercise physiologist at Iowa State University, decided to investigate this question. He and colleagues recruited 386 overweight volunteers, many of whom had sleep disturbances. The researchers divided them into 4 groups. The first group did only aerobic exercise (running, swimming, etc.), the second group only did anaerobic strength training (lifting irons), the third group alternated between the two exercises, and the fourth group did what? Do not exercise.
  A year later, the scientists studied the volunteers’ sleep improvements. The best performer was the anaerobic group, which increased effective sleep time by an average of 40 minutes per day. The aerobic group was second, increasing the effective sleep time by an average of 23 minutes per day. This shows that the effect of anaerobic exercise is better than aerobic exercise for improving sleep quality.
  Interestingly, if both types of exercise were done, the effective sleep time only increased by 17 minutes, and the control group without exercise also increased by 15 minutes, indicating that the fitness method of lifting iron first and then running does not have much effect on improving sleep quality. help.
  Dr. Brentin reported the results at the annual meeting of the American Heart Association in early March 2022, which caused quite a stir because it was the largest relevant study to date, and its conclusions are very useful for improving sleep quality. significance.
  The second can also be used to help us improve sleep quality. Phyllis Zey, Ph.D., from Northwestern University School of Medicine, and colleagues designed an experiment to study the effect of room brightness on sleep quality and found that even dim lighting can affect the cardiovascular system and glucose metabolism. Bad effect.
  The researchers recruited 20 healthy young volunteers and randomly divided them into two groups for a controlled trial of the effects of light on sleep. The results showed that sleeping with the lights on did not affect the subjects’ sleep performance, but made them less sensitive to insulin when they woke up the next morning. That is, their bodies need to secrete more insulin to lower blood sugar, and if this continues, they will develop type 2 diabetes, lead to weight gain, and increase their risk of cardiovascular disease.
  The researchers wrote the results into a paper published in the March 14, 2022, issue of Proceedings of the National Academy of Sciences. The article pointed out that there are two sets of nervous systems in the human body, the sympathetic nervous system is mainly responsible for the day, and the parasympathetic nervous system is responsible for the night. When there is plenty of light during the day, the sympathetic nervous system becomes active, causing the heart rate to increase and the person to become more alert. At night, when the light is dim, the parasympathetic nervous system is activated, the heart rate of the person drops, and the metabolic rate also drops, so that the person can sleep better. If the light is still strong at this time, the nervous system will send out the wrong message, leading to metabolic disorders, affecting health.
  More and more people live in cities these days, and many big cities have bright nights, maybe that’s why more and more young people start to gain weight prematurely.
  However, some elderly people need a permanent light in the room because of safety concerns. It is recommended to lower the brightness of the light as much as possible, so that the words on the book cannot be read clearly. If you really need to increase the brightness, it is best to use red light or warm orange light, which is less harmful than white light or blue light.